S6-RC-FDHOLDER-FILLER(8)

NAME
s6-rc-fdholder-filler - create anonymous pipes and store them into an s6-fdholderd(8) “fd-holding” daemon

SYNOPSIS
s6-rc-fdholder-filler [-1] [-t timeout] < longrunnamesfile

DESCRIPTION
s6-rc-fdholder-filler creates anonymous pipes and stores them into an s6-fdholderd(8) “fd-holding” daemon.

s6-rc-fdholder-filler is not meant to be used directly; it is used in internal scripts created by s6-rc-compile(8), which are invoked during an s6-rc(8) execution.

s6-rc-fdholder-filler expects file descriptor 6 to be open and connected to the s6-fdholderd(8) daemon instance managed by s6-rc(8) as the internal s6rc-fdholder service.

It reads a list of longrun names from its stdin, one per line. Empty lines are ignored; comments starting with ‘#’ are ignored; leading whitespace is ignored, but trailing whitespace is not.

For every name longrun that it finds, it creates an anonymous pipe, and stores both ends of that pipe into the s6-fdholderd(8) instance, with the pipe:s6-rc-r-longrun ( for the reading end) and pipe:s6-rc-w-longrun ( for the writing end) identifiers, and an infinite timeout.

It then exits 0.

s6-rc-fdholder-filler is never meant to be used manually; this page should only be used to understand s6-rc internals.

s6-rc-fdholder-filler is used in the ‘s6rc-fdholder’ internal service's run script, right after the s6-fdholderd(8) daemon is started; its arguments are the names of all the consumer longrun services declared in the service database.

The point is to create all the pipes for the longrun pipelines in advance, every time the ‘s6rc-fdholder’ service is started, and make them available in the fd holder. This way, pipelined services can simply retrieve their stdin ( for consumers) or stdout ( for producers) from the fd holder, at any time: even if a pipeline service dies and is restarted, the pipe will remain valid.

If the fd holder itself dies, it will be refilled with a new set of pipes as soon as it is restarted. Pipelined services will not be impacted until one of them restarts; then all the pipeline will restart.

OPTIONS

-1  Write a newline to stdout before exiting after successful operation. This is used as a notification mechanism.

-t timeout
    If the operation cannot be achieved in timeout milliseconds, abort and report failure. By default, timeout is 0, meaning infinite.

EXIT STATUS

0   Success.

100 Wrong usage.

111 System call failed.

SEE ALSO
s6-rc-faq(7), s6-rc-overview(7), s6-rc-why(7), s6-rc(8), s6-rc-bundle(8), s6-rc-compile(8), s6-rc-db(8), s6-rc-dryrun(8), s6-rc-format-upgrade(8), s6-rc-init(8), s6-rc-oneshot-run(8), s6-rc-update(8)

This man page is ported from the authoritative documentation at: https://skarnet.org/software/s6-rc/s6-rc-fdholder-filler.html

AUTHORS
Laurent Bercot Alexis <flexibeast@gmail.com> (man page port)