This started with me wondering why gerritbot was putting all its
output into /var/log/syslog -- it turns out Xenial docker is
configured to use journalctl (which forwards to syslog) and Bionic
onwards uses json-file.
Both are sub-optimial; but particularly the json-file because we lose
the logs when the container dies. This proposes moving to a more
standard model of having the containers log to syslog and redirecting
that to files on disk.
Install a rsyslog configuration to capture "docker-*" program names
and put them into logfiles in /var/log/containers. Also install
rotation for these files.
In an initial group of docker-compose files, setup logging to syslog
which should then be captured into these files. Add some basic
testing.
If this works OK, I think we can standardise our docker-compose files
like this to caputure the logs the same everywhere.
Change-Id: I940a5b05057e832e2efad79d9a2ed5325020ed0c
694241ad77