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  1. Moodle
  2. MDL-65941

Redis server issues break cache configuration page



    • Type: Bug
    • Status: Waiting for peer review
    • Priority: Minor
    • Resolution: Unresolved
    • Affects Version/s: 3.6.4, 3.7
    • Fix Version/s: None
    • Component/s: Caching
    • Labels:


      If you have an instance of the redis cache store, and Moodle is unable to connect to the redis server, the cache configuration page fails with an exception. This is unlike the behaviour of other stores, like memcached, where the instance is simply marked as "not ready" if the server can't be contacted.

      This is potentially a pretty serious issue for server administrators as it makes it impossible to switch to another cache store while a redis server is unavailable.

      To reproduce (with a working redis server):

      1. Create a redis cache instance. Confirm that it shows as "ready".
      2. Kill the redis server (either kill the process, or the container)
      3. Go back to the cache page.
      4. You will see an error message (either "Connection refused" or "getaddrinfo failed" depending on what you did in step 2) and be unable to edit your cache configuration.

      I'm seeing this with versions 4.1.1 and 4.3.0 of the redis plugin.




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