Alpine image using systemd wrapper

[jodawill]

Alpine image using systemd wrapper

[tianon]

It's got systemd in the name because that's the primary use case it was developed for, but it's simply a wrapper that manages a haproxy instance such that zero-downtime configuration reloads can be performed, for example. There's another open issue or PR discussing the syslog issue (don't have the number handy ATM).

[jodawill]

The wrapper adds the (undocumented) -Ds flag to haproxy, which is specific to systemd.

[tianon]

From https://manpages.debian.org/stretch/haproxy/haproxy.1.en.html:

-Ds

Start in systemd daemon mode, keeping a process in foreground.

Keeping a process in the foreground is exactly what we need -- they added it for systemd, because that's how one normally runs processes in systemd, but it's useful for Docker as well (because Docker requires that processes run in the same "foregrounded daemon" way). Even if we weren't using the haproxy-systemd-wrapper, we'd still be using -Ds.

Also, it's our entrypoint script which adds this, and only does so conditionally based on the intended command being simply haproxy, so it should be trivial to bypass at runtime. If you wanted something hacky, you could go as simple as something like the following: (as discussed over in #39)

$ docker run -dit haproxy bash -c 'syslogd -O /proc/1/fd/1 -S -D; exec haproxy -f /usr/local/etc/haproxy/haproxy.cfg -Ds'

[jodawill]

@tianon, thanks for the help. I've done some poking around and I see that haproxy seems to ignore signals unless you're using that wrapper. The thing I don't understand is why logging doesn't work when I start haproxy via the wrapper. I've tried adding syslogd -O /proc/1/fd/1 to the entrypoint script and it doesn't give me any logs. Is this a known bug, or is my configuration wrong somehow?

[tianon]

Sorry for the delay -- that's a quirk of HAProxy: it will only log to syslog. I'm not sure why your starting syslogd didn't work, but there's more discussion of that over in #39.

Closing since the original question here seems to be resolved. 👍