Use MySQL protocol-level ping.

Utilizes MySQL protocol-level pings for disconnection detection.
This is just a 5-byte packet followed by a 7-byte response.

Affects MySQLdb, MySQL Connector and PyMySQL dialects.

Change-Id: I672f75e3746878d88987a31750444dde0cf8eb9b
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/460

3 files changed, 32 insertions, 1 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/mysqlconnector.py b/lib/sqlalchemy/dialects/mysql/mysqlconnector.py
index 1ead8aaf5..e16b68bad 100644
--- a/lib/sqlalchemy/dialects/mysql/mysqlconnector.py
+++ b/lib/sqlalchemy/dialects/mysql/mysqlconnector.py
@@ -160,6 +160,17 @@ class MySQLDialect_mysqlconnector(MySQLDialect):
         from mysql import connector
         return connector
 
+    def do_ping(self, dbapi_connection):
+        try:
+            dbapi_connection.ping(False)
+        except self.dbapi.Error as err:
+            if self.is_disconnect(err, dbapi_connection, None):
+                return False
+            else:
+                raise
+        else:
+            return True
+
     def create_connect_args(self, url):
         opts = url.translate_connect_args(username='user')
 
@@ -225,7 +236,8 @@ class MySQLDialect_mysqlconnector(MySQLDialect):
         exceptions = (self.dbapi.OperationalError, self.dbapi.InterfaceError)
         if isinstance(e, exceptions):
             return e.errno in errnos or \
-                "MySQL Connection not available." in str(e)
+                "MySQL Connection not available." in str(e) or \
+                "Connection to MySQL is not available" in str(e)
         else:
             return False
 
diff --git a/lib/sqlalchemy/dialects/mysql/mysqldb.py b/lib/sqlalchemy/dialects/mysql/mysqldb.py
index 535c8ec52..7554d244c 100644
--- a/lib/sqlalchemy/dialects/mysql/mysqldb.py
+++ b/lib/sqlalchemy/dialects/mysql/mysqldb.py
@@ -101,6 +101,17 @@ class MySQLDialect_mysqldb(MySQLDialect):
     def dbapi(cls):
         return __import__('MySQLdb')
 
+    def do_ping(self, dbapi_connection):
+        try:
+            dbapi_connection.ping(False)
+        except self.dbapi.Error as err:
+            if self.is_disconnect(err, dbapi_connection, None):
+                return False
+            else:
+                raise
+        else:
+            return True
+
     def do_executemany(self, cursor, statement, parameters, context=None):
         rowcount = cursor.executemany(statement, parameters)
         if context is not None:
diff --git a/lib/sqlalchemy/dialects/mysql/pymysql.py b/lib/sqlalchemy/dialects/mysql/pymysql.py
index 4f1c792f9..5f176cef2 100644
--- a/lib/sqlalchemy/dialects/mysql/pymysql.py
+++ b/lib/sqlalchemy/dialects/mysql/pymysql.py
@@ -61,6 +61,14 @@ class MySQLDialect_pymysql(MySQLDialect_mysqldb):
     def dbapi(cls):
         return __import__('pymysql')
 
+    def is_disconnect(self, e, connection, cursor):
+        if super(MySQLDialect_pymysql, self).is_disconnect(e, connection, cursor):
+            return True
+        elif isinstance(e, self.dbapi.Error):
+            return "Already closed" in str(e)
+        else:
+            return False
+
     if py3k:
         def _extract_error_code(self, exception):
             if isinstance(exception.args[0], Exception):