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  1. Moodle
  2. MDL-45724

Detect the use of same memcached instance for both sessions and muc and warn about it

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Details

    • MOODLE_26_STABLE, MOODLE_27_STABLE
    • MOODLE_26_STABLE, MOODLE_27_STABLE
    • 45724-28
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      1. Prepare a memcache server if you've not already got one up.
      2. Configure Moodle sessions to use memcache (see $CFG->session_memcached_save_path)
      3. Configure a Memcache cache store to use that same memcache server.
      4. Observe that you get a warning on the Cache configuration page about using the same memcache serve for both MUC and sessions.
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      Prepare a memcache server if you've not already got one up. Configure Moodle sessions to use memcache (see $CFG->session_memcached_save_path) Configure a Memcache cache store to use that same memcache server. Observe that you get a warning on the Cache configuration page about using the same memcache serve for both MUC and sessions.

    Description

      Right now it's possible to use the same memcached instance with moodle for both php sessions and muc store.

      memcached implementation has a well-known (MDL-45375) inability to invalidate/purge group of keys, so current implementation simply deletes everything on purge of any cache.

      That can hit php sessions being deleted together with MUC contents, and that can lead to real problems, invalidating moodle sessions in the middle (of a quiz, of a post...).

      So it would be great to articulate some way to detect if the same memcached instance is being used for both php sessions and muc and warn, loud and in red about the risks of such combination.

      Perhaps with a "fixed" key, or comparing settings or whatever. And to be shown in the admin notifications or in environment info or wherever.

      Anything visible enough. Ciao

      Attachments

        Issue Links

          has a non-specific relationship to

          Bug - A problem which impairs or prevents Moodle from functioning correctly. MDL-37145 Documentation for caching admin screens

          • Blocker - Blocks development and/or testing, prevents Moodle from running (applicable to bugs only)
          • Closed

          Improvement - An enhancement to an existing Moodle feature. MDL-45375 Allow multiple MUC instances on one memcached server using cachestore_memcache

          • Critical - Crashes server, loss of data, severe memory leak
          • Closed
          Testing discovered

          Bug - A problem which impairs or prevents Moodle from functioning correctly. MDLSITE-3255 Odd moodlecheck warnings for complete phpdoc

          • Low - Cosmetic problems, nice-to-have features
          • Closed

          Activity

            People

              samhemelryk Sam Hemelryk
              stronk7 Eloy Lafuente (stronk7)
              Tim Hunt Tim Hunt
              Dan Poltawski Dan Poltawski
              David Monllaó David Monllaó
              David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo, Matteo Scaramuccia, David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo
              Votes:
              4 Vote for this issue
              Watchers:
              14 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved:
                8/Sep/14