#781 Add Syslog logging for watcher

[JudgeGregg]

See #781

How to use:

stdout_stream.class = SyslogStream
and
stdout_stream.syslog_url = syslog:///dev/log
or
stdout_stream.syslog_url = syslog://127.0.0.1:514?user

"ident" attribute can also be passed as an argument:
stdout_stream.ident = my_ident

If using a local UNIX socket (/dev/log):

• it's a simple wrapper of the standard lib syslog call
• facility is set to 'user'
• priority is set to 'info'

If using remote address:

• protocol is UDP only
• facility depends on the syslog url, defaults to 'user'
• priority is set to 'info'

Tests use a simple UDP socket for remote syslog.
I don't know how to test a local syslog.

Thank you for your work on circus :)

[k4nar]

Thank you for your contribution!

I wonder if this isn't already supported by the logoutput option documented here: https://circus.readthedocs.io/en/latest/for-ops/configuration/ .

[JudgeGregg]

I may be wrong, but I believe this setting is for the circusd master process, and I could'nt find a way to apply the same configuration for watchers?

With the following config, my watcher's stdout goes to the terminal:

[circus]
logoutput = syslog:///dev/log?user

[watcher:foo]
cmd = python
args = -u foo.py
numprocesses = 1

But it's also perfectly possible that I just overlooked a setting in the configuration file :)

[k4nar]

I've never tried to use this. But the doc clearly indicates that it should be the way to log to Syslog, so if it doesn't work I think we should fix it before introducing a new option for it 😄 .

logoutput
The logoutput file where we want to log (default: - to log on stdout). You can log to a remote syslog by using the following syntax: syslog://host:port?facility where host is your syslog server, port is optional and facility is the syslog facility to use. If you wish to log to a local syslog you can use syslog:///path/to/syslog/socket?facility instead.

[MFlossmann]

I've never tried to use this. But the doc clearly indicates that it should be the way to log to Syslog, so if it doesn't work I think we should fix it before introducing a new option for it smile .

logoutput
The logoutput file where we want to log (default: - to log on stdout). You can log to a remote syslog by using the following syntax: syslog://host:port?facility where host is your syslog server, port is optional and facility is the syslog facility to use. If you wish to log to a local syslog you can use syslog:///path/to/syslog/socket?facility instead.

This only applies to the arbiter, i.e. the circusd, but not the watchers. The watchers don't have an option to stream to syslog (edit: As JudgeGregg pointed out).