run script to spawn a runsvdir subprocess for a multi-instance service

multi-instance-run

#!/usr/bin/env sh
# vim: set ft=sh tw=80 sw=2 ts=2 et :
#
# Environment Variables:
# SV_INSTANCES -- the number of instances to spawn under ./instances
# SV_STOP_WAIT -- controls the shutdown wait time for instances
# SV_NAME -- controls the name of the service -- must not contain directory
#   separators. Defaults to the basename of the current directory.
#
# If an env file is present in the current directory and readable, the run
# script sources it.
#
# A template directory must exist and contain a run file. When instantiating the
# service's instances, the template directory is recursively copied, for each
# instance, into ./instances. Upon stopping, the instance directories are
# destroyed.

if [ -r env ]; then
  . ./env
fi

set --
exec 2>&1

logprefix="$(basename "$PWD"):"
log () {
  echo "${logprefix}" "$@"
}

if [ ! -d template ]; then
  log 'no template directory found'
  exit 1
elif [ ! -x template/run ]; then
  log 'no template/run executable found'
  exit 1
fi

: "${proclog:=log: ...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................}"
wsec="${SV_STOP_WAIT:-20}"
n="${SV_INSTANCES:-1}"
name="${SV_NAME:-$(basename "$PWD")}"
: "${name:=instance}"

if [ ! -d instances ]; then
  if ! mkdir instances; then
    log 'unable to create instances directory'
    exit 1
  fi
fi

runsvdir_pid=''
instance_dir () {
  echo -n "./instances/${name}.$1"
}

cleanup_done=''
cleanup () {
  if [ $cleanup_done ]; then
    return 0
  fi
  cleanup_done=1

  if [ $runsvdir_pid ]; then
    if [ $# -gt 0 ]; then
      sv -w "${wsec}" down "$@"
    fi
    kill -HUP $runsvdir_pid
  fi

  if [ $# -gt 0 ]; then
    rm -rf "$@"
  fi
}

trap 'cleanup "$@"' TERM
for i in `seq -w 1 $n`; do
  i="$(instance_dir "$i")"
  if [ -d "$i" ]; then
    log "service directory already exists: $i"
    sv check "$i"
    svstatus=$?
    # if runsv is down, clean up the old directory
    if [ $svstatus = 1 ]; then
      rm -rf "$i"
    else
      log "$i: service is not reporting as down -- exiting"
      exit 1
    fi
  fi

  set -- "$@" "$i"
  cp -Rpv template "$i"
done

runsvdir "$PWD/instances" "$proclog" &
runsvdir_pid=$!
log started

wait "$runsvdir_pid"
log finished