gitlab: Reduce log retention drastically

This patch instructs gitlab's omnibus image to configure logging to only
retain 5 files for each services which are not larger than 10MiB or
older than a day (default rotation time).

This should help to prevent random crashes/becoming unhealthy, which
seems to originate from a filled up tmpfs for logging.

Reference:
https://docs.gitlab.com/13.11/omnibus/settings/logs.html#runit-logs

roles/gitlab/templates/docker-compose.yml

@@ -176,6 +176,15 @@ services:
 {% endif %}
 {% endif %}
 
+{% if gitlab_log_tmpfs %}
+        # Configure logging to only retain 10 log files, of 10MiB each
+        # This should prevent the tmpfs from overflowing
+        logging['svlogd_size'] = 10 * 1024 * 1024
+        logging['svlogd_num'] = 5
+        logging['logrotate_maxsize'] = 10 * 1024 * 1024
+        logging['logrotate_rotate'] = 5
+{% endif %}
+
     labels:
       - "traefik.http.routers.gitlab.rule=Host(`{{ gitlab_domain }}`) && PathPrefix(`/`)"
       - "traefik.http.routers.gitlab.entrypoints=websecure"