Add logrotate template rendered upon installation

There are no logrotate configurations for the mysql router logs.
This PR introduces a template rendered upon installation of the charm.
A maximum of 10 log files (10M each) are retained.

Change-Id: I18376228af4ca809c10a1b138ceb96459686daa4
Closes-Bug: #1880083

src/lib/charm/openstack/mysql_router.py

@@ -66,6 +66,11 @@ class MySQLRouterCharm(charms_openstack.charm.OpenStackCharm):
         "/etc/systemd/system",
         "{}.service".format(name))
 
+    logrotate_file = os.path.join(
+        "/etc/logrotate.d",
+        "{}".format(name)
+    )
+
     services = [name]
     restart_map = {
         "/var/lib/mysql/{}/mysqlrouter.conf".format(name): services
@@ -301,6 +306,19 @@ class MySQLRouterCharm(charms_openstack.charm.OpenStackCharm):
         cmd = ["systemctl", "enable", self.name]
         subprocess.check_output(cmd, stderr=subprocess.STDOUT)
 
+        # Logrotate File
+        ch_core.templating.render(
+            source="logrotate",
+            template_loader=os_templating.get_loader(
+                "templates/", self.release),
+            target=self.logrotate_file,
+            context={
+                "owner": self.mysqlrouter_user,
+                "group": self.mysqlrouter_group
+            },
+            perms=0o644,
+        )
+
     def get_db_helper(self):
         """Get an instance of the MySQLDB8Helper class.
 

src/templates/logrotate

@@ -0,0 +1,9 @@
+/var/lib/mysql/*/log/*.log {
+	rotate 9
+	notifempty
+	size 10M
+	create 0644 {{ owner }} {{ group }}
+	postrotate
+	kill -HUP $(pidof mysqlrouter)
+	endscript
+}

unit_tests/test_lib_charm_openstack_mysql_router.py

@@ -268,7 +268,7 @@ class TestMySQLRouterCharm(test_utils.PatchHelper):
         self.mkdir.assert_called_once_with(
             "/var/lib/mysql", group="mysql", owner="mysql", perms=0o755)
 
-        self.render.assert_called_once()
+        self.assertEqual(self.render.call_count, 2)
         self.subprocess.check_output.assert_called_once_with(
             ['systemctl', 'enable', _name],
             stderr=self.subprocess.STDOUT)