Change mysql socket path to a persistent path.

This patch changes the default socket patch on the host from
"/var/run/mysqld" to "/var/lib/mysqld". ensuring that the
database container starts properly after a Nova instance is restarted.

Story: 2010599
Task: 47471

Change-Id: Idb0366ad1d73c85126e18fccd58f1e52176b63de

releasenotes/notes/fix-server-restart-bug-9746b2c2ed00a45a.yaml

@@ -0,0 +1,7 @@
+---
+
+fixes:
+  - |
+    Fix a bug where the mysql container is unable to recover
+    after a reboot of the Nova instance.
+    `Story 2010599 <https://storyboard.openstack.org/#!/story/2010599>`__

trove/common/constants.py

@@ -18,3 +18,4 @@ ETH1_CONFIG_PATH = "/etc/trove/eth1.json"
 DOCKER_NETWORK_NAME = "database-network"
 DOCKER_HOST_NIC_MODE = "docker-hostnic"
 DOCKER_BRIDGE_MODE = "bridge"
+MYSQL_HOST_SOCKET_PATH = "/var/lib/mysqld"

trove/guestagent/datastore/mysql_common/manager.py

@@ -21,6 +21,7 @@ from oslo_log import log as logging
 
 from trove.common import cfg
 from trove.common import configurations
+from trove.common import constants
 from trove.common import exception
 from trove.common.notification import EndNotification
 from trove.common import utils
@@ -115,7 +116,8 @@ class MySqlManager(manager.Manager):
             # Set /var/run/mysqld to allow localhost access.
             volumes_mapping = {
                 '/var/lib/mysql': {'bind': '/var/lib/mysql', 'mode': 'rw'},
-                "/var/run/mysqld": {"bind": "/var/run/mysqld", "mode": "ro"},
+                constants.MYSQL_HOST_SOCKET_PATH: {"bind": "/var/run/mysqld",
+                                                   "mode": "ro"},
                 '/tmp': {'bind': '/tmp', 'mode': 'rw'}
             }
             self.app.create_backup(context, backup_info,

trove/guestagent/datastore/mysql_common/service.py

@@ -44,8 +44,9 @@ from trove.instance import service_status
 LOG = logging.getLogger(__name__)
 CONF = cfg.CONF
 ADMIN_USER_NAME = "os_admin"
-CONNECTION_STR_FORMAT = ("mysql+pymysql://%s:%s@localhost/?"
-                         "unix_socket=/var/run/mysqld/mysqld.sock")
+CONNECTION_STR_FORMAT = ("mysql+pymysql://%s:%s@localhost/?" +
+                         f"unix_socket={constants.MYSQL_HOST_SOCKET_PATH}"
+                         "/mysqld.sock")
 ENGINE = None
 INCLUDE_MARKER_OPERATORS = {
     True: ">=",
@@ -590,7 +591,7 @@ class BaseMySqlApp(service.BaseDbApp):
         user = "%s:%s" % (CONF.database_service_uid, CONF.database_service_uid)
 
         # Create folders for mysql on localhost
-        for folder in ['/etc/mysql', '/var/run/mysqld',
+        for folder in ['/etc/mysql', constants.MYSQL_HOST_SOCKET_PATH,
                        '/etc/mysql/mysql.conf.d']:
             operating_system.ensure_directory(
                 folder, user=CONF.database_service_uid,
@@ -599,8 +600,8 @@ class BaseMySqlApp(service.BaseDbApp):
 
         volumes = {
             "/etc/mysql": {"bind": "/etc/mysql", "mode": "rw"},
-            "/var/run/mysqld": {"bind": "/var/run/mysqld",
-                                "mode": "rw"},
+            constants.MYSQL_HOST_SOCKET_PATH: {"bind": "/var/run/mysqld",
+                                               "mode": "rw"},
             "/var/lib/mysql": {"bind": "/var/lib/mysql", "mode": "rw"},
         }
         if extra_volumes:
@@ -671,7 +672,7 @@ class BaseMySqlApp(service.BaseDbApp):
         LOG.info("Restarting mysql")
 
         # Ensure folders permission for database.
-        for folder in ['/etc/mysql', '/var/run/mysqld',
+        for folder in ['/etc/mysql', constants.MYSQL_HOST_SOCKET_PATH,
                        '/etc/mysql/mysql.conf.d']:
             operating_system.ensure_directory(
                 folder, user=CONF.database_service_uid,

trove/guestagent/strategies/replication/mysql_base.py

@@ -95,7 +95,8 @@ class MysqlReplicationBase(base.Replication):
 
         volumes_mapping = {
             '/var/lib/mysql': {'bind': '/var/lib/mysql', 'mode': 'rw'},
-            "/var/run/mysqld": {"bind": "/var/run/mysqld", "mode": "ro"},
+            constants.MYSQL_HOST_SOCKET_PATH: {"bind": "/var/run/mysqld",
+                                               "mode": "ro"},
             '/tmp': {'bind': '/tmp', 'mode': 'rw'}
         }
         service.create_backup(context, snapshot_info,