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  1. Moodle
  2. MDL-77852

Cache locks might never release

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    • Icon: Bug Bug
    • Resolution: Unresolved
    • Icon: Minor Minor
    • None
    • 4.1.2
    • Caching
    • MOODLE_401_STABLE

      The current cache lock implementation makes it easy for programmers to make mistakes. If there is an exception between acquire_lock and release_lock (and release_lock is not put into a finally block), the lock might never release. For example, look at \course_modinfo::purge_course_module_cache for such a mistake. However, there may be other reasons (crashes) why a process has not released a lock.

      cachelock_file already supports a maximum lifetime for a lock file, but this is disabled by default.

      Besides cache locks, Moodle also has another locking mechanism (\core\lock\lock_factory), which has a better implementation. get_lock has to return a \core\lock\lock instance, which ensures that the lock is released when the lock object is destructed. And because \core\lock\file_lock_factory::get_lock relies on flock (not just file existence), locks should always be released when a PHP script ends.

            Unassigned Unassigned
            mgauk Martin Gauk
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            9 Vote for this issue
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              Created:
              Updated:

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