XF 1 Deadlock Avoidance by Xon MOVED

XenForo's Datawriters have a _postSaveAfterTransaction() method. This method is intended to run after a database transaction is finished, but if a DataWriter is called from with-in another DataWriter, this does not happen.

This incurs the risk that various notification actions will pull in large queries into the transaction, which increasing the risk of deadlocks on a busy forum.

This is a formally private add-on which has been in use for about a month before being released.

This add-on is only for busy forums which sometimes experience deadlocks on the listed conditions. Please test carefully as this add-on may break other add-ons.

This add-on requires php +5.5, and will not work with earlier versions.

• Race condition for watch thread toggle
• Deadlock on conversations
• Deadlock on posts
• Deadlock on resolving/rejecting Reports

Race condition for watch thread toggle

Fixes a race condition when creating/removing a watch thread state

Deadlock on conversations

Provides a workaround for a XenForo design issue where updating conversation counters can cause deadlocks.

• rebuilding user conversation counters occurs inside a large transaction, and is deadlock prone.

Deadlock on posts

Provides a workaround for a XenForo design issue where adding/removing posts can cause deadlocks.

• updating user alert counters occurs inside a large transaction, and is deadlock prone.

Deadlock on resolving/rejecting Reports
Provides a workaround for a XenForo design issue where adding/removing posts can cause deadlocks.

• Sends report resolve/reject alerts inside the transaction.