/* Copyright (C) 2008-2020 Kentoku Shiba
   Copyright (C) 2019, 2020, MariaDB Corporation.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; version 2 of the License.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */

#define MYSQL_SERVER 1
#include <my_global.h>
#include "mysql_version.h"
#include "sql_priv.h"
#include "probes_mysql.h"
#include "sql_class.h"
#include "sql_partition.h"
#include "sql_table.h"
#include "tztime.h"
#include "spd_err.h"
#include "spd_param.h"
#include "spd_db_include.h"
#include "spd_include.h"
#include "ha_spider.h"
#include "spd_db_conn.h"
#include "spd_trx.h"
#include "spd_conn.h"
#include "spd_table.h"
#include "spd_direct_sql.h"
#include "spd_ping_table.h"
#include "spd_malloc.h"
#include "spd_err.h"

#ifdef SPIDER_HAS_NEXT_THREAD_ID
#define SPIDER_set_next_thread_id(A)
#else
extern ulong *spd_db_att_thread_id;
inline void SPIDER_set_next_thread_id(THD *A)
{
  pthread_mutex_lock(&LOCK_thread_count);
  A->thread_id = (*spd_db_att_thread_id)++;
  pthread_mutex_unlock(&LOCK_thread_count);
}
#endif

extern handlerton *spider_hton_ptr;
extern SPIDER_DBTON spider_dbton[SPIDER_DBTON_SIZE];
extern struct charset_info_st *spd_charset_utf8mb3_bin;
extern LEX_CSTRING spider_unique_id;
pthread_mutex_t spider_conn_id_mutex;
pthread_mutex_t spider_ipport_conn_mutex;
ulonglong spider_conn_id;

extern pthread_attr_t spider_pt_attr;

#ifdef HAVE_PSI_INTERFACE
extern PSI_mutex_key spd_key_mutex_mta_conn;
extern PSI_mutex_key spd_key_mutex_conn_i;
extern PSI_mutex_key spd_key_mutex_conn_loop_check;
extern PSI_cond_key spd_key_cond_conn_i;
extern PSI_mutex_key spd_key_mutex_bg_conn_chain;
extern PSI_mutex_key spd_key_mutex_bg_conn_sync;
extern PSI_mutex_key spd_key_mutex_bg_conn;
extern PSI_mutex_key spd_key_mutex_bg_job_stack;
extern PSI_mutex_key spd_key_mutex_bg_mon;
extern PSI_cond_key spd_key_cond_bg_conn_sync;
extern PSI_cond_key spd_key_cond_bg_conn;
extern PSI_cond_key spd_key_cond_bg_sts;
extern PSI_cond_key spd_key_cond_bg_sts_sync;
extern PSI_cond_key spd_key_cond_bg_crd;
extern PSI_cond_key spd_key_cond_bg_crd_sync;
extern PSI_cond_key spd_key_cond_bg_mon;
extern PSI_cond_key spd_key_cond_bg_mon_sleep;
extern PSI_thread_key spd_key_thd_bg;
extern PSI_thread_key spd_key_thd_bg_sts;
extern PSI_thread_key spd_key_thd_bg_crd;
extern PSI_thread_key spd_key_thd_bg_mon;
#endif

/* UTC time zone for timestamp columns */
extern Time_zone *UTC;

extern sql_mode_t full_sql_mode;
extern sql_mode_t pushdown_sql_mode;

HASH spider_open_connections;
uint spider_open_connections_id;
HASH spider_ipport_conns;
long spider_conn_mutex_id;

const char *spider_open_connections_func_name;
const char *spider_open_connections_file_name;
ulong spider_open_connections_line_no;
pthread_mutex_t spider_conn_mutex;

/* for spider_open_connections and trx_conn_hash */
uchar *spider_conn_get_key(
  SPIDER_CONN *conn,
  size_t *length,
  my_bool not_used __attribute__ ((unused))
) {
  DBUG_ENTER("spider_conn_get_key");
  *length = conn->conn_key_length;
  DBUG_PRINT("info",("spider conn_kind=%u", conn->conn_kind));
#ifdef DBUG_TRACE
  spider_print_keys(conn->conn_key, conn->conn_key_length);
#endif
  DBUG_RETURN((uchar*) conn->conn_key);
}

uchar *spider_ipport_conn_get_key(
   SPIDER_IP_PORT_CONN *ip_port,
   size_t *length,
   my_bool not_used __attribute__ ((unused))
)
{
  DBUG_ENTER("spider_ipport_conn_get_key");
  *length = ip_port->key_len;
  DBUG_RETURN((uchar*) ip_port->key);
}

static uchar *spider_loop_check_full_get_key(
  SPIDER_CONN_LOOP_CHECK *ptr,
  size_t *length,
  my_bool not_used __attribute__ ((unused))
) {
  DBUG_ENTER("spider_loop_check_full_get_key");
  *length = ptr->full_name.length;
  DBUG_RETURN((uchar*) ptr->full_name.str);
}

static uchar *spider_loop_check_to_get_key(
  SPIDER_CONN_LOOP_CHECK *ptr,
  size_t *length,
  my_bool not_used __attribute__ ((unused))
) {
  DBUG_ENTER("spider_loop_check_to_get_key");
  *length = ptr->to_name.length;
  DBUG_RETURN((uchar*) ptr->to_name.str);
}

int spider_conn_init(
  SPIDER_CONN *conn
) {
  int error_num = HA_ERR_OUT_OF_MEM;
  DBUG_ENTER("spider_conn_init");
  if (mysql_mutex_init(spd_key_mutex_conn_loop_check, &conn->loop_check_mutex,
    MY_MUTEX_INIT_FAST))
  {
    goto error_loop_check_mutex_init;
  }
  if (
    my_hash_init(PSI_INSTRUMENT_ME, &conn->loop_checked, spd_charset_utf8mb3_bin, 32, 0, 0,
                   (my_hash_get_key) spider_loop_check_full_get_key, 0, 0)
  ) {
    goto error_loop_checked_hash_init;
  }
  spider_alloc_calc_mem_init(conn->loop_checked, SPD_MID_CONN_INIT_1);
  spider_alloc_calc_mem(spider_current_trx,
    conn->loop_checked,
    conn->loop_checked.array.max_element *
    conn->loop_checked.array.size_of_element);
  if (
    my_hash_init(PSI_INSTRUMENT_ME, &conn->loop_check_queue, spd_charset_utf8mb3_bin, 32, 0, 0,
                   (my_hash_get_key) spider_loop_check_to_get_key, 0, 0)
  ) {
    goto error_loop_check_queue_hash_init;
  }
  spider_alloc_calc_mem_init(conn->loop_check_queue, SPD_MID_CONN_INIT_2);
  spider_alloc_calc_mem(spider_current_trx,
    conn->loop_check_queue,
    conn->loop_check_queue.array.max_element *
    conn->loop_check_queue.array.size_of_element);
  DBUG_RETURN(0);

error_loop_check_queue_hash_init:
  spider_free_mem_calc(spider_current_trx,
    conn->loop_checked_id,
    conn->loop_checked.array.max_element *
    conn->loop_checked.array.size_of_element);
  my_hash_free(&conn->loop_checked);
error_loop_checked_hash_init:
  pthread_mutex_destroy(&conn->loop_check_mutex);
error_loop_check_mutex_init:
  DBUG_RETURN(error_num);
}

void spider_conn_done(
  SPIDER_CONN *conn
) {
  SPIDER_CONN_LOOP_CHECK *lcptr;
  DBUG_ENTER("spider_conn_done");
  uint l = 0;
  while ((lcptr = (SPIDER_CONN_LOOP_CHECK *) my_hash_element(
    &conn->loop_checked, l)))
  {
    spider_free(spider_current_trx, lcptr, MYF(0));
    ++l;
  }
  spider_free_mem_calc(spider_current_trx,
    conn->loop_check_queue_id,
    conn->loop_check_queue.array.max_element *
    conn->loop_check_queue.array.size_of_element);
  my_hash_free(&conn->loop_check_queue);
  spider_free_mem_calc(spider_current_trx,
    conn->loop_checked_id,
    conn->loop_checked.array.max_element *
    conn->loop_checked.array.size_of_element);
  my_hash_free(&conn->loop_checked);
  pthread_mutex_destroy(&conn->loop_check_mutex);
  DBUG_VOID_RETURN;
}

int spider_reset_conn_setted_parameter(
  SPIDER_CONN *conn,
  THD *thd
) {
  DBUG_ENTER("spider_reset_conn_setted_parameter");
  conn->autocommit = spider_param_remote_autocommit();
  conn->sql_log_off = spider_param_remote_sql_log_off();
  conn->wait_timeout = spider_param_remote_wait_timeout(thd);
  conn->sql_mode = full_sql_mode + 1;
  myf utf8_flag= thd->get_utf8_flag();
  if (thd && spider_param_remote_time_zone())
  {
    int tz_length = strlen(spider_param_remote_time_zone());
    String tz_str(spider_param_remote_time_zone(), tz_length,
      &my_charset_latin1);
    conn->time_zone = my_tz_find(thd, &tz_str);
  } else
    conn->time_zone = NULL;
  conn->trx_isolation = spider_param_remote_trx_isolation();
  DBUG_PRINT("info",("spider conn->trx_isolation=%d", conn->trx_isolation));
  if (spider_param_remote_access_charset())
  {
    if (!(conn->access_charset =
        get_charset_by_csname(spider_param_remote_access_charset(),
        MY_CS_PRIMARY, MYF(utf8_flag | MY_WME))))
      DBUG_RETURN(ER_UNKNOWN_CHARACTER_SET);
  } else
    conn->access_charset = NULL;
  char *default_database = spider_param_remote_default_database();
  if (default_database)
  {
    uint default_database_length = strlen(default_database);
    if (conn->default_database.reserve(default_database_length + 1))
      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
    conn->default_database.q_append(default_database,
      default_database_length + 1);
    conn->default_database.length(default_database_length);
  } else
    conn->default_database.length(0);
  DBUG_RETURN(spider_conn_reset_queue_loop_check(conn));
}

int spider_free_conn_alloc(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_free_conn_alloc");
  spider_free_conn_thread(conn);
  spider_db_disconnect(conn);
  if (conn->db_conn)
  {
    delete conn->db_conn;
    conn->db_conn = NULL;
  }
  spider_conn_done(conn);
  pthread_mutex_destroy(&conn->mta_conn_mutex);
  conn->default_database.free();
  DBUG_RETURN(0);
}

void spider_free_conn_from_trx(
  SPIDER_TRX *trx,
  SPIDER_CONN *conn,
  bool another,
  bool trx_free,
  int *roop_count
) {
  ha_spider *spider;
  SPIDER_IP_PORT_CONN *ip_port_conn = conn->ip_port_conn;
  DBUG_ENTER("spider_free_conn_from_trx");
  spider_conn_clear_queue(conn);
  conn->use_for_active_standby = FALSE;
  conn->error_mode = 1;
    if (
      trx_free ||
      (
        (
          conn->server_lost ||
          spider_param_conn_recycle_mode(trx->thd) != 2
        ) &&
        !conn->opened_handlers
      )
    ) {
      conn->thd = NULL;
      if (another)
      {
        ha_spider *next_spider;
        my_hash_delete(&trx->trx_another_conn_hash, (uchar*) conn);
        spider = (ha_spider*) conn->another_ha_first;
        while (spider)
        {
          next_spider = spider->next;
          spider_free_tmp_dbton_handler(spider);
          spider_free_tmp_dbton_share(spider->share);
          spider_free_tmp_share_alloc(spider->share);
          spider_free(spider_current_trx, spider->share, MYF(0));
          delete spider;
          spider = next_spider;
        }
        conn->another_ha_first = NULL;
        conn->another_ha_last = NULL;
      } else {
        my_hash_delete(&trx->trx_conn_hash, (uchar*) conn);
      }

      if (
        !trx_free &&
        !conn->server_lost &&
        !conn->queued_connect &&
        spider_param_conn_recycle_mode(trx->thd) == 1
      ) {
        /* conn_recycle_mode == 1 */
        *conn->conn_key = '0';
        conn->casual_read_base_conn = NULL;
        if (
          conn->quick_target &&
          spider_db_free_result((ha_spider *) conn->quick_target, FALSE)
        ) {
          spider_free_conn(conn);
        } else {
          pthread_mutex_lock(&spider_conn_mutex);
          uint old_elements = spider_open_connections.array.max_element;
          if (my_hash_insert(&spider_open_connections, (uchar*) conn))
          {
            pthread_mutex_unlock(&spider_conn_mutex);
            spider_free_conn(conn);
          } else {
            if (ip_port_conn)
            { /* exists */
              if (ip_port_conn->waiting_count)
              {
                pthread_mutex_lock(&ip_port_conn->mutex);
                pthread_cond_signal(&ip_port_conn->cond);
                pthread_mutex_unlock(&ip_port_conn->mutex);
              }
            }
            if (spider_open_connections.array.max_element > old_elements)
            {
              spider_alloc_calc_mem(spider_current_trx,
                spider_open_connections,
                (spider_open_connections.array.max_element - old_elements) *
                spider_open_connections.array.size_of_element);
            }
            pthread_mutex_unlock(&spider_conn_mutex);
          }
        }
      } else {
        /* conn_recycle_mode == 0 */
        if (conn->quick_target)
        {
          spider_db_free_result((ha_spider *) conn->quick_target, TRUE);
        }
        spider_free_conn(conn);
      }
    } else if (roop_count)
      (*roop_count)++;
  DBUG_VOID_RETURN;
}

static inline void spider_memcpy_or_null(char **dest, char *alloced,
                                         char *src, uint *dest_len,
                                         uint tgt_len)
{
  *dest_len= tgt_len;
  if (src)
  {
    *dest= alloced;
    memcpy(*dest, src, tgt_len);
  } else
    *dest= NULL;
}

SPIDER_CONN *spider_create_conn(
  SPIDER_SHARE *share,
  ha_spider *spider,
  int link_idx,
  int base_link_idx,
  uint conn_kind,
  int *error_num
) {
  int *need_mon;
  SPIDER_CONN *conn;
  SPIDER_IP_PORT_CONN *ip_port_conn;
  char *tmp_name, *tmp_host, *tmp_username, *tmp_password, *tmp_socket;
  char *tmp_wrapper, *tmp_db, *tmp_ssl_ca, *tmp_ssl_capath, *tmp_ssl_cert;
  char *tmp_ssl_cipher, *tmp_ssl_key, *tmp_default_file, *tmp_default_group;
  char *tmp_dsn, *tmp_filedsn, *tmp_driver;
  DBUG_ENTER("spider_create_conn");

  if (unlikely(!UTC))
  {
    /* UTC time zone for timestamp columns */
    String tz_00_name(STRING_WITH_LEN("+00:00"), &my_charset_bin);
    UTC = my_tz_find(current_thd, &tz_00_name);
  }

    bool tables_on_different_db_are_joinable;
    if (share->sql_dbton_ids[link_idx] != SPIDER_DBTON_SIZE)
    {
      tables_on_different_db_are_joinable =
        spider_dbton[share->sql_dbton_ids[link_idx]].db_util->
          tables_on_different_db_are_joinable();
    } else {
      tables_on_different_db_are_joinable = TRUE;
    }
    if (!(conn = (SPIDER_CONN *)
      spider_bulk_malloc(spider_current_trx,  SPD_MID_CREATE_CONN_1, MYF(MY_WME | MY_ZEROFILL),
        &conn, (uint) (sizeof(*conn)),
        &tmp_name, (uint) (share->conn_keys_lengths[link_idx] + 1),
        &tmp_host, (uint) (share->tgt_hosts_lengths[link_idx] + 1),
        &tmp_username,
          (uint) (share->tgt_usernames_lengths[link_idx] + 1),
        &tmp_password,
          (uint) (share->tgt_passwords_lengths[link_idx] + 1),
        &tmp_socket, (uint) (share->tgt_sockets_lengths[link_idx] + 1),
        &tmp_wrapper,
          (uint) (share->tgt_wrappers_lengths[link_idx] + 1),
        &tmp_db, (uint) (tables_on_different_db_are_joinable ?
          0 : share->tgt_dbs_lengths[link_idx] + 1),
        &tmp_ssl_ca, (uint) (share->tgt_ssl_cas_lengths[link_idx] + 1),
        &tmp_ssl_capath,
          (uint) (share->tgt_ssl_capaths_lengths[link_idx] + 1),
        &tmp_ssl_cert,
          (uint) (share->tgt_ssl_certs_lengths[link_idx] + 1),
        &tmp_ssl_cipher,
          (uint) (share->tgt_ssl_ciphers_lengths[link_idx] + 1),
        &tmp_ssl_key,
          (uint) (share->tgt_ssl_keys_lengths[link_idx] + 1),
        &tmp_default_file,
          (uint) (share->tgt_default_files_lengths[link_idx] + 1),
        &tmp_default_group,
          (uint) (share->tgt_default_groups_lengths[link_idx] + 1),
        &tmp_dsn,
          (uint) (share->tgt_dsns_lengths[link_idx] + 1),
        &tmp_filedsn,
          (uint) (share->tgt_filedsns_lengths[link_idx] + 1),
        &tmp_driver,
          (uint) (share->tgt_drivers_lengths[link_idx] + 1),
        &need_mon, (uint) (sizeof(int)),
        NullS))
    ) {
      *error_num = HA_ERR_OUT_OF_MEM;
      goto error_alloc_conn;
    }

    conn->default_database.init_calc_mem(SPD_MID_CREATE_CONN_2);
    conn->conn_key_length = share->conn_keys_lengths[link_idx];
    conn->conn_key = tmp_name;
    memcpy(conn->conn_key, share->conn_keys[link_idx],
      share->conn_keys_lengths[link_idx]);
    conn->conn_key_hash_value = share->conn_keys_hash_value[link_idx];
    spider_memcpy_or_null(&conn->tgt_host, tmp_host,
                          share->tgt_hosts[link_idx], &conn->tgt_host_length,
                          share->tgt_hosts_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_username, tmp_username,
                          share->tgt_usernames[link_idx],
                          &conn->tgt_username_length,
                          share->tgt_usernames_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_password, tmp_password,
                          share->tgt_passwords[link_idx],
                          &conn->tgt_password_length,
                          share->tgt_passwords_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_socket, tmp_socket,
                          share->tgt_sockets[link_idx],
                          &conn->tgt_socket_length,
                          share->tgt_sockets_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_wrapper, tmp_wrapper,
                          share->tgt_wrappers[link_idx],
                          &conn->tgt_wrapper_length,
                          share->tgt_wrappers_lengths[link_idx]);
    if (!tables_on_different_db_are_joinable)
    {
      spider_memcpy_or_null(&conn->tgt_db, tmp_db, share->tgt_dbs[link_idx],
                            &conn->tgt_db_length,
                            share->tgt_dbs_lengths[link_idx]);
    }
    spider_memcpy_or_null(&conn->tgt_ssl_ca, tmp_ssl_ca,
                          share->tgt_ssl_cas[link_idx],
                          &conn->tgt_ssl_ca_length,
                          share->tgt_ssl_cas_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_ssl_capath, tmp_ssl_capath,
                          share->tgt_ssl_capaths[link_idx],
                          &conn->tgt_ssl_capath_length,
                          share->tgt_ssl_capaths_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_ssl_cert, tmp_ssl_cert,
                          share->tgt_ssl_certs[link_idx],
                          &conn->tgt_ssl_cert_length,
                          share->tgt_ssl_certs_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_ssl_cipher, tmp_ssl_cipher,
                          share->tgt_ssl_ciphers[link_idx],
                          &conn->tgt_ssl_cipher_length,
                          share->tgt_ssl_ciphers_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_ssl_key, tmp_ssl_key,
                          share->tgt_ssl_keys[link_idx],
                          &conn->tgt_ssl_key_length,
                          share->tgt_ssl_keys_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_default_file, tmp_default_file,
                          share->tgt_default_files[link_idx],
                          &conn->tgt_default_file_length,
                          share->tgt_default_files_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_default_group, tmp_default_group,
                          share->tgt_default_groups[link_idx],
                          &conn->tgt_default_group_length,
                          share->tgt_default_groups_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_dsn, tmp_dsn, share->tgt_dsns[link_idx],
                          &conn->tgt_dsn_length,
                          share->tgt_dsns_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_filedsn, tmp_filedsn, share->tgt_filedsns[link_idx],
                          &conn->tgt_filedsn_length,
                          share->tgt_filedsns_lengths[link_idx]);
    spider_memcpy_or_null(&conn->tgt_driver, tmp_driver, share->tgt_drivers[link_idx],
                          &conn->tgt_driver_length,
                          share->tgt_drivers_lengths[link_idx]);
    conn->tgt_port = share->tgt_ports[link_idx];
    conn->tgt_ssl_vsc = share->tgt_ssl_vscs[link_idx];
    conn->dbton_id = share->sql_dbton_ids[link_idx];
  if (conn->dbton_id == SPIDER_DBTON_SIZE)
  {
      my_printf_error(
        ER_SPIDER_SQL_WRAPPER_IS_INVALID_NUM,
        ER_SPIDER_SQL_WRAPPER_IS_INVALID_STR,
        MYF(0), conn->tgt_wrapper);
      *error_num = ER_SPIDER_SQL_WRAPPER_IS_INVALID_NUM;
    goto error_invalid_wrapper;
  }
  if (!(conn->db_conn = spider_dbton[conn->dbton_id].create_db_conn(conn)))
  {
    *error_num = HA_ERR_OUT_OF_MEM;
    goto error_db_conn_create;
  }
  if ((*error_num = conn->db_conn->init()))
  {
    goto error_db_conn_init;
  }
  conn->join_trx = 0;
  conn->thd = NULL;
  conn->table_lock = 0;
  conn->semi_trx_isolation = -2;
  conn->semi_trx_isolation_chk = FALSE;
  conn->semi_trx_chk = FALSE;
  conn->link_idx = base_link_idx;
  conn->conn_kind = conn_kind;
  conn->conn_need_mon = need_mon;
  if (spider)
    conn->need_mon = &spider->need_mons[base_link_idx];
  else
    conn->need_mon = need_mon;

  if (mysql_mutex_init(spd_key_mutex_mta_conn, &conn->mta_conn_mutex,
    MY_MUTEX_INIT_FAST))
  {
    *error_num = HA_ERR_OUT_OF_MEM;
    goto error_mta_conn_mutex_init;
  }

  if (unlikely((*error_num = spider_conn_init(conn))))
  {
    goto error_conn_init;
  }

  spider_conn_queue_connect(share, conn, link_idx);
  conn->ping_time = (time_t) time((time_t*) 0);
  conn->connect_error_time = conn->ping_time;
  pthread_mutex_lock(&spider_conn_id_mutex);
  conn->conn_id = spider_conn_id;
  ++spider_conn_id;
  pthread_mutex_unlock(&spider_conn_id_mutex);

  pthread_mutex_lock(&spider_ipport_conn_mutex);
  if ((ip_port_conn = (SPIDER_IP_PORT_CONN*) my_hash_search_using_hash_value(
    &spider_ipport_conns, conn->conn_key_hash_value,
    (uchar*)conn->conn_key, conn->conn_key_length)))
  { /* exists, +1 */
    pthread_mutex_unlock(&spider_ipport_conn_mutex);
    pthread_mutex_lock(&ip_port_conn->mutex);
    if (spider_param_max_connections())
    { /* enable conncetion pool */
      if (ip_port_conn->ip_port_count >= spider_param_max_connections())
      { /* bigger than the max num of connections, free conn and return NULL */
        pthread_mutex_unlock(&ip_port_conn->mutex);
        *error_num = ER_SPIDER_CON_COUNT_ERROR;
        goto error_too_many_ipport_count;
      }
    }
    ip_port_conn->ip_port_count++;
    pthread_mutex_unlock(&ip_port_conn->mutex);
  }
  else
  {// do not exist
    ip_port_conn = spider_create_ipport_conn(conn);
    if (!ip_port_conn) {
      /* failed, always do not effect 'create conn' */
      pthread_mutex_unlock(&spider_ipport_conn_mutex);
      DBUG_RETURN(conn);
    }
    if (my_hash_insert(&spider_ipport_conns, (uchar *)ip_port_conn)) {
      /* insert failed, always do not effect 'create conn' */
      pthread_mutex_unlock(&spider_ipport_conn_mutex);
      DBUG_RETURN(conn);
    }
    pthread_mutex_unlock(&spider_ipport_conn_mutex);
  }
  conn->ip_port_conn = ip_port_conn;

  DBUG_RETURN(conn);

error_too_many_ipport_count:
  spider_conn_done(conn);
error_conn_init:
  pthread_mutex_destroy(&conn->mta_conn_mutex);
error_mta_conn_mutex_init:
error_db_conn_init:
  delete conn->db_conn;
error_db_conn_create:
error_invalid_wrapper:
  spider_free(spider_current_trx, conn, MYF(0));
error_alloc_conn:
  DBUG_RETURN(NULL);
}

SPIDER_CONN *spider_get_conn(
  SPIDER_SHARE *share,
  int link_idx,
  char *conn_key,
  SPIDER_TRX *trx,
  ha_spider *spider,
  bool another,
  bool thd_chg,
  uint conn_kind,
  int *error_num
) {
  SPIDER_CONN *conn = NULL;
  int base_link_idx = link_idx;
  DBUG_ENTER("spider_get_conn");
  DBUG_PRINT("info",("spider conn_kind=%u", conn_kind));

  if (spider)
    link_idx = spider->conn_link_idx[base_link_idx];
  DBUG_PRINT("info",("spider link_idx=%u", link_idx));
  DBUG_PRINT("info",("spider base_link_idx=%u", base_link_idx));

#ifdef DBUG_TRACE
    spider_print_keys(conn_key, share->conn_keys_lengths[link_idx]);
#endif
  if (
        (another &&
          !(conn = (SPIDER_CONN*) my_hash_search_using_hash_value(
            &trx->trx_another_conn_hash,
            share->conn_keys_hash_value[link_idx],
            (uchar*) conn_key, share->conn_keys_lengths[link_idx]))) ||
        (!another &&
          !(conn = (SPIDER_CONN*) my_hash_search_using_hash_value(
            &trx->trx_conn_hash,
            share->conn_keys_hash_value[link_idx],
            (uchar*) conn_key, share->conn_keys_lengths[link_idx])))
  )
  {
    if (
      !trx->thd ||
        (
          (spider_param_conn_recycle_mode(trx->thd) & 1) ||
          spider_param_conn_recycle_strict(trx->thd)
        )
    ) {
        pthread_mutex_lock(&spider_conn_mutex);
        if (!(conn = (SPIDER_CONN*) my_hash_search_using_hash_value(
          &spider_open_connections, share->conn_keys_hash_value[link_idx],
          (uchar*) share->conn_keys[link_idx],
          share->conn_keys_lengths[link_idx])))
        {
          pthread_mutex_unlock(&spider_conn_mutex);
          if (spider_param_max_connections())
          { /* enable connection pool */
            conn = spider_get_conn_from_idle_connection(share, link_idx, conn_key, spider, conn_kind, base_link_idx, error_num);
            /* failed get conn, goto error */
            if (!conn)
              goto error;

          }
          else
          { /* did not enable conncetion pool , create_conn */
            DBUG_PRINT("info",("spider create new conn"));
            if (!(conn = spider_create_conn(share, spider, link_idx,
              base_link_idx, conn_kind, error_num)))
              goto error;
            *conn->conn_key = *conn_key;
            if (spider)
            {
              spider->conns[base_link_idx] = conn;
              if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
                conn->use_for_active_standby = TRUE;
            }
          }
        } else {
          my_hash_delete(&spider_open_connections, (uchar*) conn);
          pthread_mutex_unlock(&spider_conn_mutex);
          DBUG_PRINT("info",("spider get global conn"));
          if (spider)
          {
            spider->conns[base_link_idx] = conn;
            if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
              conn->use_for_active_standby = TRUE;
          }
        }
    } else {
      DBUG_PRINT("info",("spider create new conn"));
      /* conn_recycle_strict = 0 and conn_recycle_mode = 0 or 2 */
      if (!(conn = spider_create_conn(share, spider, link_idx, base_link_idx,
        conn_kind, error_num)))
        goto error;
      *conn->conn_key = *conn_key;
      if (spider)
      {
          spider->conns[base_link_idx] = conn;
        if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
          conn->use_for_active_standby = TRUE;
      }
    }
    conn->thd = trx->thd;
    conn->priority = share->priority;

      if (another)
      {
        uint old_elements = trx->trx_another_conn_hash.array.max_element;
        if (my_hash_insert(&trx->trx_another_conn_hash, (uchar*) conn))
        {
          spider_free_conn(conn);
          *error_num = HA_ERR_OUT_OF_MEM;
          goto error;
        }
        if (trx->trx_another_conn_hash.array.max_element > old_elements)
        {
          spider_alloc_calc_mem(spider_current_trx,
            trx->trx_another_conn_hash,
            (trx->trx_another_conn_hash.array.max_element - old_elements) *
            trx->trx_another_conn_hash.array.size_of_element);
        }
      } else {
        uint old_elements = trx->trx_conn_hash.array.max_element;
        if (my_hash_insert(&trx->trx_conn_hash, (uchar*) conn))
        {
          spider_free_conn(conn);
          *error_num = HA_ERR_OUT_OF_MEM;
          goto error;
        }
        if (trx->trx_conn_hash.array.max_element > old_elements)
        {
          spider_alloc_calc_mem(spider_current_trx,
            trx->trx_conn_hash,
            (trx->trx_conn_hash.array.max_element - old_elements) *
            trx->trx_conn_hash.array.size_of_element);
        }
      }
  } else if (spider)
  {
      spider->conns[base_link_idx] = conn;
    if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
      conn->use_for_active_standby = TRUE;
  }
  conn->link_idx = base_link_idx;

  if (conn->queued_connect)
    spider_conn_queue_connect_rewrite(share, conn, link_idx);

  if (conn->queued_ping)
  {
    if (spider)
      spider_conn_queue_ping_rewrite(spider, conn, base_link_idx);
    else
      conn->queued_ping = FALSE;
  }

    if (unlikely(spider && spider->wide_handler->top_share &&
      (*error_num = spider_conn_queue_loop_check(
        conn, spider, base_link_idx))))
    {
      goto error;
    }

  DBUG_PRINT("info",("spider conn=%p", conn));
  DBUG_RETURN(conn);

error:
  DBUG_RETURN(NULL);
}

int spider_free_conn(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_free_conn");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  SPIDER_IP_PORT_CONN* ip_port_conn = conn->ip_port_conn;
  if (ip_port_conn)
  { /* free conn, ip_port_count-- */
    pthread_mutex_lock(&ip_port_conn->mutex);
    if (ip_port_conn->ip_port_count > 0)
      ip_port_conn->ip_port_count--;
    pthread_mutex_unlock(&ip_port_conn->mutex);
  }
  if (conn->conn_holder_for_direct_join)
    conn->conn_holder_for_direct_join->conn= NULL;
  spider_free_conn_alloc(conn);
  spider_free(spider_current_trx, conn, MYF(0));
  DBUG_RETURN(0);
}

/**
  May get or create a connection spawning a background thread

  For each link (data node, formally representable as the tuple
  (spider, link_idx)), there is an associated casual read value
  (`spider->result_list.casual_read[link_idx]').

  If the CRV is 0, do nothing. Otherwise, An casual read id
  (`conn->casual_read_current_id`) is associated with the link and
  query id. The CRI starts from 2, and is used only when CRV is 1, to
  update the CRV (see below). The updated CRV is then used to
  construct the connection key used for get or create a connection
  that spawns a background thread to execute queries.

  If the CRV is 1, it is assigned CRI. The latter is then incremented
  by 1. The CRI will only go up to 63, before "wrapping" back to 2.

  If 2 <= CRV <= 63, it is left alone.

  Note that this function relies on the assumption that the CRV is
  reset (e.g. using `spider_param_casual_read()') between consecutive
  calls of this function for the CRV == 1 case to auto-increment as
  expected.
*/
int spider_check_and_get_casual_read_conn(
  THD *thd,
  ha_spider *spider,
  int link_idx
) {
  int error_num;
  DBUG_ENTER("spider_check_and_get_casual_read_conn");
  if (!spider->result_list.casual_read[link_idx])
    DBUG_RETURN(0);
  SPIDER_CONN *conn = spider->conns[link_idx];
  if (conn->casual_read_query_id != thd->query_id)
  {
    conn->casual_read_query_id = thd->query_id;
    conn->casual_read_current_id = 2;
  }
  if (spider->result_list.casual_read[link_idx] == 1)
  {
    spider->result_list.casual_read[link_idx] = conn->casual_read_current_id;
    ++conn->casual_read_current_id;
    if (conn->casual_read_current_id > 63)
      conn->casual_read_current_id = 2;
  }
  char first_byte_bak = *spider->conn_keys[link_idx];
  *spider->conn_keys[link_idx] =
    '0' + spider->result_list.casual_read[link_idx];
  if (!(spider->conns[link_idx]= spider_get_conn(
          spider->share, link_idx, spider->conn_keys[link_idx],
          spider->wide_handler->trx, spider, FALSE, TRUE,
          SPIDER_CONN_KIND_MYSQL, &error_num)))
  {
    *spider->conn_keys[link_idx] = first_byte_bak;
    DBUG_RETURN(error_num);
  }
  *spider->conn_keys[link_idx] = first_byte_bak;
  spider->conns[link_idx]->casual_read_base_conn = conn;
  spider_check_and_set_autocommit(thd, spider->conns[link_idx], NULL);
  DBUG_RETURN(0);
}

int spider_check_and_init_casual_read(
  THD *thd,
  ha_spider *spider,
  int link_idx
) {
  int error_num;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  SPIDER_SHARE *share = spider->share;
  DBUG_ENTER("spider_check_and_init_casual_read");
  if (
    spider_param_sync_autocommit(thd) &&
    (!thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) &&
    (
      result_list->direct_order_limit
      || result_list->direct_aggregate
    )
  ) {
    if (!result_list->casual_read[link_idx])
    {
      result_list->casual_read[link_idx] =
        spider_param_casual_read(thd, share->casual_read);
    }
    if ((error_num = spider_check_and_get_casual_read_conn(thd, spider,
      link_idx)))
    {
      DBUG_RETURN(error_num);
    }
    SPIDER_CONN *conn = spider->conns[link_idx];
    if (
      conn->casual_read_base_conn &&
      (error_num = spider_create_conn_thread(conn))
    ) {
      DBUG_RETURN(error_num);
    }
  }
  DBUG_RETURN(0);
}

void spider_conn_queue_connect(
  SPIDER_SHARE *share,
  SPIDER_CONN *conn,
  int link_idx
) {
  DBUG_ENTER("spider_conn_queue_connect");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_connect = TRUE;
/*
  conn->queued_connect_share = share;
  conn->queued_connect_link_idx = link_idx;
*/
  DBUG_VOID_RETURN;
}

void spider_conn_queue_connect_rewrite(
  SPIDER_SHARE *share,
  SPIDER_CONN *conn,
  int link_idx
) {
  DBUG_ENTER("spider_conn_queue_connect_rewrite");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_connect_share = share;
  conn->queued_connect_link_idx = link_idx;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_ping(
  ha_spider *spider,
  SPIDER_CONN *conn,
  int link_idx
) {
  DBUG_ENTER("spider_conn_queue_ping");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_ping = TRUE;
  conn->queued_ping_spider = spider;
  conn->queued_ping_link_idx = link_idx;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_ping_rewrite(
  ha_spider *spider,
  SPIDER_CONN *conn,
  int link_idx
) {
  DBUG_ENTER("spider_conn_queue_ping_rewrite");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_ping_spider = spider;
  conn->queued_ping_link_idx = link_idx;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_trx_isolation(
  SPIDER_CONN *conn,
  int trx_isolation
) {
  DBUG_ENTER("spider_conn_queue_trx_isolation");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_trx_isolation = TRUE;
  conn->queued_trx_isolation_val = trx_isolation;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_semi_trx_isolation(
  SPIDER_CONN *conn,
  int trx_isolation
) {
  DBUG_ENTER("spider_conn_queue_semi_trx_isolation");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_semi_trx_isolation = TRUE;
  conn->queued_semi_trx_isolation_val = trx_isolation;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_autocommit(
  SPIDER_CONN *conn,
  bool autocommit
) {
  DBUG_ENTER("spider_conn_queue_autocommit");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_autocommit = TRUE;
  conn->queued_autocommit_val = autocommit;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_sql_log_off(
  SPIDER_CONN *conn,
  bool sql_log_off
) {
  DBUG_ENTER("spider_conn_queue_sql_log_off");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_sql_log_off = TRUE;
  conn->queued_sql_log_off_val = sql_log_off;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_wait_timeout(
  SPIDER_CONN *conn,
  int wait_timeout
) {
  DBUG_ENTER("spider_conn_queue_wait_timeout");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  if (wait_timeout > 0)
  {
    conn->queued_wait_timeout = TRUE;
    conn->queued_wait_timeout_val = wait_timeout;
  }
  DBUG_VOID_RETURN;
}

void spider_conn_queue_sql_mode(
  SPIDER_CONN *conn,
  sql_mode_t sql_mode
) {
  DBUG_ENTER("spider_conn_queue_sql_mode");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  DBUG_ASSERT(!(sql_mode & ~full_sql_mode));
  conn->queued_sql_mode = TRUE;
  conn->queued_sql_mode_val = (sql_mode & pushdown_sql_mode);
  DBUG_VOID_RETURN;
}

void spider_conn_queue_time_zone(
  SPIDER_CONN *conn,
  Time_zone *time_zone
) {
  DBUG_ENTER("spider_conn_queue_time_zone");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_time_zone = TRUE;
  conn->queued_time_zone_val = time_zone;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_UTC_time_zone(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_conn_queue_UTC_time_zone");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  spider_conn_queue_time_zone(conn, UTC);
  DBUG_VOID_RETURN;
}

/*
  Construct merged values and insert into the loop check queue

  Search the loop_check_queue for the data node table, and if one does
  not exist, construct the merged value in the same format as the
  right hand side. Otherwise, merge the right hand side of the
  existing SPIDER_CONN_LOOP_CHECK with the right hand side of lcptr
  into one right hand side. In either case, add the
  SPIDER_CONN_LOOP_CHECK to the loop check queue
*/
int spider_conn_queue_and_merge_loop_check(
  SPIDER_CONN *conn,
  SPIDER_CONN_LOOP_CHECK *lcptr
) {
  int error_num = HA_ERR_OUT_OF_MEM;
  char *tmp_name, *cur_name, *to_name, *full_name, *from_value,
    *merged_value;
  SPIDER_CONN_LOOP_CHECK *lcqptr, *lcrptr;
  DBUG_ENTER("spider_conn_queue_and_merge_loop_check");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  if (!(lcqptr = (SPIDER_CONN_LOOP_CHECK *)
    my_hash_search_using_hash_value(&conn->loop_check_queue,
    lcptr->hash_value_to,
    (uchar *) lcptr->to_name.str, lcptr->to_name.length)))
  {
    /*
      Construct the right hand side:
      -<mac>-<pid>-<cur_table>-<from_value>
    */
    DBUG_PRINT("info", ("spider create merged_value and insert"));
    lcptr->merged_value.length = spider_unique_id.length +
      lcptr->cur_name.length + lcptr->from_value.length + 1;
    tmp_name = (char *) lcptr->merged_value.str;
    memcpy(tmp_name, spider_unique_id.str, spider_unique_id.length);
    tmp_name += spider_unique_id.length;
    memcpy(tmp_name, lcptr->cur_name.str, lcptr->cur_name.length);
    tmp_name += lcptr->cur_name.length;
    *tmp_name = '-';
    ++tmp_name;
    memcpy(tmp_name, lcptr->from_value.str, lcptr->from_value.length + 1);
    if (unlikely(my_hash_insert(&conn->loop_check_queue, (uchar *) lcptr)))
    {
      goto error_hash_insert_queue;
    }
    lcptr->flag |= SPIDER_LOP_CHK_QUEUED;
  } else {
    /* Merge lcptr and lcqptr into a newly created lcrptr. */
    DBUG_PRINT("info", ("spider append merged_value and replace"));
    if (unlikely(!spider_bulk_malloc(spider_current_trx, SPD_MID_CONN_QUEUE_AND_MERGE_LOOP_CHECK_1, MYF(MY_WME),
      &lcrptr, (uint) (sizeof(SPIDER_CONN_LOOP_CHECK)),
      &cur_name, (uint) (lcqptr->cur_name.length + 1),
      &to_name, (uint) (lcqptr->to_name.length + 1),
      &full_name, (uint) (lcqptr->full_name.length + 1),
      &from_value, (uint) (lcqptr->from_value.length + 1),
      &merged_value, (uint) (lcqptr->merged_value.length +
        spider_unique_id.length + lcptr->cur_name.length +
        lcptr->from_value.length + 2),
      NullS)
    )) {
      goto error_alloc_loop_check_replace;
    }
    /*
      TODO: the new lcrptr has the same cur_name, to_name, full_name
      and from_value as lcqptr, but they do not seem to be relevant.
    */
    lcrptr->hash_value_to = lcqptr->hash_value_to;
    lcrptr->cur_name.str = cur_name;
    lcrptr->cur_name.length = lcqptr->cur_name.length;
    memcpy(cur_name, lcqptr->cur_name.str, lcqptr->cur_name.length + 1);
    lcrptr->to_name.str = to_name;
    lcrptr->to_name.length = lcqptr->to_name.length;
    memcpy(to_name, lcqptr->to_name.str, lcqptr->to_name.length + 1);
    lcrptr->full_name.str = full_name;
    lcrptr->full_name.length = lcqptr->full_name.length;
    memcpy(full_name, lcqptr->full_name.str, lcqptr->full_name.length + 1);
    lcrptr->from_value.str = from_value;
    lcrptr->from_value.length = lcqptr->from_value.length;
    memcpy(from_value, lcqptr->from_value.str, lcqptr->from_value.length + 1);
    /*
      The merged_value of lcrptr is a concatenation of that of lcqptr
      and constructed merged_value from lcptr.
    */
    lcrptr->merged_value.str = merged_value;
    lcrptr->merged_value.length =
      lcqptr->merged_value.length + spider_unique_id.length +
      lcptr->cur_name.length + 1 + lcptr->from_value.length;
    memcpy(merged_value,
      lcqptr->merged_value.str, lcqptr->merged_value.length);
    merged_value += lcqptr->merged_value.length;
    memcpy(merged_value, spider_unique_id.str, spider_unique_id.length);
    merged_value += spider_unique_id.length;
    memcpy(merged_value, lcptr->cur_name.str, lcptr->cur_name.length);
    merged_value += lcptr->cur_name.length;
    *merged_value = '-';
    ++merged_value;
    memcpy(merged_value, lcptr->from_value.str, lcptr->from_value.length + 1);

    DBUG_PRINT("info", ("spider free lcqptr"));
    my_hash_delete(&conn->loop_checked, (uchar*) lcqptr);
    my_hash_delete(&conn->loop_check_queue, (uchar*) lcqptr);
    spider_free(spider_current_trx, lcqptr, MYF(0));

    lcptr = lcrptr;
    if (unlikely(my_hash_insert(&conn->loop_checked, (uchar *) lcptr)))
    {
      goto error_hash_insert;
    }
    if (unlikely(my_hash_insert(&conn->loop_check_queue, (uchar *) lcptr)))
    {
      goto error_hash_insert_queue;
    }
    lcptr->flag = SPIDER_LOP_CHK_MERAGED;
  }
  DBUG_RETURN(0);

error_alloc_loop_check_replace:
error_hash_insert_queue:
  my_hash_delete(&conn->loop_checked, (uchar*) lcptr);
error_hash_insert:
  spider_free(spider_current_trx, lcptr, MYF(0));
  pthread_mutex_unlock(&conn->loop_check_mutex);
  DBUG_RETURN(error_num);
}

int spider_conn_reset_queue_loop_check(
  SPIDER_CONN *conn
) {
  SPIDER_CONN_LOOP_CHECK *lcptr;
  DBUG_ENTER("spider_conn_reset_queue_loop_check");
  uint l = 0;
  pthread_mutex_lock(&conn->loop_check_mutex);
  while ((lcptr = (SPIDER_CONN_LOOP_CHECK *) my_hash_element(
    &conn->loop_checked, l)))
  {
    if (!lcptr->flag)
    {
      DBUG_PRINT("info", ("spider free lcptr"));
      my_hash_delete(&conn->loop_checked, (uchar*) lcptr);
      spider_free(spider_current_trx, lcptr, MYF(0));
    }
    ++l;
  }

  pthread_mutex_unlock(&conn->loop_check_mutex);
  DBUG_RETURN(0);
}

int spider_conn_queue_loop_check(
  SPIDER_CONN *conn,
  ha_spider *spider,
  int link_idx
) {
  int error_num = HA_ERR_OUT_OF_MEM;
  uint conn_link_idx = spider->conn_link_idx[link_idx], buf_sz;
  char path[FN_REFLEN + 1];
  char *tmp_name, *cur_name, *to_name, *full_name, *from_value,
    *merged_value;
  user_var_entry *loop_check;
  char *loop_check_buf;
  THD *thd = spider->wide_handler->trx->thd;
  TABLE_SHARE *top_share = spider->wide_handler->top_share;
  SPIDER_SHARE *share = spider->share;
  SPIDER_CONN_LOOP_CHECK *lcptr;
  LEX_CSTRING lex_str, from_str, to_str;
  DBUG_ENTER("spider_conn_queue_loop_check");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  /*
    construct loop check user var name (left hand side) into
    lex_str. It is of the format

    spider_lc_<spider_table_name>

    So if the spider table name is ./test/t1, then the constructed
    user var name is:

    spider_lc_./test/t1
  */
  lex_str.length = top_share->path.length + SPIDER_SQL_LOP_CHK_PRM_PRF_LEN;
  buf_sz = lex_str.length + 2;
  loop_check_buf = (char *) my_alloca(buf_sz);
  if (unlikely(!loop_check_buf))
  {
    DBUG_RETURN(HA_ERR_OUT_OF_MEM);
  }
  lex_str.str = loop_check_buf;
  memcpy(loop_check_buf,
    SPIDER_SQL_LOP_CHK_PRM_PRF_STR, SPIDER_SQL_LOP_CHK_PRM_PRF_LEN);
  memcpy(loop_check_buf + SPIDER_SQL_LOP_CHK_PRM_PRF_LEN,
    top_share->path.str, top_share->path.length);
  loop_check_buf[lex_str.length] = '\0';
  DBUG_PRINT("info", ("spider param name=%s", lex_str.str));
  loop_check = get_variable(&thd->user_vars, &lex_str, FALSE);
  if (!loop_check || loop_check->type_handler()->result_type() != STRING_RESULT)
  {
    DBUG_PRINT("info", ("spider client is not Spider"));
    lex_str.str = "";
    lex_str.length = 0;
    from_str.str = "";
    from_str.length = 0;
  } else {
    lex_str.str = loop_check->value;
    lex_str.length = loop_check->length;
    /*
      Validate that there are at least four dashes in the user var
      value: -<mac_addr>-<proc_id>-<table_name>-

      Note: if the value is merged from multiple values, such as

      "-<mac1>-<pid1>-<table_name1>--<mac2>-<pid2>-<table_name2>--<mac3>-<pid3>-<table_name3>-"

      then only the first component is put into from_str
    */
    DBUG_PRINT("info", ("spider from_str=%s", lex_str.str));
    if (unlikely(!(tmp_name = strchr(loop_check->value, '-'))))
    {
      DBUG_PRINT("info", ("spider invalid value for loop checking 1"));
      from_str.str = "";
      from_str.length = 0;
    }
    else if (unlikely(!(tmp_name = strchr(tmp_name + 1, '-'))))
    {
      DBUG_PRINT("info", ("spider invalid value for loop checking 2"));
      from_str.str = "";
      from_str.length = 0;
    }
    else if (unlikely(!(tmp_name = strchr(tmp_name + 1, '-'))))
    {
      DBUG_PRINT("info", ("spider invalid value for loop checking 3"));
      from_str.str = "";
      from_str.length = 0;
    }
    else if (unlikely(!(tmp_name = strchr(tmp_name + 1, '-'))))
    {
      DBUG_PRINT("info", ("spider invalid value for loop checking 4"));
      from_str.str = "";
      from_str.length = 0;
    }
    else
    {
      /*
        Validation passed. Put the first component of rhs in from_str
      */
      from_str.str = lex_str.str;
      from_str.length = tmp_name - lex_str.str + 1;
    }
  }
  my_afree(loop_check_buf);
  /*
    construct loop_check_buf as <from_str>-<cur>-<to_str> e.g.
    "-<mac>-<pid>-./test/t0--./test/t1-./test/t2", later used as
    full_name

    from_str is the first component in the user var value (RHS) or
    empty if user var value is empty, cur is the spider table, to_str
    is the remote data node table
  */
  to_str.length = build_table_filename(path, FN_REFLEN,
    share->tgt_dbs[conn_link_idx] ? share->tgt_dbs[conn_link_idx] : "",
    share->tgt_table_names[conn_link_idx], "", 0);
  to_str.str = path;
  DBUG_PRINT("info", ("spider to=%s", to_str.str));
  buf_sz = from_str.length + top_share->path.length + to_str.length + 3;
  loop_check_buf = (char *) my_alloca(buf_sz);
  if (unlikely(!loop_check_buf))
  {
    DBUG_RETURN(HA_ERR_OUT_OF_MEM);
  }
  DBUG_PRINT("info", ("spider top_share->path=%s", top_share->path.str));
  memcpy(loop_check_buf, from_str.str, from_str.length);
  tmp_name = loop_check_buf + from_str.length;
  *tmp_name = '-';
  ++tmp_name;
  memcpy(tmp_name, top_share->path.str, top_share->path.length);
  tmp_name += top_share->path.length;
  *tmp_name = '-';
  ++tmp_name;
  memcpy(tmp_name, to_str.str, to_str.length);
  tmp_name += to_str.length;
  *tmp_name = '\0';
  my_hash_value_type hash_value = my_calc_hash(&conn->loop_checked,
    (uchar *) loop_check_buf, buf_sz - 1);
  pthread_mutex_lock(&conn->loop_check_mutex);
  lcptr = (SPIDER_CONN_LOOP_CHECK *)
    my_hash_search_using_hash_value(&conn->loop_checked, hash_value,
    (uchar *) loop_check_buf, buf_sz - 1);
  if (
    !lcptr ||
    (
      !lcptr->flag &&
      (
        lcptr->from_value.length != lex_str.length ||
        memcmp(lcptr->from_value.str, lex_str.str, lex_str.length)
      )
    )
  )
  {
    if (unlikely(lcptr))
    {
      DBUG_PRINT("info", ("spider free lcptr"));
      my_hash_delete(&conn->loop_checked, (uchar*) lcptr);
      spider_free(spider_current_trx, lcptr, MYF(0));
    }
    DBUG_PRINT("info", ("spider alloc_lcptr"));
    if (unlikely(!spider_bulk_malloc(spider_current_trx, SPD_MID_CONN_QUEUE_LOOP_CHECK_1, MYF(MY_WME),
      &lcptr, (uint) (sizeof(SPIDER_CONN_LOOP_CHECK)),
      &cur_name, (uint) (top_share->path.length + 1),
      &to_name, (uint) (to_str.length + 1),
      &full_name, (uint) (buf_sz),
      &from_value, (uint) (lex_str.length + 1),
      &merged_value, (uint) (spider_unique_id.length + top_share->path.length +
        lex_str.length + 2),
      NullS)
    )) {
      my_afree(loop_check_buf);
      goto error_alloc_loop_check;
    }
    lcptr->flag = 0;
    lcptr->cur_name.str = cur_name;
    lcptr->cur_name.length = top_share->path.length;
    memcpy(cur_name, top_share->path.str, top_share->path.length + 1);
    lcptr->to_name.str = to_name;
    lcptr->to_name.length = to_str.length;
    memcpy(to_name, to_str.str, to_str.length + 1);
    lcptr->full_name.str = full_name;
    lcptr->full_name.length = buf_sz - 1;
    memcpy(full_name, loop_check_buf, buf_sz);
    lcptr->from_value.str = from_value;
    lcptr->from_value.length = lex_str.length;
    memcpy(from_value, lex_str.str, lex_str.length + 1);
    /*
      merged_value will only be populated later, in
      spider_conn_queue_and_merge_loop_check()
    */
    lcptr->merged_value.str = merged_value;
    lcptr->hash_value_to = my_calc_hash(&conn->loop_check_queue,
      (uchar *) to_str.str, to_str.length);
    /*
      Mark as checked. It will be added to loop_check_queue in
      spider_conn_queue_and_merge_loop_check() below for checking
    */
    if (unlikely(my_hash_insert(&conn->loop_checked, (uchar *) lcptr)))
    {
      my_afree(loop_check_buf);
      goto error_hash_insert;
    }
  } else {
    /* Already marked as checked, ignore and return. */
    if (!lcptr->flag)
    {
      DBUG_PRINT("info", ("spider add to ignored list"));
      lcptr->flag |= SPIDER_LOP_CHK_IGNORED;
    }
    pthread_mutex_unlock(&conn->loop_check_mutex);
    my_afree(loop_check_buf);
    DBUG_PRINT("info", ("spider be sent or queued already"));
    DBUG_RETURN(0);
  }
  my_afree(loop_check_buf);

  if ((error_num = spider_conn_queue_and_merge_loop_check(conn, lcptr)))
  {
    goto error_queue_and_merge;
  }
  pthread_mutex_unlock(&conn->loop_check_mutex);
  DBUG_RETURN(0);

error_hash_insert:
  spider_free(spider_current_trx, lcptr, MYF(0));
error_queue_and_merge:
  pthread_mutex_unlock(&conn->loop_check_mutex);
error_alloc_loop_check:
  DBUG_RETURN(error_num);
}

void spider_conn_queue_start_transaction(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_conn_queue_start_transaction");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  DBUG_ASSERT(!conn->trx_start);
  conn->queued_trx_start = TRUE;
  conn->trx_start = TRUE;
  DBUG_VOID_RETURN;
}

void spider_conn_queue_xa_start(
  SPIDER_CONN *conn,
  XID *xid
) {
  DBUG_ENTER("spider_conn_queue_xa_start");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_xa_start = TRUE;
  conn->queued_xa_start_xid = xid;
  DBUG_VOID_RETURN;
}

void spider_conn_clear_queue(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_conn_clear_queue");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  conn->queued_trx_isolation = FALSE;
  conn->queued_semi_trx_isolation = FALSE;
  conn->queued_autocommit = FALSE;
  conn->queued_sql_log_off = FALSE;
  conn->queued_wait_timeout = FALSE;
  conn->queued_sql_mode = FALSE;
  conn->queued_time_zone = FALSE;
  conn->queued_trx_start = FALSE;
  conn->queued_xa_start = FALSE;
  DBUG_VOID_RETURN;
}

void spider_conn_clear_queue_at_commit(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_conn_clear_queue_at_commit");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  if (conn->queued_trx_start)
  {
    conn->queued_trx_start = FALSE;
    conn->trx_start = FALSE;
  }
  conn->queued_xa_start = FALSE;
  DBUG_VOID_RETURN;
}

void spider_conn_set_timeout(
  SPIDER_CONN *conn,
  uint net_read_timeout,
  uint net_write_timeout
) {
  DBUG_ENTER("spider_conn_set_timeout");
  DBUG_PRINT("info", ("spider conn=%p", conn));
  if (net_read_timeout != conn->net_read_timeout)
  {
    DBUG_PRINT("info",("spider net_read_timeout set from %u to %u",
      conn->net_read_timeout, net_read_timeout));
    conn->queued_net_timeout = TRUE;
    conn->net_read_timeout = net_read_timeout;
  }
  if (net_write_timeout != conn->net_write_timeout)
  {
    DBUG_PRINT("info",("spider net_write_timeout set from %u to %u",
      conn->net_write_timeout, net_write_timeout));
    conn->queued_net_timeout = TRUE;
    conn->net_write_timeout = net_write_timeout;
  }
  DBUG_VOID_RETURN;
}

void spider_conn_set_timeout_from_share(
  SPIDER_CONN *conn,
  int link_idx,
  THD *thd,
  SPIDER_SHARE *share
) {
  DBUG_ENTER("spider_conn_set_timeout_from_share");
  spider_conn_set_timeout(
    conn,
    spider_param_net_read_timeout(thd, share->net_read_timeouts[link_idx]),
    spider_param_net_write_timeout(thd, share->net_write_timeouts[link_idx])
  );
  DBUG_VOID_RETURN;
}

void spider_conn_set_timeout_from_direct_sql(
  SPIDER_CONN *conn,
  THD *thd,
  SPIDER_DIRECT_SQL *direct_sql
) {
  DBUG_ENTER("spider_conn_set_timeout_from_direct_sql");
  spider_conn_set_timeout(
    conn,
    spider_param_net_read_timeout(thd, direct_sql->net_read_timeout),
    spider_param_net_write_timeout(thd, direct_sql->net_write_timeout)
  );
  DBUG_VOID_RETURN;
}

/**
  Insert a connection to a binary tree ordered by priority

  Starting from `top', find the correct spot for `conn' and insert it.
*/
void spider_tree_insert(
  SPIDER_CONN *top,
  SPIDER_CONN *conn
) {
  SPIDER_CONN *current = top;
  longlong priority = conn->priority;
  DBUG_ENTER("spider_tree_insert");
  while (TRUE)
  {
    if (priority < current->priority)
    {
      if (current->c_small == NULL)
      {
        conn->p_small = NULL;
        conn->p_big = current;
        conn->c_small = NULL;
        conn->c_big = NULL;
        current->c_small = conn;
        break;
      } else
        current = current->c_small;
    } else {
      if (current->c_big == NULL)
      {
        conn->p_small = current;
        conn->p_big = NULL;
        conn->c_small = NULL;
        conn->c_big = NULL;
        current->c_big = conn;
        break;
      } else
        current = current->c_big;
    }
  }
  DBUG_VOID_RETURN;
}

/* Returns the connection with the smallest priority in a tree */
SPIDER_CONN *spider_tree_first(
  SPIDER_CONN *top
) {
  SPIDER_CONN *current = top;
  DBUG_ENTER("spider_tree_first");
  while (current)
  {
    if (current->c_small == NULL)
      break;
    else
      current = current->c_small;
  }
  DBUG_RETURN(current);
}

/* Returns the connection with the biggest priority in a tree */
SPIDER_CONN *spider_tree_last(
  SPIDER_CONN *top
) {
  SPIDER_CONN *current = top;
  DBUG_ENTER("spider_tree_last");
  while (TRUE)
  {
    if (current->c_big == NULL)
      break;
    else
      current = current->c_big;
  }
  DBUG_RETURN(current);
}

/*
  Returns the next connection

  Find the connection in the tree with the smallest priority that is
  bigger than that of the current connection.
*/
SPIDER_CONN *spider_tree_next(
  SPIDER_CONN *current
) {
  DBUG_ENTER("spider_tree_next");
  if (current->c_big)
    DBUG_RETURN(spider_tree_first(current->c_big));
  while (TRUE)
  {
    if (current->p_big)
      DBUG_RETURN(current->p_big);
    if (!current->p_small)
      DBUG_RETURN(NULL);
    current = current->p_small;
  }
}

SPIDER_CONN *spider_tree_delete(
  SPIDER_CONN *conn,
  SPIDER_CONN *top
) {
  DBUG_ENTER("spider_tree_delete");
  if (conn->p_small)
  {
    if (conn->c_small)
    {
      conn->c_small->p_big = NULL;
      conn->c_small->p_small = conn->p_small;
      conn->p_small->c_big = conn->c_small;
      if (conn->c_big)
      {
        SPIDER_CONN *last = spider_tree_last(conn->c_small);
        conn->c_big->p_small = last;
        last->c_big = conn->c_big;
      }
    } else if (conn->c_big)
    {
      conn->c_big->p_small = conn->p_small;
      conn->p_small->c_big = conn->c_big;
    } else
      conn->p_small->c_big = NULL;
  } else if (conn->p_big)
  {
    if (conn->c_small)
    {
      conn->c_small->p_big = conn->p_big;
      conn->p_big->c_small = conn->c_small;
      if (conn->c_big)
      {
        SPIDER_CONN *last = spider_tree_last(conn->c_small);
        conn->c_big->p_small = last;
        last->c_big = conn->c_big;
      }
    } else if (conn->c_big)
    {
      conn->c_big->p_big = conn->p_big;
      conn->c_big->p_small = NULL;
      conn->p_big->c_small = conn->c_big;
    } else
      conn->p_big->c_small = NULL;
  } else {
    if (conn->c_small)
    {
      conn->c_small->p_big = NULL;
      conn->c_small->p_small = NULL;
      if (conn->c_big)
      {
        SPIDER_CONN *last = spider_tree_last(conn->c_small);
        conn->c_big->p_small = last;
        last->c_big = conn->c_big;
      }
      DBUG_RETURN(conn->c_small);
    } else if (conn->c_big)
    {
      conn->c_big->p_small = NULL;
      DBUG_RETURN(conn->c_big);
    }
    DBUG_RETURN(NULL);
  }
  DBUG_RETURN(top);
}

int spider_set_conn_bg_param(
  ha_spider *spider
) {
  int error_num, roop_count, bgs_mode;
  SPIDER_SHARE *share = spider->share;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  SPIDER_WIDE_HANDLER *wide_handler = spider->wide_handler;
  THD *thd = wide_handler->trx->thd;
  DBUG_ENTER("spider_set_conn_bg_param");
  DBUG_PRINT("info",("spider spider=%p", spider));
  bgs_mode =
    spider_param_bgs_mode(thd, share->bgs_mode);
  if (bgs_mode == 0)
    result_list->bgs_phase = 0;
  else if (
    bgs_mode <= 2 &&
    (wide_handler->external_lock_type == F_WRLCK ||
      wide_handler->lock_mode == 2)
  )
    result_list->bgs_phase = 0;
  else if (bgs_mode <= 1 && wide_handler->lock_mode == 1)
    result_list->bgs_phase = 0;
  else {
    result_list->bgs_phase = 1;

    result_list->bgs_split_read = spider_bg_split_read_param(spider);
    if (spider->use_pre_call)
    {
      DBUG_PRINT("info",("spider use_pre_call=TRUE"));
      result_list->bgs_first_read = result_list->bgs_split_read;
      result_list->bgs_second_read = result_list->bgs_split_read;
    } else {
      DBUG_PRINT("info",("spider use_pre_call=FALSE"));
      result_list->bgs_first_read =
        spider_param_bgs_first_read(thd, share->bgs_first_read);
      result_list->bgs_second_read =
        spider_param_bgs_second_read(thd, share->bgs_second_read);
    }
    DBUG_PRINT("info",("spider bgs_split_read=%lld",
      result_list->bgs_split_read));
    DBUG_PRINT("info",("spider bgs_first_read=%lld", share->bgs_first_read));
    DBUG_PRINT("info",("spider bgs_second_read=%lld", share->bgs_second_read));

    result_list->split_read =
      result_list->bgs_first_read > 0 ?
      result_list->bgs_first_read :
      result_list->bgs_split_read;
  }

  if (result_list->bgs_phase > 0)
  {
    if (spider->use_fields)
    {
      SPIDER_LINK_IDX_CHAIN *link_idx_chain;
      spider_fields *fields = spider->fields;
      fields->set_pos_to_first_link_idx_chain();
      while ((link_idx_chain = fields->get_next_link_idx_chain()))
      {
        if ((error_num = spider_create_conn_thread(link_idx_chain->conn)))
          DBUG_RETURN(error_num);
      }
    } else {
      for (
        roop_count = spider_conn_link_idx_next(share->link_statuses,
          spider->conn_link_idx, -1, share->link_count,
          spider->wide_handler->lock_mode ?
          SPIDER_LINK_STATUS_RECOVERY : SPIDER_LINK_STATUS_OK);
        roop_count < (int) share->link_count;
        roop_count = spider_conn_link_idx_next(share->link_statuses,
          spider->conn_link_idx, roop_count, share->link_count,
          spider->wide_handler->lock_mode ?
          SPIDER_LINK_STATUS_RECOVERY : SPIDER_LINK_STATUS_OK)
      ) {
        if ((error_num = spider_create_conn_thread(spider->conns[roop_count])))
          DBUG_RETURN(error_num);
      }
    }
  }
  DBUG_RETURN(0);
}

/**
  Creates a background thread on `conn' to run `spider_bg_conn_action()'

  Does not create when `conn' is NULL or a bg thread has already been
  created for `conn'.
*/
int spider_create_conn_thread(
  SPIDER_CONN *conn
) {
  int error_num;
  DBUG_ENTER("spider_create_conn_thread");
  if (conn && !conn->bg_init)
  {
    if (mysql_mutex_init(spd_key_mutex_bg_conn_chain,
      &conn->bg_conn_chain_mutex, MY_MUTEX_INIT_FAST))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_chain_mutex_init;
    }
    conn->bg_conn_chain_mutex_ptr = NULL;
    if (mysql_mutex_init(spd_key_mutex_bg_conn_sync,
      &conn->bg_conn_sync_mutex, MY_MUTEX_INIT_FAST))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_sync_mutex_init;
    }
    if (mysql_mutex_init(spd_key_mutex_bg_conn, &conn->bg_conn_mutex,
      MY_MUTEX_INIT_FAST))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_mutex_init;
    }
    if (mysql_mutex_init(spd_key_mutex_bg_job_stack, &conn->bg_job_stack_mutex,
      MY_MUTEX_INIT_FAST))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_job_stack_mutex_init;
    }
    if (SPD_INIT_DYNAMIC_ARRAY2(&conn->bg_job_stack, sizeof(void *), NULL, 16,
      16, MYF(MY_WME)))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_job_stack_init;
    }
    spider_alloc_calc_mem_init(conn->bg_job_stack, SPD_MID_CREATE_CONN_THREAD_1);
    spider_alloc_calc_mem(spider_current_trx,
      conn->bg_job_stack,
      conn->bg_job_stack.max_element *
      conn->bg_job_stack.size_of_element);
    conn->bg_job_stack_cur_pos = 0;
    if (mysql_cond_init(spd_key_cond_bg_conn_sync,
      &conn->bg_conn_sync_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_sync_cond_init;
    }
    if (mysql_cond_init(spd_key_cond_bg_conn,
      &conn->bg_conn_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_cond_init;
    }
    pthread_mutex_lock(&conn->bg_conn_mutex);
    if (mysql_thread_create(spd_key_thd_bg, &conn->bg_thread,
      &spider_pt_attr, spider_bg_conn_action, (void *) conn)
    )
    {
      pthread_mutex_unlock(&conn->bg_conn_mutex);
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_thread_create;
    }
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
    pthread_mutex_unlock(&conn->bg_conn_mutex);
    pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
    if (!conn->bg_init)
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_thread_create;
    }
  }
  DBUG_RETURN(0);

error_thread_create:
  pthread_cond_destroy(&conn->bg_conn_cond);
error_cond_init:
  pthread_cond_destroy(&conn->bg_conn_sync_cond);
error_sync_cond_init:
  spider_free_mem_calc(spider_current_trx,
    conn->bg_job_stack_id,
    conn->bg_job_stack.max_element *
    conn->bg_job_stack.size_of_element);
  delete_dynamic(&conn->bg_job_stack);
error_job_stack_init:
  pthread_mutex_destroy(&conn->bg_job_stack_mutex);
error_job_stack_mutex_init:
  pthread_mutex_destroy(&conn->bg_conn_mutex);
error_mutex_init:
  pthread_mutex_destroy(&conn->bg_conn_sync_mutex);
error_sync_mutex_init:
  pthread_mutex_destroy(&conn->bg_conn_chain_mutex);
error_chain_mutex_init:
  DBUG_RETURN(error_num);
}

void spider_free_conn_thread(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_free_conn_thread");
  if (conn->bg_init)
  {
    spider_bg_conn_break(conn, NULL);
    pthread_mutex_lock(&conn->bg_conn_mutex);
    conn->bg_kill = TRUE;
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
    pthread_cond_signal(&conn->bg_conn_cond);
    pthread_mutex_unlock(&conn->bg_conn_mutex);
    pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
    pthread_join(conn->bg_thread, NULL);
    pthread_cond_destroy(&conn->bg_conn_cond);
    pthread_cond_destroy(&conn->bg_conn_sync_cond);
    spider_free_mem_calc(spider_current_trx,
      conn->bg_job_stack_id,
      conn->bg_job_stack.max_element *
      conn->bg_job_stack.size_of_element);
    delete_dynamic(&conn->bg_job_stack);
    pthread_mutex_destroy(&conn->bg_job_stack_mutex);
    pthread_mutex_destroy(&conn->bg_conn_mutex);
    pthread_mutex_destroy(&conn->bg_conn_sync_mutex);
    pthread_mutex_destroy(&conn->bg_conn_chain_mutex);
    conn->bg_kill = FALSE;
    conn->bg_init = FALSE;
  }
  DBUG_VOID_RETURN;
}

void spider_bg_conn_wait(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_bg_conn_wait");
  if (conn->bg_init)
  {
    pthread_mutex_lock(&conn->bg_conn_mutex);
    pthread_mutex_unlock(&conn->bg_conn_mutex);
  }
  DBUG_VOID_RETURN;
}

void spider_bg_all_conn_wait(
  ha_spider *spider
) {
  int roop_count;
  SPIDER_CONN *conn;
  SPIDER_SHARE *share = spider->share;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  DBUG_ENTER("spider_bg_all_conn_wait");
  for (
    roop_count = spider_conn_link_idx_next(share->link_statuses,
      spider->conn_link_idx, -1, share->link_count,
      SPIDER_LINK_STATUS_RECOVERY);
    roop_count < (int) share->link_count;
    roop_count = spider_conn_link_idx_next(share->link_statuses,
      spider->conn_link_idx, roop_count, share->link_count,
      SPIDER_LINK_STATUS_RECOVERY)
  ) {
    conn = spider->conns[roop_count];
    if (conn && result_list->bgs_working)
      spider_bg_conn_wait(conn);
  }
  DBUG_VOID_RETURN;
}

int spider_bg_all_conn_pre_next(
  ha_spider *spider,
  int link_idx
) {
  int roop_start, roop_end, roop_count, lock_mode, link_ok, error_num;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  SPIDER_SHARE *share = spider->share;
  DBUG_ENTER("spider_bg_all_conn_pre_next");
  if (result_list->bgs_phase > 0)
  {
    lock_mode = spider_conn_lock_mode(spider);
    if (lock_mode)
    {
      /* "for update" or "lock in share mode" */
      link_ok = spider_conn_link_idx_next(share->link_statuses,
        spider->conn_link_idx, -1, share->link_count,
        SPIDER_LINK_STATUS_OK);
      roop_start = spider_conn_link_idx_next(share->link_statuses,
        spider->conn_link_idx, -1, share->link_count,
        SPIDER_LINK_STATUS_RECOVERY);
      roop_end = spider->share->link_count;
    } else {
      link_ok = link_idx;
      roop_start = link_idx;
      roop_end = link_idx + 1;
    }

    for (roop_count = roop_start; roop_count < roop_end;
      roop_count = spider_conn_link_idx_next(share->link_statuses,
        spider->conn_link_idx, roop_count, share->link_count,
        SPIDER_LINK_STATUS_RECOVERY)
    ) {
      if ((error_num = spider_bg_conn_search(spider, roop_count, roop_start,
        TRUE, TRUE, (roop_count != link_ok))))
        DBUG_RETURN(error_num);
    }
  }
  DBUG_RETURN(0);
}

void spider_bg_conn_break(
  SPIDER_CONN *conn,
  ha_spider *spider
) {
  DBUG_ENTER("spider_bg_conn_break");
  if (
    conn->bg_init &&
    conn->bg_thd != current_thd &&
    (
      !spider ||
      (
        spider->result_list.bgs_working &&
        conn->bg_target == spider
      )
    )
  ) {
    conn->bg_break = TRUE;
    pthread_mutex_lock(&conn->bg_conn_mutex);
    pthread_mutex_unlock(&conn->bg_conn_mutex);
    conn->bg_break = FALSE;
  }
  DBUG_VOID_RETURN;
}

void spider_bg_all_conn_break(
  ha_spider *spider
) {
  int roop_count;
  SPIDER_CONN *conn;
  SPIDER_SHARE *share = spider->share;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  DBUG_ENTER("spider_bg_all_conn_break");
  for (
    roop_count = spider_conn_link_idx_next(share->link_statuses,
      spider->conn_link_idx, -1, share->link_count,
      SPIDER_LINK_STATUS_RECOVERY);
    roop_count < (int) share->link_count;
    roop_count = spider_conn_link_idx_next(share->link_statuses,
      spider->conn_link_idx, roop_count, share->link_count,
      SPIDER_LINK_STATUS_RECOVERY)
  ) {
    conn = spider->conns[roop_count];
    if (conn && result_list->bgs_working)
      spider_bg_conn_break(conn, spider);
    if (spider->quick_targets[roop_count])
    {
      spider_db_free_one_quick_result((SPIDER_RESULT *) result_list->current);
      DBUG_ASSERT(spider->quick_targets[roop_count] == conn->quick_target);
      DBUG_PRINT("info", ("spider conn[%p]->quick_target=NULL", conn));
      conn->quick_target = NULL;
      spider->quick_targets[roop_count] = NULL;
    }
  }
  DBUG_VOID_RETURN;
}

bool spider_bg_conn_get_job(
  SPIDER_CONN *conn
) {
  DBUG_ENTER("spider_bg_conn_get_job");
  pthread_mutex_lock(&conn->bg_job_stack_mutex);
  if (conn->bg_job_stack_cur_pos >= conn->bg_job_stack.elements)
  {
    DBUG_PRINT("info",("spider bg all jobs are completed"));
    conn->bg_get_job_stack_off = FALSE;
    pthread_mutex_unlock(&conn->bg_job_stack_mutex);
    DBUG_RETURN(FALSE);
  }
  DBUG_PRINT("info",("spider bg get job %u",
    conn->bg_job_stack_cur_pos));
  conn->bg_target = ((void **) (conn->bg_job_stack.buffer +
    conn->bg_job_stack.size_of_element * conn->bg_job_stack_cur_pos))[0];
  conn->bg_job_stack_cur_pos++;
  if (conn->bg_job_stack_cur_pos == conn->bg_job_stack.elements)
  {
    DBUG_PRINT("info",("spider bg shift job stack"));
    conn->bg_job_stack_cur_pos = 0;
    conn->bg_job_stack.elements = 0;
  }
  pthread_mutex_unlock(&conn->bg_job_stack_mutex);
  DBUG_RETURN(TRUE);
}

int spider_bg_conn_search(
  ha_spider *spider,
  int link_idx,
  int first_link_idx,
  bool first,
  bool pre_next,
  bool discard_result
) {
  int error_num;
  SPIDER_CONN *conn, *first_conn = NULL;
  SPIDER_RESULT_LIST *result_list = &spider->result_list;
  bool with_lock = FALSE;
  DBUG_ENTER("spider_bg_conn_search");
  DBUG_PRINT("info",("spider spider=%p", spider));
    conn = spider->conns[link_idx];
    with_lock = (spider_conn_lock_mode(spider) != SPIDER_LOCK_MODE_NO_LOCK);
    first_conn = spider->conns[first_link_idx];
  if (first)
  {
    if (spider->use_pre_call)
    {
      DBUG_PRINT("info",("spider skip bg first search"));
    } else {
      DBUG_PRINT("info",("spider bg first search"));
      pthread_mutex_lock(&conn->bg_conn_mutex);
      result_list->bgs_working = TRUE;
      conn->bg_search = TRUE;
      conn->bg_caller_wait = TRUE;
      conn->bg_target = spider;
      conn->link_idx = link_idx;
      conn->bg_discard_result = discard_result;
      pthread_mutex_lock(&conn->bg_conn_sync_mutex);
      pthread_cond_signal(&conn->bg_conn_cond);
      pthread_mutex_unlock(&conn->bg_conn_mutex);
      pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
      pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
      conn->bg_caller_wait = FALSE;
      if (result_list->bgs_error)
      {
        if (result_list->bgs_error_with_message)
          my_message(result_list->bgs_error,
            result_list->bgs_error_msg, MYF(0));
        DBUG_RETURN(result_list->bgs_error);
      }
    }
    if (result_list->bgs_working || !result_list->finish_flg)
    {
      pthread_mutex_lock(&conn->bg_conn_mutex);
      if (!result_list->finish_flg)
      {
        DBUG_PRINT("info",("spider bg second search"));
        if (!spider->use_pre_call || pre_next)
        {
          if (result_list->bgs_error)
          {
            pthread_mutex_unlock(&conn->bg_conn_mutex);
            DBUG_PRINT("info",("spider bg error"));
            if (result_list->bgs_error == HA_ERR_END_OF_FILE)
            {
              DBUG_PRINT("info",("spider bg current->finish_flg=%s",
                result_list->current ?
                (result_list->current->finish_flg ? "TRUE" : "FALSE") : "NULL"));
              DBUG_RETURN(0);
            }
            if (result_list->bgs_error_with_message)
              my_message(result_list->bgs_error,
                result_list->bgs_error_msg, MYF(0));
            DBUG_RETURN(result_list->bgs_error);
          }
          DBUG_PRINT("info",("spider result_list->quick_mode=%d",
            result_list->quick_mode));
          DBUG_PRINT("info",("spider result_list->bgs_current->result=%p",
            result_list->bgs_current->result));
          if (
            result_list->quick_mode == 0 ||
            !result_list->bgs_current->result
          ) {
            DBUG_PRINT("info",("spider result_list->bgs_second_read=%lld",
              result_list->bgs_second_read));
            DBUG_PRINT("info",("spider result_list->bgs_split_read=%lld",
              result_list->bgs_split_read));
            result_list->split_read =
              result_list->bgs_second_read > 0 ?
              result_list->bgs_second_read :
              result_list->bgs_split_read;
            result_list->limit_num =
              result_list->internal_limit - result_list->record_num >=
              result_list->split_read ?
              result_list->split_read :
              result_list->internal_limit - result_list->record_num;
            {
              if ((error_num = spider->reappend_limit_sql_part(
                result_list->internal_offset + result_list->record_num,
                result_list->limit_num,
                SPIDER_SQL_TYPE_SELECT_SQL)))
              {
                pthread_mutex_unlock(&conn->bg_conn_mutex);
                DBUG_RETURN(error_num);
              }
              if (
                !result_list->use_union &&
                (error_num = spider->append_select_lock_sql_part(
                  SPIDER_SQL_TYPE_SELECT_SQL))
              ) {
                pthread_mutex_unlock(&conn->bg_conn_mutex);
                DBUG_RETURN(error_num);
              }
            }
          }
          result_list->bgs_phase = 2;
          if (conn->db_conn->limit_mode() == 1)
          {
            conn->db_conn->set_limit(result_list->limit_num);
            if (!discard_result)
            {
              if ((error_num = spider_db_store_result_for_reuse_cursor(
                spider, link_idx, result_list->table)))
              {
                pthread_mutex_unlock(&conn->bg_conn_mutex);
                DBUG_RETURN(error_num);
              }
            }
            pthread_mutex_unlock(&conn->bg_conn_mutex);
            DBUG_RETURN(0);
          }
        }
        result_list->bgs_working = TRUE;
        conn->bg_search = TRUE;
        if (with_lock)
          conn->bg_conn_chain_mutex_ptr = &first_conn->bg_conn_chain_mutex;
        conn->bg_caller_sync_wait = TRUE;
        conn->bg_target = spider;
        conn->link_idx = link_idx;
        conn->bg_discard_result = discard_result;
        conn->link_idx_chain = spider->link_idx_chain;
        pthread_mutex_lock(&conn->bg_conn_sync_mutex);
        pthread_cond_signal(&conn->bg_conn_cond);
        pthread_mutex_unlock(&conn->bg_conn_mutex);
        pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
        pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
        conn->bg_caller_sync_wait = FALSE;
      } else {
        pthread_mutex_unlock(&conn->bg_conn_mutex);
        DBUG_PRINT("info",("spider bg current->finish_flg=%s",
          result_list->current ?
          (result_list->current->finish_flg ? "TRUE" : "FALSE") : "NULL"));
        if (result_list->bgs_error)
        {
          DBUG_PRINT("info",("spider bg error"));
          if (result_list->bgs_error != HA_ERR_END_OF_FILE)
          {
            if (result_list->bgs_error_with_message)
              my_message(result_list->bgs_error,
                result_list->bgs_error_msg, MYF(0));
            DBUG_RETURN(result_list->bgs_error);
          }
        }
      }
    } else {
      DBUG_PRINT("info",("spider bg current->finish_flg=%s",
        result_list->current ?
        (result_list->current->finish_flg ? "TRUE" : "FALSE") : "NULL"));
      if (result_list->bgs_error)
      {
        DBUG_PRINT("info",("spider bg error"));
        if (result_list->bgs_error != HA_ERR_END_OF_FILE)
        {
          if (result_list->bgs_error_with_message)
            my_message(result_list->bgs_error,
              result_list->bgs_error_msg, MYF(0));
          DBUG_RETURN(result_list->bgs_error);
        }
      }
    }
  } else {
    DBUG_PRINT("info",("spider bg search"));
    if (result_list->current->finish_flg)
    {
      DBUG_PRINT("info",("spider bg end of file"));
      result_list->table->status = STATUS_NOT_FOUND;
      DBUG_RETURN(HA_ERR_END_OF_FILE);
    }
    if (result_list->bgs_working)
    {
      /* wait */
      DBUG_PRINT("info",("spider bg working wait"));
      pthread_mutex_lock(&conn->bg_conn_mutex);
      pthread_mutex_unlock(&conn->bg_conn_mutex);
    }
    if (result_list->bgs_error)
    {
      DBUG_PRINT("info",("spider bg error"));
      if (result_list->bgs_error == HA_ERR_END_OF_FILE)
      {
        result_list->current = result_list->current->next;
        result_list->current_row_num = 0;
        result_list->table->status = STATUS_NOT_FOUND;
      }
      if (result_list->bgs_error_with_message)
        my_message(result_list->bgs_error,
          result_list->bgs_error_msg, MYF(0));
      DBUG_RETURN(result_list->bgs_error);
    }
    result_list->current = result_list->current->next;
    result_list->current_row_num = 0;
    if (result_list->current == result_list->bgs_current)
    {
      DBUG_PRINT("info",("spider bg next search"));
      if (!result_list->current->finish_flg)
      {
        DBUG_PRINT("info",("spider result_list->quick_mode=%d",
          result_list->quick_mode));
        DBUG_PRINT("info",("spider result_list->bgs_current->result=%p",
          result_list->bgs_current->result));
        pthread_mutex_lock(&conn->bg_conn_mutex);
        result_list->bgs_phase = 3;
        if (
          result_list->quick_mode == 0 ||
          !result_list->bgs_current->result
        ) {
          result_list->split_read = result_list->bgs_split_read;
          result_list->limit_num =
            result_list->internal_limit - result_list->record_num >=
            result_list->split_read ?
            result_list->split_read :
            result_list->internal_limit - result_list->record_num;
          {
            if ((error_num = spider->reappend_limit_sql_part(
              result_list->internal_offset + result_list->record_num,
              result_list->limit_num,
              SPIDER_SQL_TYPE_SELECT_SQL)))
            {
              pthread_mutex_unlock(&conn->bg_conn_mutex);
              DBUG_RETURN(error_num);
            }
            if (
              !result_list->use_union &&
              (error_num = spider->append_select_lock_sql_part(
                SPIDER_SQL_TYPE_SELECT_SQL))
            ) {
              pthread_mutex_unlock(&conn->bg_conn_mutex);
              DBUG_RETURN(error_num);
            }
          }
          if (conn->db_conn->limit_mode() == 1)
          {
            conn->db_conn->set_limit(result_list->limit_num);
            if (!discard_result)
            {
              if ((error_num = spider_db_store_result_for_reuse_cursor(
                spider, link_idx, result_list->table)))
              {
                pthread_mutex_unlock(&conn->bg_conn_mutex);
                DBUG_RETURN(error_num);
              }
            }
            pthread_mutex_unlock(&conn->bg_conn_mutex);
            DBUG_RETURN(0);
          }
        }
        conn->bg_target = spider;
        conn->link_idx = link_idx;
        conn->bg_discard_result = discard_result;
        conn->link_idx_chain = spider->link_idx_chain;
        result_list->bgs_working = TRUE;
        conn->bg_search = TRUE;
        if (with_lock)
          conn->bg_conn_chain_mutex_ptr = &first_conn->bg_conn_chain_mutex;
        conn->bg_caller_sync_wait = TRUE;
        pthread_mutex_lock(&conn->bg_conn_sync_mutex);
        pthread_cond_signal(&conn->bg_conn_cond);
        pthread_mutex_unlock(&conn->bg_conn_mutex);
        pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
        pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
        conn->bg_caller_sync_wait = FALSE;
      }
    }
  }
  DBUG_RETURN(0);
}

void spider_bg_conn_simple_action(
  SPIDER_CONN *conn,
  uint simple_action,
  bool caller_wait,
  void *target,
  uint link_idx,
  int *error_num
) {
  DBUG_ENTER("spider_bg_conn_simple_action");
  pthread_mutex_lock(&conn->bg_conn_mutex);
  conn->bg_target = target;
  conn->link_idx = link_idx;
  conn->bg_simple_action = simple_action;
  conn->bg_error_num = error_num;
  if (caller_wait)
  {
    conn->bg_caller_wait = TRUE;
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
  } else {
    conn->bg_caller_sync_wait = TRUE;
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
  }
  pthread_cond_signal(&conn->bg_conn_cond);
  pthread_mutex_unlock(&conn->bg_conn_mutex);
  if (caller_wait)
  {
    pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
    conn->bg_caller_wait = FALSE;
  } else {
    pthread_cond_wait(&conn->bg_conn_sync_cond, &conn->bg_conn_sync_mutex);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
    conn->bg_caller_sync_wait = FALSE;
  }
  DBUG_VOID_RETURN;
}

void *spider_bg_conn_action(
  void *arg
) {
  int error_num;
  SPIDER_CONN *conn = (SPIDER_CONN*) arg;
  SPIDER_TRX *trx;
  ha_spider *spider;
  SPIDER_RESULT_LIST *result_list;
  THD *thd;
  my_thread_init();
  DBUG_ENTER("spider_bg_conn_action");
  /* init start */
  if (!(thd = SPIDER_new_THD(next_thread_id())))
  {
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
    pthread_cond_signal(&conn->bg_conn_sync_cond);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  SPIDER_set_next_thread_id(thd);
#ifdef HAVE_PSI_INTERFACE
  mysql_thread_set_psi_id(thd->thread_id);
#endif
  thd->thread_stack = (char*) &thd;
  thd->store_globals();
  if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
  {
    delete thd;
    pthread_mutex_lock(&conn->bg_conn_sync_mutex);
    pthread_cond_signal(&conn->bg_conn_sync_cond);
    pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  /* lex_start(thd); */
  conn->bg_thd = thd;
  pthread_mutex_lock(&conn->bg_conn_mutex);
  pthread_mutex_lock(&conn->bg_conn_sync_mutex);
  pthread_cond_signal(&conn->bg_conn_sync_cond);
  conn->bg_init = TRUE;
  pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
  /* init end */

  while (TRUE)
  {
    if (conn->bg_conn_chain_mutex_ptr)
    {
      pthread_mutex_unlock(conn->bg_conn_chain_mutex_ptr);
      conn->bg_conn_chain_mutex_ptr = NULL;
    }
    thd->clear_error();
    pthread_cond_wait(&conn->bg_conn_cond, &conn->bg_conn_mutex);
    DBUG_PRINT("info",("spider bg roop start"));
#ifndef DBUG_OFF
    DBUG_PRINT("info",("spider conn->thd=%p", conn->thd));
    if (conn->thd)
    {
      DBUG_PRINT("info",("spider query_id=%lld", conn->thd->query_id));
    }
#endif
    if (conn->bg_caller_sync_wait)
    {
      pthread_mutex_lock(&conn->bg_conn_sync_mutex);
      if (conn->bg_direct_sql)
        conn->bg_get_job_stack_off = TRUE;
      pthread_cond_signal(&conn->bg_conn_sync_cond);
      pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
      if (conn->bg_conn_chain_mutex_ptr)
      {
        pthread_mutex_lock(conn->bg_conn_chain_mutex_ptr);
        if ((&conn->bg_conn_chain_mutex) != conn->bg_conn_chain_mutex_ptr)
        {
          pthread_mutex_unlock(conn->bg_conn_chain_mutex_ptr);
          conn->bg_conn_chain_mutex_ptr = NULL;
        }
      }
    }
    if (conn->bg_kill)
    {
      DBUG_PRINT("info",("spider bg kill start"));
      if (conn->bg_conn_chain_mutex_ptr)
      {
        pthread_mutex_unlock(conn->bg_conn_chain_mutex_ptr);
        conn->bg_conn_chain_mutex_ptr = NULL;
      }
      spider_free_trx(trx, TRUE);
      /* lex_end(thd->lex); */
      delete thd;
      pthread_mutex_lock(&conn->bg_conn_sync_mutex);
      pthread_cond_signal(&conn->bg_conn_sync_cond);
      pthread_mutex_unlock(&conn->bg_conn_mutex);
      pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
      set_current_thd(nullptr);
#endif
      my_thread_end();
      DBUG_RETURN(NULL);
    }
    if (conn->bg_get_job_stack)
    {
      conn->bg_get_job_stack = FALSE;
      if (!spider_bg_conn_get_job(conn))
      {
        conn->bg_direct_sql = FALSE;
      }
    }
    if (conn->bg_search)
    {
      SPIDER_SHARE *share;
      spider_db_handler *dbton_handler;
      DBUG_PRINT("info",("spider bg search start"));
      spider = (ha_spider*) conn->bg_target;
      share = spider->share;
      dbton_handler = spider->dbton_handler[conn->dbton_id];
      result_list = &spider->result_list;
      result_list->bgs_error = 0;
      result_list->bgs_error_with_message = FALSE;
      if (
        result_list->quick_mode == 0 ||
        result_list->bgs_phase == 1 ||
        !result_list->bgs_current->result
      ) {
        ulong sql_type;
        sql_type= SPIDER_SQL_TYPE_SELECT_SQL | SPIDER_SQL_TYPE_TMP_SQL;
        if (spider->use_fields)
        {
          if ((error_num = dbton_handler->set_sql_for_exec(sql_type,
            conn->link_idx, conn->link_idx_chain)))
          {
            result_list->bgs_error = error_num;
            if ((result_list->bgs_error_with_message = thd->is_error()))
              strmov(result_list->bgs_error_msg, spider_stmt_da_message(thd));
          }
        } else {
          if ((error_num = dbton_handler->set_sql_for_exec(sql_type,
            conn->link_idx)))
          {
            result_list->bgs_error = error_num;
            if ((result_list->bgs_error_with_message = thd->is_error()))
              strmov(result_list->bgs_error_msg, spider_stmt_da_message(thd));
          }
        }
        /* todo: is it ok if the following statement is not locked? */
        sql_type &= ~SPIDER_SQL_TYPE_TMP_SQL;
        DBUG_PRINT("info",("spider sql_type=%lu", sql_type));
        if (!result_list->bgs_error)
        {
          spider_lock_before_query(conn, &spider->need_mons[conn->link_idx]);
            if (!(result_list->bgs_error =
              spider_db_set_names(spider, conn, conn->link_idx)))
            {
              if (
                result_list->tmp_table_join && spider->bka_mode != 2 &&
                spider_bit_is_set(result_list->tmp_table_join_first,
                  conn->link_idx)
              ) {
                spider_clear_bit(result_list->tmp_table_join_first,
                  conn->link_idx);
                spider_set_bit(result_list->tmp_table_created,
                  conn->link_idx);
                result_list->tmp_tables_created = TRUE;
                spider_conn_set_timeout_from_share(conn, conn->link_idx,
                  spider->wide_handler->trx->thd, share);
                if (dbton_handler->execute_sql(
                  SPIDER_SQL_TYPE_TMP_SQL,
                  conn,
                  -1,
                  &spider->need_mons[conn->link_idx])
                ) {
                  result_list->bgs_error = spider_db_errorno(conn);
                  if ((result_list->bgs_error_with_message = thd->is_error()))
                    strmov(result_list->bgs_error_msg,
                      spider_stmt_da_message(thd));
                } else
                  spider_db_discard_multiple_result(spider, conn->link_idx,
                    conn);
              }
              if (!result_list->bgs_error)
              {
                spider_conn_set_timeout_from_share(conn, conn->link_idx,
                  spider->wide_handler->trx->thd, share);
                if (dbton_handler->execute_sql(
                  sql_type,
                  conn,
                  result_list->quick_mode,
                  &spider->need_mons[conn->link_idx])
                ) {
                  result_list->bgs_error = spider_db_errorno(conn);
                  if ((result_list->bgs_error_with_message = thd->is_error()))
                    strmov(result_list->bgs_error_msg,
                      spider_stmt_da_message(thd));
                } else {
                  spider->connection_ids[conn->link_idx] = conn->connection_id;
                  if (!conn->bg_discard_result)
                  {
                    if (!(result_list->bgs_error =
                      spider_db_store_result(spider, conn->link_idx,
                        result_list->table)))
                      spider->result_link_idx = conn->link_idx;
                    else {
                      if ((result_list->bgs_error_with_message =
                        thd->is_error()))
                        strmov(result_list->bgs_error_msg,
                          spider_stmt_da_message(thd));
                    }
                  } else {
                    result_list->bgs_error = 0;
                    spider_db_discard_result(spider, conn->link_idx, conn);
                  }
                }
              }
            } else {
              if ((result_list->bgs_error_with_message = thd->is_error()))
                strmov(result_list->bgs_error_msg,
                  spider_stmt_da_message(thd));
            }
            spider_unlock_after_query(conn, 0);
        }
      } else {
        spider->connection_ids[conn->link_idx] = conn->connection_id;
        pthread_mutex_assert_not_owner(&conn->mta_conn_mutex);
        DBUG_ASSERT(!conn->mta_conn_mutex_unlock_later);
        conn->mta_conn_mutex_unlock_later = TRUE;
        result_list->bgs_error =
          spider_db_store_result(spider, conn->link_idx, result_list->table);
        if ((result_list->bgs_error_with_message = thd->is_error()))
          strmov(result_list->bgs_error_msg, spider_stmt_da_message(thd));
        DBUG_ASSERT(conn->mta_conn_mutex_unlock_later);
        conn->mta_conn_mutex_unlock_later = FALSE;
      }
      conn->bg_search = FALSE;
      result_list->bgs_working = FALSE;
      if (conn->bg_caller_wait)
      {
        pthread_mutex_lock(&conn->bg_conn_sync_mutex);
        pthread_cond_signal(&conn->bg_conn_sync_cond);
        pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
      }
      continue;
    }
    if (conn->bg_direct_sql)
    {
      bool is_error = FALSE;
      DBUG_PRINT("info",("spider bg direct sql start"));
      do {
        SPIDER_DIRECT_SQL *direct_sql = (SPIDER_DIRECT_SQL *) conn->bg_target;
        if (
          (error_num = spider_db_udf_direct_sql(direct_sql))
        ) {
          if (thd->is_error())
          {
            if (
              direct_sql->error_rw_mode &&
              spider_db_conn_is_network_error(error_num)
            ) {
              thd->clear_error();
            } else {
              SPIDER_BG_DIRECT_SQL *bg_direct_sql =
                (SPIDER_BG_DIRECT_SQL *) direct_sql->parent;
              pthread_mutex_lock(direct_sql->bg_mutex);
              bg_direct_sql->bg_error = spider_stmt_da_sql_errno(thd);
              strmov((char *) bg_direct_sql->bg_error_msg,
                spider_stmt_da_message(thd));
              pthread_mutex_unlock(direct_sql->bg_mutex);
              is_error = TRUE;
            }
          }
        }
        if (direct_sql->modified_non_trans_table)
        {
          SPIDER_BG_DIRECT_SQL *bg_direct_sql =
            (SPIDER_BG_DIRECT_SQL *) direct_sql->parent;
          pthread_mutex_lock(direct_sql->bg_mutex);
          bg_direct_sql->modified_non_trans_table = TRUE;
          pthread_mutex_unlock(direct_sql->bg_mutex);
        }
        spider_udf_free_direct_sql_alloc(direct_sql, TRUE);
      } while (!is_error && spider_bg_conn_get_job(conn));
      if (is_error)
      {
        while (spider_bg_conn_get_job(conn))
          spider_udf_free_direct_sql_alloc(
            (SPIDER_DIRECT_SQL *) conn->bg_target, TRUE);
      }
      conn->bg_direct_sql = FALSE;
      continue;
    }
    if (conn->bg_exec_sql)
    {
      DBUG_PRINT("info",("spider bg exec sql start"));
      spider = (ha_spider*) conn->bg_target;
      spider_lock_before_query(conn, &spider->need_mons[conn->link_idx]);
      *conn->bg_error_num = spider_db_query_with_set_names(
        conn->bg_sql_type,
        spider,
        conn,
        conn->link_idx
      );
      spider_unlock_after_query(conn, 0);
      conn->bg_exec_sql = FALSE;
      continue;
    }
    if (conn->bg_simple_action)
    {
      switch (conn->bg_simple_action)
      {
        case SPIDER_SIMPLE_CONNECT:
          conn->db_conn->bg_connect();
          break;
        case SPIDER_SIMPLE_DISCONNECT:
          conn->db_conn->bg_disconnect();
          break;
        default:
          spider = (ha_spider*) conn->bg_target;
          *conn->bg_error_num =
            spider_db_simple_action(conn->bg_simple_action,
              spider->dbton_handler[conn->dbton_id], conn->link_idx);
          break;
      }
      conn->bg_simple_action = SPIDER_SIMPLE_NO_ACTION;
      if (conn->bg_caller_wait)
      {
        pthread_mutex_lock(&conn->bg_conn_sync_mutex);
        pthread_cond_signal(&conn->bg_conn_sync_cond);
        pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
      }
      continue;
    }
    if (conn->bg_break)
    {
      DBUG_PRINT("info",("spider bg break start"));
      spider = (ha_spider*) conn->bg_target;
      result_list = &spider->result_list;
      result_list->bgs_working = FALSE;
      continue;
    }
  }
}

int spider_create_sts_thread(
  SPIDER_SHARE *share
) {
  int error_num;
  DBUG_ENTER("spider_create_sts_thread");
  if (!share->bg_sts_init)
  {
    if (mysql_cond_init(spd_key_cond_bg_sts,
      &share->bg_sts_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_cond_init;
    }
    if (mysql_cond_init(spd_key_cond_bg_sts_sync,
      &share->bg_sts_sync_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_sync_cond_init;
    }
    if (mysql_thread_create(spd_key_thd_bg_sts, &share->bg_sts_thread,
      &spider_pt_attr, spider_bg_sts_action, (void *) share)
    )
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_thread_create;
    }
    share->bg_sts_init = TRUE;
  }
  DBUG_RETURN(0);

error_thread_create:
  pthread_cond_destroy(&share->bg_sts_sync_cond);
error_sync_cond_init:
  pthread_cond_destroy(&share->bg_sts_cond);
error_cond_init:
  DBUG_RETURN(error_num);
}

void spider_free_sts_thread(
  SPIDER_SHARE *share
) {
  DBUG_ENTER("spider_free_sts_thread");
  if (share->bg_sts_init)
  {
    pthread_mutex_lock(&share->sts_mutex);
    share->bg_sts_kill = TRUE;
    pthread_cond_signal(&share->bg_sts_cond);
    pthread_cond_wait(&share->bg_sts_sync_cond, &share->sts_mutex);
    pthread_mutex_unlock(&share->sts_mutex);
    pthread_join(share->bg_sts_thread, NULL);
    pthread_cond_destroy(&share->bg_sts_sync_cond);
    pthread_cond_destroy(&share->bg_sts_cond);
    share->bg_sts_thd_wait = FALSE;
    share->bg_sts_kill = FALSE;
    share->bg_sts_init = FALSE;
  }
  DBUG_VOID_RETURN;
}

void *spider_bg_sts_action(
  void *arg
) {
  SPIDER_SHARE *share = (SPIDER_SHARE*) arg;
  SPIDER_TRX *trx;
  int error_num = 0, roop_count;
  ha_spider spider;
  SPIDER_WIDE_HANDLER wide_handler;
  int *need_mons;
  SPIDER_CONN **conns;
  uint *conn_link_idx;
  uchar *conn_can_fo;
  char **conn_keys;
  spider_db_handler **dbton_hdl;
  THD *thd;
  my_thread_init();
  DBUG_ENTER("spider_bg_sts_action");
  /* init start */
  char *ptr;
  ptr = (char *) my_alloca(
    (sizeof(int) * share->link_count) +
    (sizeof(SPIDER_CONN *) * share->link_count) +
    (sizeof(uint) * share->link_count) +
    (sizeof(uchar) * share->link_bitmap_size) +
    (sizeof(char *) * share->link_count) +
    (sizeof(spider_db_handler *) * SPIDER_DBTON_SIZE));
  if (!ptr)
  {
    pthread_mutex_lock(&share->sts_mutex);
    share->bg_sts_thd_wait = FALSE;
    share->bg_sts_kill = FALSE;
    share->bg_sts_init = FALSE;
    pthread_mutex_unlock(&share->sts_mutex);
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  need_mons = (int *) ptr;
  ptr += (sizeof(int) * share->link_count);
  conns = (SPIDER_CONN **) ptr;
  ptr += (sizeof(SPIDER_CONN *) * share->link_count);
  conn_link_idx = (uint *) ptr;
  ptr += (sizeof(uint) * share->link_count);
  conn_can_fo = (uchar *) ptr;
  ptr += (sizeof(uchar) * share->link_bitmap_size);
  conn_keys = (char **) ptr;
  ptr += (sizeof(char *) * share->link_count);
  dbton_hdl = (spider_db_handler **) ptr;
  pthread_mutex_lock(&share->sts_mutex);
  if (!(thd = SPIDER_new_THD(next_thread_id())))
  {
    share->bg_sts_thd_wait = FALSE;
    share->bg_sts_kill = FALSE;
    share->bg_sts_init = FALSE;
    pthread_mutex_unlock(&share->sts_mutex);
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  SPIDER_set_next_thread_id(thd);
#ifdef HAVE_PSI_INTERFACE
  mysql_thread_set_psi_id(thd->thread_id);
#endif
  thd->thread_stack = (char*) &thd;
  thd->store_globals();
  if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
  {
    delete thd;
    share->bg_sts_thd_wait = FALSE;
    share->bg_sts_kill = FALSE;
    share->bg_sts_init = FALSE;
    pthread_mutex_unlock(&share->sts_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  share->bg_sts_thd = thd;
  spider.wide_handler = &wide_handler;
  wide_handler.trx = trx;
  spider.share = share;
  spider.conns = conns;
  spider.conn_link_idx = conn_link_idx;
  spider.conn_can_fo = conn_can_fo;
  spider.need_mons = need_mons;
  spider.conn_keys_first_ptr = share->conn_keys[0];
  spider.conn_keys = conn_keys;
  spider.dbton_handler = dbton_hdl;
  memset(conns, 0, sizeof(SPIDER_CONN *) * share->link_count);
  memset(need_mons, 0, sizeof(int) * share->link_count);
  memset(dbton_hdl, 0, sizeof(spider_db_handler *) * SPIDER_DBTON_SIZE);
  spider_trx_set_link_idx_for_all(&spider);
  spider.search_link_idx = spider_conn_first_link_idx(thd,
    share->link_statuses, share->access_balances, spider.conn_link_idx,
    share->link_count, SPIDER_LINK_STATUS_OK);
  for (roop_count = 0; roop_count < SPIDER_DBTON_SIZE; roop_count++)
  {
    if (
      spider_bit_is_set(share->dbton_bitmap, roop_count) &&
      spider_dbton[roop_count].create_db_handler
    ) {
      if (!(dbton_hdl[roop_count] = spider_dbton[roop_count].create_db_handler(
        &spider, share->dbton_share[roop_count])))
        break;
      if (dbton_hdl[roop_count]->init())
        break;
    }
  }
  if (roop_count < SPIDER_DBTON_SIZE)
  {
    DBUG_PRINT("info",("spider handler init error"));
    for (roop_count = SPIDER_DBTON_SIZE - 1; roop_count >= 0; --roop_count)
    {
      if (
        spider_bit_is_set(share->dbton_bitmap, roop_count) &&
        dbton_hdl[roop_count]
      ) {
        delete dbton_hdl[roop_count];
        dbton_hdl[roop_count] = NULL;
      }
    }
    spider_free_trx(trx, TRUE);
    delete thd;
    share->bg_sts_thd_wait = FALSE;
    share->bg_sts_kill = FALSE;
    share->bg_sts_init = FALSE;
    pthread_mutex_unlock(&share->sts_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  /* init end */

  while (TRUE)
  {
    DBUG_PRINT("info",("spider bg sts roop start"));
    if (share->bg_sts_kill)
    {
      DBUG_PRINT("info",("spider bg sts kill start"));
      for (roop_count = SPIDER_DBTON_SIZE - 1; roop_count >= 0; --roop_count)
      {
        if (
          spider_bit_is_set(share->dbton_bitmap, roop_count) &&
          dbton_hdl[roop_count]
        ) {
          delete dbton_hdl[roop_count];
          dbton_hdl[roop_count] = NULL;
        }
      }
      spider_free_trx(trx, TRUE);
      delete thd;
      pthread_cond_signal(&share->bg_sts_sync_cond);
      pthread_mutex_unlock(&share->sts_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
      set_current_thd(nullptr);
#endif
      my_thread_end();
      my_afree(need_mons);
      DBUG_RETURN(NULL);
    }
    if (spider.search_link_idx < 0)
    {
      spider_trx_set_link_idx_for_all(&spider);
/*
      spider.search_link_idx = spider_conn_next_link_idx(
        thd, share->link_statuses, share->access_balances,
        spider.conn_link_idx, spider.search_link_idx, share->link_count,
        SPIDER_LINK_STATUS_OK);
*/
      spider.search_link_idx = spider_conn_first_link_idx(thd,
        share->link_statuses, share->access_balances, spider.conn_link_idx,
        share->link_count, SPIDER_LINK_STATUS_OK);
    }
    if (spider.search_link_idx >= 0)
    {
      if (difftime(share->bg_sts_try_time, share->sts_get_time) >=
        share->bg_sts_interval)
      {
        if (!conns[spider.search_link_idx])
        {
          spider_get_conn(share, spider.search_link_idx,
            share->conn_keys[spider.search_link_idx],
            trx, &spider, FALSE, FALSE, SPIDER_CONN_KIND_MYSQL,
            &error_num);
          conns[spider.search_link_idx]->error_mode = 0;
          spider.search_link_idx = -1;
        }
        if (spider.search_link_idx != -1 && conns[spider.search_link_idx])
        {
          if (spider_get_sts(share, spider.search_link_idx,
            share->bg_sts_try_time, &spider,
            share->bg_sts_interval, share->bg_sts_mode,
            share->bg_sts_sync,
            2, HA_STATUS_CONST | HA_STATUS_VARIABLE))
          {
            spider.search_link_idx = -1;
          }
        }
      }
    }
    memset(need_mons, 0, sizeof(int) * share->link_count);
    share->bg_sts_thd_wait = TRUE;
    pthread_cond_wait(&share->bg_sts_cond, &share->sts_mutex);
  }
}

int spider_create_crd_thread(
  SPIDER_SHARE *share
) {
  int error_num;
  DBUG_ENTER("spider_create_crd_thread");
  if (!share->bg_crd_init)
  {
    if (mysql_cond_init(spd_key_cond_bg_crd,
      &share->bg_crd_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_cond_init;
    }
    if (mysql_cond_init(spd_key_cond_bg_crd_sync,
      &share->bg_crd_sync_cond, NULL))
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_sync_cond_init;
    }
    if (mysql_thread_create(spd_key_thd_bg_crd, &share->bg_crd_thread,
      &spider_pt_attr, spider_bg_crd_action, (void *) share)
    )
    {
      error_num = HA_ERR_OUT_OF_MEM;
      goto error_thread_create;
    }
    share->bg_crd_init = TRUE;
  }
  DBUG_RETURN(0);

error_thread_create:
  pthread_cond_destroy(&share->bg_crd_sync_cond);
error_sync_cond_init:
  pthread_cond_destroy(&share->bg_crd_cond);
error_cond_init:
  DBUG_RETURN(error_num);
}

void spider_free_crd_thread(
  SPIDER_SHARE *share
) {
  DBUG_ENTER("spider_free_crd_thread");
  if (share->bg_crd_init)
  {
    pthread_mutex_lock(&share->crd_mutex);
    share->bg_crd_kill = TRUE;
    pthread_cond_signal(&share->bg_crd_cond);
    pthread_cond_wait(&share->bg_crd_sync_cond, &share->crd_mutex);
    pthread_mutex_unlock(&share->crd_mutex);
    pthread_join(share->bg_crd_thread, NULL);
    pthread_cond_destroy(&share->bg_crd_sync_cond);
    pthread_cond_destroy(&share->bg_crd_cond);
    share->bg_crd_thd_wait = FALSE;
    share->bg_crd_kill = FALSE;
    share->bg_crd_init = FALSE;
  }
  DBUG_VOID_RETURN;
}

void *spider_bg_crd_action(
  void *arg
) {
  SPIDER_SHARE *share = (SPIDER_SHARE*) arg;
  SPIDER_TRX *trx;
  int error_num = 0, roop_count;
  ha_spider spider;
  SPIDER_WIDE_HANDLER wide_handler;
  TABLE table;
  int *need_mons;
  SPIDER_CONN **conns;
  uint *conn_link_idx;
  uchar *conn_can_fo;
  char **conn_keys;
  spider_db_handler **dbton_hdl;
  THD *thd;
  my_thread_init();
  DBUG_ENTER("spider_bg_crd_action");
  /* init start */
  char *ptr;
  ptr = (char *) my_alloca(
    (sizeof(int) * share->link_count) +
    (sizeof(SPIDER_CONN *) * share->link_count) +
    (sizeof(uint) * share->link_count) +
    (sizeof(uchar) * share->link_bitmap_size) +
    (sizeof(char *) * share->link_count) +
    (sizeof(spider_db_handler *) * SPIDER_DBTON_SIZE));
  if (!ptr)
  {
    pthread_mutex_lock(&share->crd_mutex);
    share->bg_crd_thd_wait = FALSE;
    share->bg_crd_kill = FALSE;
    share->bg_crd_init = FALSE;
    pthread_mutex_unlock(&share->crd_mutex);
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  need_mons = (int *) ptr;
  ptr += (sizeof(int) * share->link_count);
  conns = (SPIDER_CONN **) ptr;
  ptr += (sizeof(SPIDER_CONN *) * share->link_count);
  conn_link_idx = (uint *) ptr;
  ptr += (sizeof(uint) * share->link_count);
  conn_can_fo = (uchar *) ptr;
  ptr += (sizeof(uchar) * share->link_bitmap_size);
  conn_keys = (char **) ptr;
  ptr += (sizeof(char *) * share->link_count);
  dbton_hdl = (spider_db_handler **) ptr;
  pthread_mutex_lock(&share->crd_mutex);
  if (!(thd = SPIDER_new_THD(next_thread_id())))
  {
    share->bg_crd_thd_wait = FALSE;
    share->bg_crd_kill = FALSE;
    share->bg_crd_init = FALSE;
    pthread_mutex_unlock(&share->crd_mutex);
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  SPIDER_set_next_thread_id(thd);
#ifdef HAVE_PSI_INTERFACE
  mysql_thread_set_psi_id(thd->thread_id);
#endif
  thd->thread_stack = (char*) &thd;
  thd->store_globals();
  if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
  {
    delete thd;
    share->bg_crd_thd_wait = FALSE;
    share->bg_crd_kill = FALSE;
    share->bg_crd_init = FALSE;
    pthread_mutex_unlock(&share->crd_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  share->bg_crd_thd = thd;
  table.s = share->table_share;
  table.field = share->table_share->field;
  table.key_info = share->table_share->key_info;
  spider.wide_handler = &wide_handler;
  wide_handler.trx = trx;
  spider.change_table_ptr(&table, share->table_share);
  spider.share = share;
  spider.conns = conns;
  spider.conn_link_idx = conn_link_idx;
  spider.conn_can_fo = conn_can_fo;
  spider.need_mons = need_mons;
  spider.conn_keys_first_ptr = share->conn_keys[0];
  spider.conn_keys = conn_keys;
  spider.dbton_handler = dbton_hdl;
  memset(conns, 0, sizeof(SPIDER_CONN *) * share->link_count);
  memset(need_mons, 0, sizeof(int) * share->link_count);
  memset(dbton_hdl, 0, sizeof(spider_db_handler *) * SPIDER_DBTON_SIZE);
  spider_trx_set_link_idx_for_all(&spider);
  spider.search_link_idx = spider_conn_first_link_idx(thd,
    share->link_statuses, share->access_balances, spider.conn_link_idx,
    share->link_count, SPIDER_LINK_STATUS_OK);
  for (roop_count = 0; roop_count < SPIDER_DBTON_SIZE; roop_count++)
  {
    if (
      spider_bit_is_set(share->dbton_bitmap, roop_count) &&
      spider_dbton[roop_count].create_db_handler
    ) {
      if (!(dbton_hdl[roop_count] = spider_dbton[roop_count].create_db_handler(
        &spider, share->dbton_share[roop_count])))
        break;
      if (dbton_hdl[roop_count]->init())
        break;
    }
  }
  if (roop_count < SPIDER_DBTON_SIZE)
  {
    DBUG_PRINT("info",("spider handler init error"));
    for (roop_count = SPIDER_DBTON_SIZE - 1; roop_count >= 0; --roop_count)
    {
      if (
        spider_bit_is_set(share->dbton_bitmap, roop_count) &&
        dbton_hdl[roop_count]
      ) {
        delete dbton_hdl[roop_count];
        dbton_hdl[roop_count] = NULL;
      }
    }
    spider_free_trx(trx, TRUE);
    delete thd;
    share->bg_crd_thd_wait = FALSE;
    share->bg_crd_kill = FALSE;
    share->bg_crd_init = FALSE;
    pthread_mutex_unlock(&share->crd_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    my_afree(need_mons);
    DBUG_RETURN(NULL);
  }
  /* init end */

  while (TRUE)
  {
    DBUG_PRINT("info",("spider bg crd roop start"));
    if (share->bg_crd_kill)
    {
      DBUG_PRINT("info",("spider bg crd kill start"));
      for (roop_count = SPIDER_DBTON_SIZE - 1; roop_count >= 0; --roop_count)
      {
        if (
          spider_bit_is_set(share->dbton_bitmap, roop_count) &&
          dbton_hdl[roop_count]
        ) {
          delete dbton_hdl[roop_count];
          dbton_hdl[roop_count] = NULL;
        }
      }
      spider_free_trx(trx, TRUE);
      delete thd;
      pthread_cond_signal(&share->bg_crd_sync_cond);
      pthread_mutex_unlock(&share->crd_mutex);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
      set_current_thd(nullptr);
#endif
      my_thread_end();
      my_afree(need_mons);
      DBUG_RETURN(NULL);
    }
    if (spider.search_link_idx < 0)
    {
      spider_trx_set_link_idx_for_all(&spider);
      spider.search_link_idx = spider_conn_first_link_idx(thd,
        share->link_statuses, share->access_balances, spider.conn_link_idx,
        share->link_count, SPIDER_LINK_STATUS_OK);
    }
    if (spider.search_link_idx >= 0)
    {
      if (difftime(share->bg_crd_try_time, share->crd_get_time) >=
        share->bg_crd_interval)
      {
        if (!conns[spider.search_link_idx])
        {
          spider_get_conn(share, spider.search_link_idx,
            share->conn_keys[spider.search_link_idx],
            trx, &spider, FALSE, FALSE, SPIDER_CONN_KIND_MYSQL,
            &error_num);
          conns[spider.search_link_idx]->error_mode = 0;
          spider.search_link_idx = -1;
        }
        if (spider.search_link_idx != -1 && conns[spider.search_link_idx])
        {
          if (spider_get_crd(share, spider.search_link_idx,
            share->bg_crd_try_time, &spider, &table,
            share->bg_crd_interval, share->bg_crd_mode,
            share->bg_crd_sync,
            2))
          {
            spider.search_link_idx = -1;
          }
        }
      }
    }
    memset(need_mons, 0, sizeof(int) * share->link_count);
    share->bg_crd_thd_wait = TRUE;
    pthread_cond_wait(&share->bg_crd_cond, &share->crd_mutex);
  }
}

int spider_create_mon_threads(
  SPIDER_TRX *trx,
  SPIDER_SHARE *share
) {
  bool create_bg_mons = FALSE;
  int error_num, roop_count, roop_count2;
  SPIDER_LINK_PACK link_pack;
  SPIDER_TABLE_MON_LIST *table_mon_list;
  DBUG_ENTER("spider_create_mon_threads");
  if (!share->bg_mon_init)
  {
    for (roop_count = 0; roop_count < (int) share->all_link_count;
      roop_count++)
    {
      if (share->monitoring_bg_kind[roop_count])
      {
        create_bg_mons = TRUE;
        break;
      }
    }
    if (create_bg_mons)
    {
      char link_idx_str[SPIDER_SQL_INT_LEN];
      int link_idx_str_length;
      char *buf = (char *) my_alloca(share->table_name_length + SPIDER_SQL_INT_LEN + 1);
      spider_string conv_name_str(buf, share->table_name_length +
        SPIDER_SQL_INT_LEN + 1, system_charset_info);
      conv_name_str.init_calc_mem(SPD_MID_CREATE_MON_THREADS_1);
      conv_name_str.length(0);
      conv_name_str.q_append(share->table_name, share->table_name_length);
      for (roop_count = 0; roop_count < (int) share->all_link_count;
        roop_count++)
      {
        if (share->monitoring_bg_kind[roop_count])
        {
          conv_name_str.length(share->table_name_length);
          if (share->static_link_ids[roop_count])
          {
            memcpy(link_idx_str, share->static_link_ids[roop_count],
              share->static_link_ids_lengths[roop_count] + 1);
            link_idx_str_length = share->static_link_ids_lengths[roop_count];
          } else {
            link_idx_str_length = my_sprintf(link_idx_str, (link_idx_str,
              "%010d", roop_count));
          }
          conv_name_str.q_append(link_idx_str, link_idx_str_length + 1);
          conv_name_str.length(conv_name_str.length() - 1);
          if (!(table_mon_list = spider_get_ping_table_mon_list(trx, trx->thd,
            &conv_name_str, share->table_name_length, roop_count,
            share->static_link_ids[roop_count],
            share->static_link_ids_lengths[roop_count],
            (uint32) share->monitoring_sid[roop_count], FALSE, &error_num)))
          {
            my_afree(buf);
            goto error_get_ping_table_mon_list;
          }
          spider_free_ping_table_mon_list(table_mon_list);
        }
      }
      if (!(share->bg_mon_thds = (THD **)
        spider_bulk_malloc(spider_current_trx, SPD_MID_CREATE_MON_THREADS_2, MYF(MY_WME | MY_ZEROFILL),
          &share->bg_mon_thds,
            (uint) (sizeof(THD *) * share->all_link_count),
          &share->bg_mon_threads,
            (uint) (sizeof(pthread_t) * share->all_link_count),
          &share->bg_mon_mutexes,
            (uint) (sizeof(pthread_mutex_t) * share->all_link_count),
          &share->bg_mon_conds,
            (uint) (sizeof(pthread_cond_t) * share->all_link_count),
          &share->bg_mon_sleep_conds,
            (uint) (sizeof(pthread_cond_t) * share->all_link_count),
          NullS))
      ) {
        error_num = HA_ERR_OUT_OF_MEM;
        my_afree(buf);
        goto error_alloc_base;
      }
      for (roop_count = 0; roop_count < (int) share->all_link_count;
        roop_count++)
      {
        if (
          share->monitoring_bg_kind[roop_count] &&
          mysql_mutex_init(spd_key_mutex_bg_mon,
            &share->bg_mon_mutexes[roop_count], MY_MUTEX_INIT_FAST)
        ) {
          error_num = HA_ERR_OUT_OF_MEM;
          my_afree(buf);
          goto error_mutex_init;
        }
      }
      for (roop_count = 0; roop_count < (int) share->all_link_count;
        roop_count++)
      {
        if (
          share->monitoring_bg_kind[roop_count] &&
          mysql_cond_init(spd_key_cond_bg_mon,
            &share->bg_mon_conds[roop_count], NULL)
        ) {
          error_num = HA_ERR_OUT_OF_MEM;
          my_afree(buf);
          goto error_cond_init;
        }
      }
      for (roop_count = 0; roop_count < (int) share->all_link_count;
        roop_count++)
      {
        if (
          share->monitoring_bg_kind[roop_count] &&
          mysql_cond_init(spd_key_cond_bg_mon_sleep,
            &share->bg_mon_sleep_conds[roop_count], NULL)
        ) {
          error_num = HA_ERR_OUT_OF_MEM;
          my_afree(buf);
          goto error_sleep_cond_init;
        }
      }
      link_pack.share = share;
      for (roop_count = 0; roop_count < (int) share->all_link_count;
        roop_count++)
      {
        if (share->monitoring_bg_kind[roop_count])
        {
          link_pack.link_idx = roop_count;
          pthread_mutex_lock(&share->bg_mon_mutexes[roop_count]);
          if (mysql_thread_create(spd_key_thd_bg_mon,
            &share->bg_mon_threads[roop_count], &spider_pt_attr,
            spider_bg_mon_action, (void *) &link_pack)
          )
          {
            error_num = HA_ERR_OUT_OF_MEM;
            my_afree(buf);
            goto error_thread_create;
          }
          pthread_cond_wait(&share->bg_mon_conds[roop_count],
            &share->bg_mon_mutexes[roop_count]);
          pthread_mutex_unlock(&share->bg_mon_mutexes[roop_count]);
        }
      }
      share->bg_mon_init = TRUE;
      my_afree(buf);
    }
  }
  DBUG_RETURN(0);

error_thread_create:
  roop_count2 = roop_count;
  for (roop_count--; roop_count >= 0; roop_count--)
  {
    if (share->monitoring_bg_kind[roop_count])
      pthread_mutex_lock(&share->bg_mon_mutexes[roop_count]);
  }
  share->bg_mon_kill = TRUE;
  for (roop_count = roop_count2 - 1; roop_count >= 0; roop_count--)
  {
    if (share->monitoring_bg_kind[roop_count])
    {
      pthread_cond_wait(&share->bg_mon_conds[roop_count],
        &share->bg_mon_mutexes[roop_count]);
      pthread_mutex_unlock(&share->bg_mon_mutexes[roop_count]);
    }
  }
  share->bg_mon_kill = FALSE;
  roop_count = share->all_link_count;
error_sleep_cond_init:
  for (roop_count--; roop_count >= 0; roop_count--)
  {
    if (share->monitoring_bg_kind[roop_count])
      pthread_cond_destroy(&share->bg_mon_sleep_conds[roop_count]);
  }
  roop_count = share->all_link_count;
error_cond_init:
  for (roop_count--; roop_count >= 0; roop_count--)
  {
    if (share->monitoring_bg_kind[roop_count])
      pthread_cond_destroy(&share->bg_mon_conds[roop_count]);
  }
  roop_count = share->all_link_count;
error_mutex_init:
  for (roop_count--; roop_count >= 0; roop_count--)
  {
    if (share->monitoring_bg_kind[roop_count])
      pthread_mutex_destroy(&share->bg_mon_mutexes[roop_count]);
  }
  spider_free(spider_current_trx, share->bg_mon_thds, MYF(0));
error_alloc_base:
error_get_ping_table_mon_list:
  DBUG_RETURN(error_num);
}

void spider_free_mon_threads(
  SPIDER_SHARE *share
) {
  int roop_count;
  DBUG_ENTER("spider_free_mon_threads");
  if (share->bg_mon_init)
  {
    for (roop_count = 0; roop_count < (int) share->all_link_count;
      roop_count++)
    {
      if (
        share->monitoring_bg_kind[roop_count] &&
        share->bg_mon_thds[roop_count]
      ) {
        share->bg_mon_thds[roop_count]->killed = SPIDER_THD_KILL_CONNECTION;
      }
    }
    for (roop_count = 0; roop_count < (int) share->all_link_count;
      roop_count++)
    {
      if (share->monitoring_bg_kind[roop_count])
        pthread_mutex_lock(&share->bg_mon_mutexes[roop_count]);
    }
    share->bg_mon_kill = TRUE;
    for (roop_count = 0; roop_count < (int) share->all_link_count;
      roop_count++)
    {
      if (share->monitoring_bg_kind[roop_count])
      {
        pthread_cond_signal(&share->bg_mon_sleep_conds[roop_count]);
        pthread_cond_wait(&share->bg_mon_conds[roop_count],
          &share->bg_mon_mutexes[roop_count]);
        pthread_mutex_unlock(&share->bg_mon_mutexes[roop_count]);
        pthread_join(share->bg_mon_threads[roop_count], NULL);
        pthread_cond_destroy(&share->bg_mon_conds[roop_count]);
        pthread_cond_destroy(&share->bg_mon_sleep_conds[roop_count]);
        pthread_mutex_destroy(&share->bg_mon_mutexes[roop_count]);
      }
    }
    spider_free(spider_current_trx, share->bg_mon_thds, MYF(0));
    share->bg_mon_kill = FALSE;
    share->bg_mon_init = FALSE;
  }
  DBUG_VOID_RETURN;
}

void *spider_bg_mon_action(
  void *arg
) {
  SPIDER_LINK_PACK *link_pack = (SPIDER_LINK_PACK*) arg;
  SPIDER_SHARE *share = link_pack->share;
  SPIDER_TRX *trx;
  int error_num, link_idx = link_pack->link_idx;
  THD *thd;
  my_thread_init();
  DBUG_ENTER("spider_bg_mon_action");
  /* init start */
  pthread_mutex_lock(&share->bg_mon_mutexes[link_idx]);
  if (!(thd = SPIDER_new_THD(next_thread_id())))
  {
    share->bg_mon_kill = FALSE;
    share->bg_mon_init = FALSE;
    pthread_cond_signal(&share->bg_mon_conds[link_idx]);
    pthread_mutex_unlock(&share->bg_mon_mutexes[link_idx]);
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  SPIDER_set_next_thread_id(thd);
#ifdef HAVE_PSI_INTERFACE
  mysql_thread_set_psi_id(thd->thread_id);
#endif
  thd->thread_stack = (char*) &thd;
  thd->store_globals();
  if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
  {
    delete thd;
    share->bg_mon_kill = FALSE;
    share->bg_mon_init = FALSE;
    pthread_cond_signal(&share->bg_mon_conds[link_idx]);
    pthread_mutex_unlock(&share->bg_mon_mutexes[link_idx]);
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
    set_current_thd(nullptr);
#endif
    my_thread_end();
    DBUG_RETURN(NULL);
  }
  share->bg_mon_thds[link_idx] = thd;
  pthread_cond_signal(&share->bg_mon_conds[link_idx]);
/*
  pthread_mutex_unlock(&share->bg_mon_mutexes[link_idx]);
*/
  /* init end */

  while (TRUE)
  {
    DBUG_PRINT("info",("spider bg mon sleep %lld",
      share->monitoring_bg_interval[link_idx]));
    if (!share->bg_mon_kill)
    {
      struct timespec abstime;
      set_timespec_nsec(abstime,
        share->monitoring_bg_interval[link_idx] * 1000);
      pthread_cond_timedwait(&share->bg_mon_sleep_conds[link_idx],
        &share->bg_mon_mutexes[link_idx], &abstime);
    }
    DBUG_PRINT("info",("spider bg mon roop start"));
    if (share->bg_mon_kill)
    {
      DBUG_PRINT("info",("spider bg mon kill start"));
      pthread_cond_signal(&share->bg_mon_conds[link_idx]);
      pthread_mutex_unlock(&share->bg_mon_mutexes[link_idx]);
      spider_free_trx(trx, TRUE);
      delete thd;
#if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
      set_current_thd(nullptr);
#endif
      my_thread_end();
      DBUG_RETURN(NULL);
    }
    if (share->monitoring_bg_kind[link_idx])
    {
      lex_start(thd);
      error_num = spider_ping_table_mon_from_table(
        trx,
        thd,
        share,
        link_idx,
        (uint32) share->monitoring_sid[link_idx],
        share->table_name,
        share->table_name_length,
        link_idx,
        NULL,
        0,
        share->monitoring_bg_kind[link_idx],
        share->monitoring_limit[link_idx],
        share->monitoring_bg_flag[link_idx],
        TRUE
      );
      lex_end(thd->lex);
    }
  }
}

/**
  Returns a random (active) server with a maximum required link status

  Calculate the sum of balances of all servers whose link status is at
  most the specified status ("eligible"), generate a random number
  less than this balance, then find the first server cumulatively
  exceeding this balance

  @param thd              Connection used for generating a random number
  @param link_statuses    The link statuses of servers
  @param access_balances  The access balances of servers
  @param conn_link_idx    Array of indexes to servers
  @param link_count       Number of servers
  @param link_status      The maximum required link status
  @retval Index to the found server
  @retval -1              if no eligible servers
  @retval -2              if out of memory
*/
int spider_conn_first_link_idx(
  THD *thd,
  long *link_statuses,
  long *access_balances,
  uint *conn_link_idx,
  int link_count,
  int link_status
) {
  int roop_count, active_links = 0;
  longlong balance_total = 0, balance_val;
  double rand_val;
  int *link_idxs, link_idx;
  long *balances;
  DBUG_ENTER("spider_conn_first_link_idx");
  char *ptr;
  ptr = (char *) my_alloca((sizeof(int) * link_count) + (sizeof(long) * link_count));
  if (!ptr)
  {
    DBUG_PRINT("info",("spider out of memory"));
    DBUG_RETURN(-2);
  }
  link_idxs = (int *) ptr;
  ptr += sizeof(int) * link_count;
  balances = (long *) ptr;
  for (roop_count = 0; roop_count < link_count; roop_count++)
  {
    DBUG_ASSERT((conn_link_idx[roop_count] - roop_count) % link_count == 0);
    if (link_statuses[conn_link_idx[roop_count]] <= link_status)
    {
      link_idxs[active_links] = roop_count;
      balances[active_links] = access_balances[roop_count];
      balance_total += access_balances[roop_count];
      active_links++;
    }
  }

  if (active_links == 0)
  {
    DBUG_PRINT("info",("spider all links are failed"));
    my_afree(link_idxs);
    DBUG_RETURN(-1);
  }
  DBUG_PRINT("info",("spider server_id=%lu", thd->variables.server_id));
  DBUG_PRINT("info",("spider thread_id=%lu", thd_get_thread_id(thd)));
  rand_val = spider_rand(thd->variables.server_id + thd_get_thread_id(thd));
  DBUG_PRINT("info",("spider rand_val=%f", rand_val));
  balance_val = (longlong) (rand_val * balance_total);
  DBUG_PRINT("info",("spider balance_val=%lld", balance_val));
  for (roop_count = 0; roop_count < active_links - 1; roop_count++)
  {
    DBUG_PRINT("info",("spider balances[%d]=%ld",
      roop_count, balances[roop_count]));
    if (balance_val < balances[roop_count])
      break;
    balance_val -= balances[roop_count];
  }

  DBUG_PRINT("info",("spider first link_idx=%d", link_idxs[roop_count]));
  link_idx = link_idxs[roop_count];
  my_afree(link_idxs);
  DBUG_RETURN(link_idx);
}

int spider_conn_next_link_idx(
  THD *thd,
  long *link_statuses,
  long *access_balances,
  uint *conn_link_idx,
  int link_idx,
  int link_count,
  int link_status
) {
  int tmp_link_idx;
  DBUG_ENTER("spider_conn_next_link_idx");
  DBUG_ASSERT((conn_link_idx[link_idx] - link_idx) % link_count == 0);
  tmp_link_idx = spider_conn_first_link_idx(thd, link_statuses,
    access_balances, conn_link_idx, link_count, link_status);
  if (
    tmp_link_idx >= 0 &&
    tmp_link_idx == link_idx
  ) {
    do {
      tmp_link_idx++;
      if (tmp_link_idx >= link_count)
        tmp_link_idx = 0;
      if (tmp_link_idx == link_idx)
        break;
    } while (link_statuses[conn_link_idx[tmp_link_idx]] > link_status);
    DBUG_PRINT("info",("spider next link_idx=%d", tmp_link_idx));
    DBUG_RETURN(tmp_link_idx);
  }
  DBUG_PRINT("info",("spider next link_idx=%d", tmp_link_idx));
  DBUG_RETURN(tmp_link_idx);
}

/**
  Finds the next active server with a maximum required link status

  @param link_statuses  The statuses of servers
  @param conn_link_idx  The array of active servers
  @param link_idx       The index of the current active server
  @param link_count     The number of active servers
  @param link_status    The required maximum link status
  @return               The next active server whose link status is
                        at most the required one.
*/
int spider_conn_link_idx_next(
  long *link_statuses,
  uint *conn_link_idx,
  int link_idx,
  int link_count,
  int link_status
) {
  DBUG_ENTER("spider_conn_link_idx_next");
  do {
    link_idx++;
    if (link_idx >= link_count)
      break;
    /* Asserts that the `link_idx`th active server is in the correct
    "group" */
    DBUG_ASSERT((conn_link_idx[link_idx] - link_idx) % link_count == 0);
  } while (link_statuses[conn_link_idx[link_idx]] > link_status);
  DBUG_PRINT("info",("spider link_idx=%d", link_idx));
  DBUG_RETURN(link_idx);
}

int spider_conn_get_link_status(
  long *link_statuses,
  uint *conn_link_idx,
  int link_idx
) {
  DBUG_ENTER("spider_conn_get_link_status");
  DBUG_PRINT("info",("spider link_status=%d",
    (int) link_statuses[conn_link_idx[link_idx]]));
  DBUG_RETURN((int) link_statuses[conn_link_idx[link_idx]]);
}

int spider_conn_lock_mode(
  ha_spider *spider
) {
  SPIDER_WIDE_HANDLER *wide_handler = spider->wide_handler;
  DBUG_ENTER("spider_conn_lock_mode");
  if (wide_handler->external_lock_type == F_WRLCK ||
    wide_handler->lock_mode == 2)
    DBUG_RETURN(SPIDER_LOCK_MODE_EXCLUSIVE);
  else if (wide_handler->lock_mode == 1)
    DBUG_RETURN(SPIDER_LOCK_MODE_SHARED);
  DBUG_RETURN(SPIDER_LOCK_MODE_NO_LOCK);
}

bool spider_conn_check_recovery_link(
  SPIDER_SHARE *share
) {
  int roop_count;
  DBUG_ENTER("spider_check_recovery_link");
  for (roop_count = 0; roop_count < (int) share->link_count; roop_count++)
  {
    if (share->link_statuses[roop_count] == SPIDER_LINK_STATUS_RECOVERY)
      DBUG_RETURN(TRUE);
  }
  DBUG_RETURN(FALSE);
}

SPIDER_CONN* spider_get_conn_from_idle_connection(
  SPIDER_SHARE *share,
  int link_idx,
  char *conn_key,
  ha_spider *spider,
  uint conn_kind,
  int base_link_idx,
  int *error_num
  )
{
  DBUG_ENTER("spider_get_conn_from_idle_connection");
  SPIDER_IP_PORT_CONN *ip_port_conn;
  SPIDER_CONN *conn = NULL;
  uint spider_max_connections = spider_param_max_connections();
  struct timespec abstime;
  ulonglong start, inter_val = 0;
  longlong last_ntime = 0;
  ulonglong wait_time = (ulonglong)spider_param_conn_wait_timeout()*1000*1000*1000; // default 10s

  unsigned long ip_port_count = 0; // init 0

  set_timespec(abstime, 0);

  pthread_mutex_lock(&spider_ipport_conn_mutex);
  if ((ip_port_conn = (SPIDER_IP_PORT_CONN*) my_hash_search_using_hash_value(
    &spider_ipport_conns, share->conn_keys_hash_value[link_idx],
    (uchar*) share->conn_keys[link_idx], share->conn_keys_lengths[link_idx])))
  { /* exists */
    pthread_mutex_unlock(&spider_ipport_conn_mutex);
    pthread_mutex_lock(&ip_port_conn->mutex);
    ip_port_count = ip_port_conn->ip_port_count;
  } else {
    pthread_mutex_unlock(&spider_ipport_conn_mutex);
  }

  if (
    ip_port_conn &&
    ip_port_count >= spider_max_connections &&
    spider_max_connections > 0
  ) { /* no idle conn && enable connection pool, wait */
    pthread_mutex_unlock(&ip_port_conn->mutex);
    start = my_hrtime().val;
    while(1)
    {
      int error;
      inter_val = my_hrtime().val - start; // us
      last_ntime = wait_time - inter_val*1000; // *1000, to ns
      if(last_ntime <= 0)
      {/* wait timeout */
        *error_num = ER_SPIDER_CON_COUNT_ERROR;
        DBUG_RETURN(NULL);
      }
      set_timespec_nsec(abstime, last_ntime);
      pthread_mutex_lock(&ip_port_conn->mutex);
      ++ip_port_conn->waiting_count;
      error = pthread_cond_timedwait(&ip_port_conn->cond, &ip_port_conn->mutex, &abstime);
      --ip_port_conn->waiting_count;
      pthread_mutex_unlock(&ip_port_conn->mutex);
      if (error == ETIMEDOUT || error == ETIME || error != 0 )
      {
        *error_num = ER_SPIDER_CON_COUNT_ERROR;
        DBUG_RETURN(NULL);
      }

      pthread_mutex_lock(&spider_conn_mutex);
      if ((conn = (SPIDER_CONN*) my_hash_search_using_hash_value(
        &spider_open_connections, share->conn_keys_hash_value[link_idx],
        (uchar*) share->conn_keys[link_idx],
        share->conn_keys_lengths[link_idx])))
      {
        /* get conn from spider_open_connections, then delete conn in spider_open_connections */
        my_hash_delete(&spider_open_connections, (uchar*) conn);  
        pthread_mutex_unlock(&spider_conn_mutex);
        DBUG_PRINT("info",("spider get global conn"));
        if (spider)
        {
          spider->conns[base_link_idx] = conn;
          if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
            conn->use_for_active_standby = TRUE;
        }
        DBUG_RETURN(conn);
      }
      else
      {
        pthread_mutex_unlock(&spider_conn_mutex);
      }
    }
  }
  else
  { /* create conn */
    if (ip_port_conn)
      pthread_mutex_unlock(&ip_port_conn->mutex);
    DBUG_PRINT("info",("spider create new conn"));
    if (!(conn = spider_create_conn(share, spider, link_idx, base_link_idx, conn_kind, error_num)))
      DBUG_RETURN(conn);
    *conn->conn_key = *conn_key;
    if (spider)
    {
      spider->conns[base_link_idx] = conn;
      if (spider_bit_is_set(spider->conn_can_fo, base_link_idx))
        conn->use_for_active_standby = TRUE;
    }
  }

  DBUG_RETURN(conn);
}


SPIDER_IP_PORT_CONN* spider_create_ipport_conn(SPIDER_CONN *conn)
{
  DBUG_ENTER("spider_create_ipport_conn");
  if (conn)
  {
    SPIDER_IP_PORT_CONN *ret = (SPIDER_IP_PORT_CONN *)
      my_malloc(PSI_INSTRUMENT_ME, sizeof(*ret), MY_ZEROFILL | MY_WME);
    if (!ret)
    {
      goto err_return_direct;
    }

    if (mysql_mutex_init(spd_key_mutex_conn_i, &ret->mutex, MY_MUTEX_INIT_FAST))
    {
      //error
      goto err_malloc_key;
    }

    if (mysql_cond_init(spd_key_cond_conn_i, &ret->cond, NULL))
    {
      pthread_mutex_destroy(&ret->mutex);
      goto err_malloc_key;
      //error
    }

    ret->key_len = conn->conn_key_length;
    if (ret->key_len <= 0) {
      pthread_cond_destroy(&ret->cond);
      pthread_mutex_destroy(&ret->mutex);
      goto err_malloc_key;
    }

    ret->key = (char *) my_malloc(PSI_INSTRUMENT_ME, ret->key_len +
                             conn->tgt_host_length + 1, MY_ZEROFILL | MY_WME);
    if (!ret->key) {
      pthread_cond_destroy(&ret->cond);
      pthread_mutex_destroy(&ret->mutex);
      goto err_malloc_key;
    }
    ret->remote_ip_str = ret->key + ret->key_len;

    memcpy(ret->key, conn->conn_key, ret->key_len);

    memcpy(ret->remote_ip_str, conn->tgt_host, conn->tgt_host_length);
    ret->remote_port = conn->tgt_port;
    ret->conn_id = conn->conn_id;
    ret->ip_port_count = 1; // init

    ret->key_hash_value = conn->conn_key_hash_value;
    DBUG_RETURN(ret);
err_malloc_key:
    spider_my_free(ret, MYF(0));
err_return_direct:
    DBUG_RETURN(NULL);
  }
  DBUG_RETURN(NULL);
}


void spider_free_ipport_conn(void *info)
{
  DBUG_ENTER("spider_free_ipport_conn");
  if (info)
  {
    SPIDER_IP_PORT_CONN *p = (SPIDER_IP_PORT_CONN *)info;
    pthread_cond_destroy(&p->cond);
    pthread_mutex_destroy(&p->mutex);
    spider_my_free(p->key, MYF(0));
    spider_my_free(p, MYF(0));
  }
  DBUG_VOID_RETURN;
}

void spider_lock_before_query(SPIDER_CONN *conn, int *need_mon)
{
  pthread_mutex_assert_not_owner(&conn->mta_conn_mutex);
  pthread_mutex_lock(&conn->mta_conn_mutex);
  conn->need_mon = need_mon;
  DBUG_ASSERT(!conn->mta_conn_mutex_lock_already);
  DBUG_ASSERT(!conn->mta_conn_mutex_unlock_later);
  conn->mta_conn_mutex_lock_already = TRUE;
  conn->mta_conn_mutex_unlock_later = TRUE;
}

int spider_unlock_after_query(SPIDER_CONN *conn, int ret)
{
  DBUG_ASSERT(conn->mta_conn_mutex_lock_already);
  DBUG_ASSERT(conn->mta_conn_mutex_unlock_later);
  conn->mta_conn_mutex_lock_already = FALSE;
  conn->mta_conn_mutex_unlock_later = FALSE;
  pthread_mutex_unlock(&conn->mta_conn_mutex);
  return ret;
}

int spider_unlock_after_query_1(SPIDER_CONN *conn)
{
  DBUG_ASSERT(conn->mta_conn_mutex_lock_already);
  DBUG_ASSERT(conn->mta_conn_mutex_unlock_later);
  conn->mta_conn_mutex_lock_already = FALSE;
  conn->mta_conn_mutex_unlock_later = FALSE;
  return spider_db_errorno(conn);
}

int spider_unlock_after_query_2(SPIDER_CONN *conn, ha_spider *spider, int link_idx, TABLE *table)
{
  DBUG_ASSERT(conn->mta_conn_mutex_lock_already);
  DBUG_ASSERT(conn->mta_conn_mutex_unlock_later);
  conn->mta_conn_mutex_lock_already = FALSE;
  conn->mta_conn_mutex_unlock_later = FALSE;
  return spider_db_store_result(spider, link_idx, table);
}
