Lighttpd

{{{

Restarting FCGI backend without downtime.

In case you have FCGI backend running on local sockets, it's possible to restart FCGI backend so that lighty never sees backend being down.
In short it's that we start backend on temporary socket and when started we rename the socket and then kill the old backend service.

As words don't explain it as good as code does, so here's the code snippet:

1. config
   PHP_FCGI_CHILDREN=5
   SPAWN_SOCKET="/var/run/php/fcgi.sock"
   PHP_FCGI_BINARY=/usr/bin/php.fcgi

1. start new instance
   socket="$SPAWN_SOCKET"
   pid=$(cat /var/run/php-fcgi.pid)
   SPAWN_SOCKET=$(mktemp -p ${SPAWN_SOCKET%/*} ${SPAWN_SOCKET##*/}.XXXXXX) || exit 1
   spawn-fcgi -P /var/run/php-fcgi.pid -f $PHP_FCGI_BINARY -s $SPAWN_SOCKET -C $PHP_FCGI_CHILDREN || exit 1
2. optional
   chown lighttpd $SPAWN_SOCKET
   chgrp lighttpd $SPAWN_SOCKET
3. let lighty use new socket
   mv -f "$SPAWN_SOCKET" "$socket"

1. sleep to let old requests to finish

sleep 10

1. now can stop old instance
   kill $pid
   }}}