Against race conditions and duplicate cron entries#10
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- **File Locking**: Uses `flock` to ensure only one update process runs at a time - **Atomic File Operations**: Uses `mv` instead of `cat` for atomic file updates - **Duplicate Prevention**: Tracks processed jobs to prevent duplicate cron entries - **Unique Temp Files**: Uses process-specific temporary files to prevent conflicts - **Proper Cleanup**: Automatic cleanup of temporary files on script exit
vedmaka
requested changes
Jul 8, 2025
| # Use flock to ensure only one update process runs at a time | ||
| ( | ||
| flock -x 9 || { | ||
| log "Another update is already running, skipping this event" |
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This failover won't be triggered unless you provide -n parameter because -x waits for the lock to release by default
But we probably don't want to have this failover in the first place, otherwise it would discard the events after the one that triggred the update so it's possible that the contab ends up in not desired state. Example with this failover in place:
- An event received for labels update
- The update of the crontab started
- Labels updated again shortly until the crontab update is completed
- The last even is discarded and you end up with crontab state not matching the labels
So I would not add -n but instead remove the failover || {...} so it would not confuse anyone looking at it
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Thanks, you are right.
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vedmaka
approved these changes
Jul 9, 2025
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flockto ensure only one update process runs at a timemvinstead ofcatfor atomic file updates