How to do distributed locking (2016)

I suggest reading the comment I left back then in this blog post comments section, and the reply I wrote in my blog.

Btw, things to note in random order:

1. Check my comment under this blog post. The author had missed a fundamental point in how the algorithm works. Then he based the refusal of the algorithm on the remaining weaker points.

2. It is not true that you can't wait an approximately correct amount of time, with modern computers an APIs. GC pauses are bound and monotonic clocks work. These are acceptable assumptions.

3. To critique the auto release mechanism in-se, because you don't want to expose yourself to the fact that there is a potential race, is one thing. To critique the algorithm in front of its goals and its system model is another thing.

4. Over the years Redlock was used in a huge amount of use cases with success, because if you pick a timeout which is much larger than: A) the time to complete the task. B) the random pauses you can have in normal operating systems. Race conditions are very hard to trigger, and the other failures in the article were, AFAIK, never been observed. Of course if you have a super small timeout to auto release the lock, and the task may easily take this amount of time, you just committed a deisgn error, but that's not about Redlock.

To be honest I've long been puzzled by your response blog post. Maybe the following question can help achieve common ground:

Would you use RedLock in a situation where the timeout is fairly short (1-2 seconds maybe), the work done usually takes ~90% of that timeout, and the work you do while holding a RedLock lock MUST NOT be done concurrently with another lock holder?

I think the correct answer here is always "No" because the risk of the lease sometimes expiring before the client has finished its work is very high. You must alter your work to be idempotent because RedLock cannot guarantee mutual exclusion under all circumstances. Optimistic locking is a good way to implement this type of thing while the work done is idempotent.