Does gearmand with libdrizzle work while mysql-database is down for a while?

Question

Use-Case:

• The gearmand is fully operational with libdrizzle as persistence-layer to a mysql-database
• The drizzle connection crashes (e.g. the gearmand-database is locked for some minutes during nightly backups, or the mysql server crashes or network-problems to the database-server).

Question:

Does the gearmand work without the persistence in this moment (MySQL) and catch up later?

Answer 1

Answer

No.

Details

• Debian 6
• gearmand 1.1.8 (via https://launchpad.net/gearmand)
• exactly 5000 jobs to be created via doBackground
• persist the jobs into mysql

/usr/local/sbin/gearmand -q mysql --mysql-user user1 --mysql-password pass1 --mysql-db gearmand

Scenario #1

Scenario:

• Enable READ lock for gearman queue table

Result:

• The script, which creates the background tasks, is on hold.
• After removing the READ lock, the script continues and creates all 5000 jobs successfully.
• Note: I just tested the lock for some seconds. The script might crash due to a timeout.

Scenario #2

Scenario:

• Stop the entire mysql server instance (with the gearman queue)

Result:

• Without the mysqld, the jobs cannot be created.
• 3974 jobs out of 5000 have been created.

• gearmand output:

  mysql_stmt_prepare failed: Can't connect to local MySQL server through socket X

• PHP script output:

  PHP Warning: GearmanClient::doBackground(): gearman_client_run_tasks:QUEUE_ERROR:QUEUE_ERROR

Unfortunately, with my test scenarios, the gearmand stops work if the mysql persistence layer is unavailable.