systemd to FastCGI socket passing compatibility script

systemd-spawn-fcgi.sh

#!/bin/bash

set -e

if [ "${LISTEN_PID}" != $$ ]; then
	echo >&2 "file descriptors not for us, pid not matching: '${LISTEN_PID}' != '$$'"
	exit 255
fi

if [ "${LISTEN_FDS}" != "1" ]; then
	echo >&2 "Requires exactly one socket passed to fastcgi, got: '${LISTEN_FDS:-0}'"
	exit 255
fi

unset LISTEN_FDS

# move socket from 3 to 0
exec 0<&3
exec 3<&-

# spawn fastcgi backend
exec "$@"

Why do you need separate script for it?
Systemd can pass socket as stdin (0), not 3.
See "StandardInput=socket".

Following config works for me:

$ cat munin-cgi-graph.socket
[Unit]
Description=Munin socket

[Socket]
ListenStream=/run/munin/munin-cgi-graph.sock
Accept=false

[Install]
WantedBy=sockets.target


$ cat munin-cgi-graph.service
[Unit]
Description=Munin cgi graphics
After=network.target
Requires=munin-cgi-graph.socket


[Service]
ExecStart=/var/www/cgi-bin/munin-cgi-graph
User=munin
Type=simple
Group=nginx
StandardInput=socket

[Install]
WantedBy=multi-user.target