Details
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Improvement
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Status: Closed
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Minor
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Resolution: Fixed
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3.9.4, 3.10.1, 3.11, 4.0
Description
Investigating long running `\core_course\task\course_delete_modules` adhoc tasks, it's been found that recycle bin slows down the task:
Execute adhoc task: core_course\task\course_delete_modules
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... started 14:45:17. Current memory use 3.7MB. |
Wed, 03 Mar 2021 14:45:17 +1100 Deleting url |
Wed, 03 Mar 2021 14:45:17 +1100 Calling pre_course_module_delete callback |
Wed, 03 Mar 2021 14:45:17 +1100 Starting backup |
Wed, 03 Mar 2021 14:59:22 +1100 Backup size: 3.6KB |
Wed, 03 Mar 2021 14:59:22 +1100 Deleting questions and question categories |
Wed, 03 Mar 2021 14:59:22 +1100 Calling url_delete_instance function |
Wed, 03 Mar 2021 14:59:22 +1100 Removing all module files in case modules forget to do that |
Wed, 03 Mar 2021 14:59:22 +1100 Removing events from calendar |
Wed, 03 Mar 2021 14:59:22 +1100 Removing grade items |
Wed, 03 Mar 2021 14:59:22 +1100 Removing blogs |
Wed, 03 Mar 2021 14:59:22 +1100 Removing completion and availability data |
Wed, 03 Mar 2021 14:59:22 +1100 Removing all tags |
Wed, 03 Mar 2021 14:59:22 +1100 Calling hook_course_module_deleted |
Wed, 03 Mar 2021 14:59:22 +1100 Deleting the context |
Wed, 03 Mar 2021 14:59:22 +1100 Deleting the module from the course_modules table |
Wed, 03 Mar 2021 14:59:22 +1100 Deleting module from the course section |
Wed, 03 Mar 2021 14:59:22 +1100 Triggering course_module_deleted ervent |
Wed, 03 Mar 2021 14:59:22 +1100 Rebuilding course cache |
Wed, 03 Mar 2021 14:59:22 +1100 Time took to delete url: 845 seconds. |
... used 484 dbqueries |
... used 845.49422883987 seconds |
Adhoc task complete: core_course\task\course_delete_modules
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Profiling showed a bottleneck: `backup_helper::delete_old_backup_dirs` on `drop_and_clean_temp_stuff` step.
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This might happen in large sites with `temp/backup` dir located on NFS and with a big number or files in it (39k in this case). So total time to fetch files in the directory will be NFS latency * number of files.
My proposal is to move `backup_helper::delete_old_backup_dirs` to a dedicated the existing 'backup_cleanup_task' scheduled task and run it once a day (or with any other schedule). I think we don't really need to full scan `temp/backup` directory after each backup/restore. Especially if we have thousands of these tasks per day.
Steps to replicate the issue:
- Emulate filesystem latency by putting `usleep(2000);` here https://github.com/moodle/moodle/blob/95dd305cc6c84b5c6735df9e3506cebb79ac67f9/lib/moodlelib.php#L7044
- Create 50k files in `temp/backup` dir (`touch randomfile{00001..50000}.txt` for linux)
- Enable async backups
- Taka a backup and run adhoc tasks
- Increase latency or number of files and see how the time of adhoc task varies
Attachments
Issue Links
- caused a regression
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MDL-71367 Errors with core_backup_cleanup_task_testcase under Windows
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- Closed
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