ActiveRecord::StatementInvalid: Mysql2::Error: closed MySQL connection

I recently experienced the error ActiveRecord::StatementInvalid: Mysql2::Error: closed MySQL connection. Apparently this happens when there is a timeout during query execution. In order to fix this you can reconnect to your db.

Therefore either add reconnect: true to your database.yml for automatic reconnection when the error occurs or catch the error and manually and reconnect explicitly via ActiveRecord::Base.connection.reconnect!

Be aware that reconnecting will have the following impact on your current connection:

Any active transactions are rolled back and autocommit mode is reset.
All table locks are released.
All TEMPORARY tables are closed (and dropped).
...

For further details see the mysql doc Show archive.org snapshot .

You can actually force this error by setting a short timeout and sleeping in the query:

Timeout.timeout(1) { User.find_by_sql('SELECT sleep(2) FROM users;') }
# All subsequent queries then will fail with the error mentioned above
User.count

Andreas Robecke

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Over 10 years ago

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Posted by Andreas Robecke to makandra dev (2013-10-01 11:23)

ActiveRecord::StatementInvalid: Mysql2::Error: closed MySQL connection

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