haproxy/contrib/systemd/haproxy.service.in
Tim Duesterhus d6942c8297 MEDIUM: mworker: Add systemd Type=notify support
This patch adds support for `Type=notify` to the systemd unit.

Supporting `Type=notify` improves both starting as well as reloading
of the unit, because systemd will be let known when the action completed.

See this quote from `systemd.service(5)`:
> Note however that reloading a daemon by sending a signal (as with the
> example line above) is usually not a good choice, because this is an
> asynchronous operation and hence not suitable to order reloads of
> multiple services against each other. It is strongly recommended to
> set ExecReload= to a command that not only triggers a configuration
> reload of the daemon, but also synchronously waits for it to complete.

By making systemd aware of a reload in progress it is able to wait until
the reload actually succeeded.

This patch introduces both a new `USE_SYSTEMD` build option which controls
including the sd-daemon library as well as a `-Ws` runtime option which
runs haproxy in master-worker mode with systemd support.

When haproxy is running in master-worker mode with systemd support it will
send status messages to systemd using `sd_notify(3)` in the following cases:

- The master process forked off the worker processes (READY=1)
- The master process entered the `mworker_reload()` function (RELOADING=1)
- The master process received the SIGUSR1 or SIGTERM signal (STOPPING=1)

Change the unit file to specify `Type=notify` and replace master-worker
mode (`-W`) with master-worker mode with systemd support (`-Ws`).

Future evolutions of this feature could include making use of the `STATUS`
feature of `sd_notify()` to send information about the number of active
connections to systemd. This would require bidirectional communication
between the master and the workers and thus is left for future work.
2017-11-20 18:39:41 +01:00

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SYSTEMD

[Unit]
Description=HAProxy Load Balancer
After=network.target
[Service]
# You can point the environment variable HAPROXY_STATS_SOCKET to a stats
# socket if you want seamless reloads.
Environment="CONFIG=/etc/haproxy/haproxy.cfg" "PIDFILE=/run/haproxy.pid"
ExecStartPre=@SBINDIR@/haproxy -f $CONFIG -c -q
ExecStart=@SBINDIR@/haproxy -Ws -f $CONFIG -p $PIDFILE
ExecReload=@SBINDIR@/haproxy -f $CONFIG -c -q
ExecReload=/bin/kill -USR2 $MAINPID
KillMode=mixed
Restart=always
Type=notify
[Install]
WantedBy=multi-user.target