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  1. Moodle
  2. MDL-50909

MDL-49489 Causes severe performance degradation of course index and search pages

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    • Icon: Bug Bug
    • Resolution: Deferred
    • Icon: Major Major
    • None
    • 2.7.9
    • Caching
    • Moodle 2.7.9, Ubuntu, MySQL 5.6, PHP 5.5.9, cachstore_memcachecluster, 2 external servers with memcached
    • MySQL
    • MOODLE_27_STABLE
    • Hide
      1. Edit lib/coursecatlib.php, change CACHE_COURSE_CONTACTS_TTL to 1 second (so you don't have to keep waiting around)
      2. Create a new course
      3. On course/search.php search for that course so it shows up, should have no teachers listed
      4. Add a teacher
      5. Search again, the new teacher should be shown
      6. Add another teacher
      7. Search again, the new teacher should be shown
      8. Remove a teacher
      9. Search again, that teacher should disappear
      10. Remove the last teacher
      11. Search again, that teacher should disappear
      Show
      Edit lib/coursecatlib.php , change CACHE_COURSE_CONTACTS_TTL to 1 second (so you don't have to keep waiting around) Create a new course On course/search.php search for that course so it shows up, should have no teachers listed Add a teacher Search again, the new teacher should be shown Add another teacher Search again, the new teacher should be shown Remove a teacher Search again, that teacher should disappear Remove the last teacher Search again, that teacher should disappear

      We have just upgraded from Moodle 2.6 to Moodle 2.7

      The change in MDL-49489 which changed a purge into a delete_many is causing us to have very slow page loads on the course index and course search pages (greater than 60 seconds) when the cache is cleaned.

      While this is affecting us on the memcachecluster plugin it will similarly affect the core memcache and memcached plugins.

      I imagine it is likely to affect 2.8 and greater as well, unless the way delete_many has been changed in them.

      On the search page we are getting an average of 18900 memcache deletes per page load taking on average 13,100 ms.

      On the course index page it is 12900 delete calls per page load taking on average 9,010 ms.

      The purge was actually quite fast for us.

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        3. course-search-page.JPG
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        4. partial_stack_trace_of_slowness-index.jpg
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        5. partial_stack_trace_of_slowness-search.jpg
          partial_stack_trace_of_slowness-search.jpg
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            nmagill Neill Magill
            nmagill Neill Magill
            Damyon Wiese Damyon Wiese
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              Created:
              Updated:
              Resolved:

                Error rendering 'clockify-timesheets-time-tracking-reports:timer-sidebar'. Please contact your Jira administrators.