etherpad: redirect container logs

Redirect etherpad container logs via rsyslogd to /var/log/containers,
which is rotated by default.  This avoids some issues we've seen with
the journal becoming too big.

Change-Id: Id557b9265e30acdb2ca09631dbedf034f85a700f

playbooks/roles/etherpad/templates/docker-compose.yaml.j2

@@ -15,11 +15,19 @@ services:
     volumes:
       - /var/etherpad/db:/var/lib/mysql
       - /etc/etherpad/mysql:/etc/mysql/conf.d
+    logging:
+      driver: syslog
+      options:
+        tag: "docker-mariadb"
   etherpad:
     restart: always
     image: docker.io/opendevorg/etherpad
     network_mode: host
     environment:
       NODE_ENV: production
+    logging:
+      driver: syslog
+      options:
+        tag: "docker-etherpad"
     volumes:
       - /etc/etherpad/settings.json:/opt/etherpad-lite/settings.json

testinfra/test_etherpad.py

@@ -25,3 +25,12 @@ def test_etherpad_robots(host):
                    '--resolve etherpad.opendev.org:443:127.0.0.1 '
                    'https://etherpad.opendev.org/robots.txt')
     assert 'Disallow: /' in cmd.stdout
+
+def test_etherpad_logs(host):
+    etherpad_log_file = host.file('/var/log/containers/docker-etherpad.log')
+    assert etherpad_log_file.exists
+    assert etherpad_log_file.contains('Etherpad is running')
+
+    mariadb_log_file = host.file('/var/log/containers/docker-mariadb.log')
+    assert mariadb_log_file.exists
+    assert mariadb_log_file.contains('mysqld: ready for connections')