Django - OperationalError: (2006, 'MySQL server has gone away')

Question

Bottom line first: How do you refresh the MySQL connection in django?

Following a MySQL server has gone away error I found that MySQL docum

Answer 1

The idea of the solution is clear: reconnect to mysql if the current connection is broken.

Please check this out:

def make_sure_mysql_usable():
    from django.db import connection, connections
    # mysql is lazily connected to in django.
    # connection.connection is None means
    # you have not connected to mysql before
    if connection.connection and not connection.is_usable():
        # destroy the default mysql connection
        # after this line, when you use ORM methods
        # django will reconnect to the default mysql
        del connections._connections.default

Answer 2

The main reason that leads to this exception is mostly due to client ideal longer than wait_timeout on mysql server.

In order to prevent that kind of error, django supports an option named CONN_MAX_AGE which allow django to recreate new connection if old connections are ideal too long. So you should make sure that CONN_MAX_AGE value is smaller than wait_timout value.

One important thing is that, django with wsgi handles checking CONN_MAX_AGE every requests by calling close_old_connections. So you mainly don't need to care about that. However if you are using django in standard alone application, there is no trigger to run that function. So you have to call it manually. So let call close_old_connections in your code base.

Note: close_old_connections will keep old connections if they're not expired yet. Your connections are still reused in case of high frequency query.

Answer 3

Since Django 1.6, you can use

import django.db

django.db.close_old_connections()

This does basically the same thing as adamsmith's answer except that it handles multiple databases and also honors the CONN_MAX_AGE setting. Django calls close_old_connections() automatically before and after each request, so you normally don't have to worry about it unless you have some long-running code outside of the normal request/response cycle.

Answer 4

having the same issue. I need idea how to check connection state for MySQLdb connection in django. i guess it can be achieved by

try:
    cursor.execute(sql)
catch OperationalError:
    reconnect

is anybody have a better idea?

UPDATE

my decision

self.connection.stat()
if self.connection.errno()!=0:

check state of mysqldb connection if error recreate connection

UPDATE AGAIN

you also need to serve case if connection is close

if self.connection.open:
    self.connection.stat()

refresh connection is just recreating it

    db_settings = settings.DATABASES['mysql_db']
    try:
        self.connection = MySQLdb.connect(host=db_settings['HOST'],port=int(db_settings['PORT']),db=db_settings['NAME'],user=db_settings['USER'],passwd=db_settings['PASSWORD'])
    except MySQLdb.OperationalError, e:
        self.connection = None