problem

In a client instance a task import failed with error message

ERROR in core.entity.editor_Models_Foldertree.editor_Models_Foldertree: E1015 - Duplicate Key on saving editor_Models_Foldertree

triggered by

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '{d605dcc3-0d1f-45b8-8b2b-8d957bcd1c16}' for key 'taskGuid', query was: INSERT INTO `LEK_foldertree` (`tree`, `taskGuid`) VALUES (?, ?)

reason

The reason was, that the worker which produces the folder tree was started twice.

In the most cases this is prevented by worker->isMutexAccess check, but after investigation it came out, that this check is incomplete, since the locking done by the underlying method is not atomic. In isMutexAccess the state and the hash of the worker is checked but only the hash is updated there. The state is set some lines of code later to state running. If a second request tries to start the same worker between isMutexAccess call and setRunning this error can happen.

solution

Evaluate if we can directly set the worker to running in isMutexAccess, but the state must then be rolled back on failure.

additional todos

The indices of the worker table must be optimized to the performed requests, currently there is one index per field.

Also "SET TRANSACTION ISOLATION LEVEL READ COMMITTED" should be added to the ismutexaccess function and to the scheduleprepared call.