Greetings Monks!

I have a script that runs often, is run by lots of different processes, and takes a long time. It is basically testing the environment to see if whatever called it can proceed.

I should be able to cache the results in some way, but I want to make sure I do the caching properly.

There is no "Key" for this cache. All answers are the same. A database is not appropriate, so I need to handle any atomic/concurrency stuff.

  1. If the cache is fresh, read it and go away
  2. If the cache is stale...
    1. Try to get exclusive lock
      1. Got lock? Do tests, write results to cache, go away
      2. Didn't get lock????

This is where it gets more complicated. Do I wait around for whoever has the lock to finish? Do I wait only if the locking process is doing the tests? How do I handle a situation where a locking process has wandered off into oblivion and hasn't released the lock?

I'm on linux and I'm thinking with flock, but I'm open to non-flock ideas.

In reply to Concurrent Cache Pattern by pileofrogs

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