Rewrite the background queue to not use locks for the insertion#6299
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Rewrite the background queue to not use locks for the insertion#6299
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The previous approach used a transaction and a write lock on the unique background jobs. This can cause a deadlock in some situations due to a different ordering of jobs. Further inspection revealed that the transaction only exists for historic reasons to slightly improve the insert performance. The write lock on the job isn’t necessary because at worst the unique job vanishes the moment the job would have been queued which makes no difference. Filtering out any already queued unique job first allows us to use a lock-free approach to insert the jobs. See https://www.woltlab.com/community/thread/311983-could-not-execute-statement-insert-into-wcf1-background-job-job-time-identifier/
BurntimeX
approved these changes
May 20, 2025
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The previous approach used a transaction and a write lock on the unique background jobs. This can cause a deadlock in some situations due to a different ordering of jobs.
Further inspection revealed that the transaction only exists for historic reasons to slightly improve the insert performance. The write lock on the job isn’t necessary because at worst the unique job vanishes the moment the job would have been queued which makes no difference.
Filtering out any already queued unique job first allows us to use a lock-free approach to insert the jobs.
See https://www.woltlab.com/community/thread/311983-could-not-execute-statement-insert-into-wcf1-background-job-job-time-identifier/