Do not RESTART after configure_instance

After the mysql-shell update to 8.0.22 the shell.run_sql("RESTART") in
configure_instance began exiting with non-zero and an error message
stating the MySQL server has gone away.

It seems the shell.run_sql("RESTART") is not necessary. This change
removes this from the configure_instance method. It also adds a
restart_instance method in case we need it in the future.

Closes-Bug: #1901771
Change-Id: I5f5278a4097e75c1a37e1880b594a1e81691249b

src/lib/charm/openstack/mysql_innodb_cluster.py

@@ -571,8 +571,6 @@ class MySQLInnoDBClusterCharm(charms_openstack.charm.OpenStackCharm):
                             .format(address), "INFO")
         _script = (
             "dba.configure_instance('{user}:{pw}@{addr}')\n"
-            "myshell = shell.connect('{user}:{pw}@{addr}')\n"
-            "myshell.run_sql('RESTART;')"
             .format(
                 user=self.cluster_user,
                 pw=self.cluster_password,
@@ -724,6 +722,47 @@ class MySQLInnoDBClusterCharm(charms_openstack.charm.OpenStackCharm):
         leadership.leader_set({"cluster-instance-clustered-{}"
                                .format(address): True})
 
+    def restart_instance(self, address):
+        """Restart instance
+
+        :param self: Self
+        :type self: MySQLInnoDBClusterCharm instance
+        :param address: Address of the MySQL instance to be configured
+        :type address: str
+        :side effect: Calls self.run_mysqlsh_script
+        :returns: This function is called for its side effect
+        :rtype: None
+        """
+        ch_core.hookenv.log("Restarting instance: {}.".format(address), "INFO")
+        _server_gone_away_error = "MySQL Error (2006)"
+        _script = (
+            "myshell = shell.connect('{user}:{pw}@{addr}')\n"
+            "myshell.run_sql('RESTART;')"
+            .format(
+                user=self.cluster_user,
+                pw=self.cluster_password,
+                addr=address))
+        try:
+            output = self.run_mysqlsh_script(_script)
+        except subprocess.CalledProcessError as e:
+            # If the shell reports the server went away we expect this
+            # when giving the RESTART command
+            if _server_gone_away_error not in e.stderr.decode("UTF-8"):
+                ch_core.hookenv.log(
+                    "Failed restarting instance {}: {}"
+                    .format(address, e.stderr.decode("UTF-8")), "ERROR")
+                raise e
+
+        # After configuration of the remote instance, the remote instance
+        # restarts mysql. We need to pause here for that to complete.
+        self.wait_until_connectable(username=self.cluster_user,
+                                    password=self.cluster_password,
+                                    address=address)
+
+        ch_core.hookenv.log("Instance restarted {}: {}"
+                            .format(address, output.decode("UTF-8")),
+                            level="DEBUG")
+
     def reboot_cluster_from_complete_outage(self):
         """Reboot cluster from complete outage.
 

unit_tests/test_lib_charm_openstack_mysql_innodb_cluster.py

@@ -509,11 +509,7 @@ class TestMySQLInnoDBClusterCharm(test_utils.PatchHelper):
         midbc.run_mysqlsh_script = mock.MagicMock()
         _script = (
             "dba.configure_instance('{}:{}@{}')\n"
-            "myshell = shell.connect('{}:{}@{}')\n"
-            "myshell.run_sql('RESTART;')"
-            .format(
-                midbc.cluster_user, midbc.cluster_password, _addr,
-                midbc.cluster_user, midbc.cluster_password, _addr))
+            .format(midbc.cluster_user, midbc.cluster_password, _addr))
 
         midbc.configure_instance(_addr)
         self.is_flag_set.assert_called_once_with(
@@ -525,6 +521,28 @@ class TestMySQLInnoDBClusterCharm(test_utils.PatchHelper):
         self.leader_set.assert_called_once_with(
             {"cluster-instance-configured-{}".format(_addr): True})
 
+    def test_restart_instance(self):
+        _pass = "clusterpass"
+        _addr = "10.10.30.30"
+        self.data = {"cluster-password": _pass}
+        self.is_flag_set.return_value = False
+
+        midbc = mysql_innodb_cluster.MySQLInnoDBClusterCharm()
+        midbc._get_password = mock.MagicMock()
+        midbc._get_password.side_effect = self._fake_data
+        midbc.wait_until_connectable = mock.MagicMock()
+        midbc.run_mysqlsh_script = mock.MagicMock()
+        _script = (
+            "myshell = shell.connect('{}:{}@{}')\n"
+            "myshell.run_sql('RESTART;')"
+            .format(midbc.cluster_user, midbc.cluster_password, _addr))
+
+        midbc.restart_instance(_addr)
+        midbc.run_mysqlsh_script.assert_called_once_with(_script)
+        midbc.wait_until_connectable.assert_called_once_with(
+            address=_addr, username=midbc.cluster_user,
+            password=midbc.cluster_password)
+
     def test_create_cluster(self):
         _pass = "clusterpass"
         _addr = "10.10.40.40"