Fix new scheduled tasks jumping the queue #17962
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richvdh
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Nov 26, 2024
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| # We need to wait for the next run of the scheduler loop | ||
| self.reactor.advance((TaskScheduler.SCHEDULE_INTERVAL_MS / 1000)) |
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this hasn't actually changed, I'm just tightening up the test a bit. We didn't need to wait for the next run of the loop, we just had to wait 0.1 seconds. Looks like this changed in matrix-org/synapse#16313 and matrix-org/synapse#16660 without the test being updated.
Currently, when a new scheduled task is added and its scheduled time has already passed, we set it to ACTIVE. This is problematic, because it means it will jump the queue ahead of all other SCHEDULED tasks; furthermore, if the Synapse process gets restarted, it will jump ahead of any ACTIVE tasks which have been started but are taking a while to run. Instead, we leave it set to SCHEDULED, but kick off a call to `_launch_scheduled_tasks`, which will decide if we actually have capacity to start a new task, and start the newly-added task if so.
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Currently, when a new scheduled task is added and its scheduled time has already passed, we set it to ACTIVE. This is problematic, because it means it will jump the queue ahead of all other SCHEDULED tasks; furthermore, if the Synapse process gets restarted, it will jump ahead of any ACTIVE tasks which have been started but are taking a while to run.
Instead, we leave it set to SCHEDULED, but kick off a call to
_launch_scheduled_tasks, which will decide if we actually have capacity to start a new task, and start the newly-added task if so.