Reconnecting MySQL Clients with MySQLdb

In the realm of database connectivity, maintaining a persistent connection is crucial for uninterrupted data access. MySQLdb, a popular Python library for interfacing with MySQL databases, provides a way to automatically reconnect clients in case of connection failures.

Enabling Auto-Reconnect in Previous Versions

In earlier versions of MySQLdb, the auto-reconnect functionality could be activated through the mysql_options() function, as shown below:

my_bool reconnect = 1
mysql_options(&mysql, MYSQL_OPT_RECONNECT, &reconnect)

However, with the advent of MySQL Connector/Python, the underlying implementation has changed, and this approach is no longer applicable.

Solution for MySQL Connector/Python

To achieve auto-reconnection in MySQL Connector/Python, it is necessary to customize the Cursor object's behavior. The following code snippet demonstrates this approach:

import MySQLdb

class DB:
  conn = None

  def connect(self):
    self.conn = MySQLdb.connect()

  def query(self, sql):
    try:
      cursor = self.conn.cursor()
      cursor.execute(sql)
    except (AttributeError, MySQLdb.OperationalError):
      self.connect()
      cursor = self.conn.cursor()
      cursor.execute(sql)
    return cursor

db = DB()
sql = "SELECT * FROM foo"
cur = db.query(sql)
# wait a long time for the Mysql connection to timeout
cur = db.query(sql)
# still works

Explanation

This code defines a custom query() method that wraps the Cursor.execute() method. If a connection error occurs (either an AttributeError or MySQLdb.OperationalError), the query() method will attempt to reconnect to the database and then re-execute the query.

By implementing this auto-reconnection mechanism within the Cursor object, you can ensure that your Python scripts can continue to operate even if the MySQL connection is intermittently lost. This approach provides a more robust and reliable means of maintaining database connectivity.