Add option to use a fresh connection for mysql cache

changelog/63991.fixed.md

@@ -0,0 +1 @@
+Added option to use a fresh connection for mysql cache

salt/cache/mysql_cache.py

@@ -33,6 +33,8 @@ could be set in the master config. These are the defaults:
     mysql.password: None
     mysql.database: salt_cache
     mysql.table_name: cache
+    # This may be enabled to create a fresh connection on every call
+    mysql.fresh_connection: false
 
 Related docs can be found in the `python-mysql documentation`_.
 
@@ -63,10 +65,17 @@ try:
     import MySQLdb.converters
     import MySQLdb.cursors
     from MySQLdb.connections import OperationalError
+
+    # Define the interface error as a subclass of exception
+    # It will never be thrown/used, it is defined to support the pymysql error below
+    class InterfaceError(Exception):
+        pass
+
 except ImportError:
     try:
         # MySQLdb import failed, try to import PyMySQL
         import pymysql
+        from pymysql.err import InterfaceError
 
         pymysql.install_as_MySQLdb()
         import MySQLdb
@@ -109,8 +118,12 @@ def run_query(conn, query, args=None, retries=3):
     Get a cursor and run a query. Reconnect up to ``retries`` times if
     needed.
     Returns: cursor, affected rows counter
-    Raises: SaltCacheError, AttributeError, OperationalError
+    Raises: SaltCacheError, AttributeError, OperationalError, InterfaceError
     """
+    if __context__.get("mysql_fresh_connection"):
+        # Create a new connection if configured
+        conn = MySQLdb.connect(**__context__["mysql_kwargs"])
+        __context__["mysql_client"] = conn
     if conn is None:
         conn = __context__.get("mysql_client")
     try:
@@ -124,7 +137,7 @@ def run_query(conn, query, args=None, retries=3):
             out = cur.execute(query, args)
 
         return cur, out
-    except (AttributeError, OperationalError) as e:
+    except (AttributeError, OperationalError, InterfaceError) as e:
         if retries == 0:
             raise
         # reconnect creating new client
@@ -144,9 +157,7 @@ def run_query(conn, query, args=None, retries=3):
         if len(query) > 150:
             query = query[:150] + "<...>"
         raise SaltCacheError(
-            "Error running {}{}: {}".format(
-                query, "- args: {}".format(args) if args else "", e
-            )
+            "Error running {}{}: {}".format(query, f"- args: {args}" if args else "", e)
         )
 
 
@@ -232,6 +243,7 @@ def _init_client():
     mysql_kwargs["autocommit"] = True
 
     __context__["mysql_table_name"] = opts.pop("mysql.table_name", "salt")
+    __context__["mysql_fresh_connection"] = opts.pop("mysql.fresh_connection", False)
 
     # Gather up any additional MySQL configuration options
     for k in opts:
@@ -266,7 +278,7 @@ def store(bank, key, data):
     cur, cnt = run_query(__context__.get("mysql_client"), query, args=args)
     cur.close()
     if cnt not in (1, 2):
-        raise SaltCacheError("Error storing {} {} returned {}".format(bank, key, cnt))
+        raise SaltCacheError(f"Error storing {bank} {key} returned {cnt}")
 
 
 def fetch(bank, key):
@@ -297,7 +309,7 @@ def flush(bank, key=None):
         data = (bank, key)
         query += " AND etcd_key=%s"
 
-    cur, _ = run_query(__context__["mysql_client"], query, args=data)
+    cur, _ = run_query(__context__.get("mysql_client"), query, args=data)
     cur.close()
 
 
@@ -348,7 +360,7 @@ def updated(bank, key):
         "AND etcd_key=%s".format(__context__["mysql_table_name"])
     )
     data = (bank, key)
-    cur, _ = run_query(__context__["mysql_client"], query=query, args=data)
+    cur, _ = run_query(__context__.get("mysql_client"), query=query, args=data)
     r = cur.fetchone()
     cur.close()
     return int(r[0]) if r else r

tests/pytests/unit/cache/test_mysql_cache.py

@@ -170,6 +170,7 @@ def test_init_client():
             assert (
                 mysql_cache.__context__["mysql_kwargs"]["max_allowed_packet"] == 100000
             )
+            assert not mysql_cache.__context__["mysql_fresh_connection"]
 
     with patch.dict(
         mysql_cache.__opts__,
@@ -177,6 +178,7 @@ def test_init_client():
             "mysql.max_allowed_packet": 100000,
             "mysql.db": "salt_mysql_db",
             "mysql.host": "mysql-host",
+            "mysql.fresh_connection": True,
         },
     ):
         with patch.object(mysql_cache, "_create_table") as mock_create_table:
@@ -193,6 +195,7 @@ def test_init_client():
             assert (
                 mysql_cache.__context__["mysql_kwargs"]["max_allowed_packet"] == 100000
             )
+            assert mysql_cache.__context__["mysql_fresh_connection"]
 
 
 def test_create_table():