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kenn / redis-mutex

Distributed mutex using Redis
https://rubygems.org/gems/redis-mutex
MIT License
280 stars 44 forks source link

Stalling in non-blocking mode? #30

Open milgner opened 6 years ago

milgner commented 6 years ago

I'm currently investigating a problem where two concurrent jobs are stalling even though I specified block: 0. The basic logic is 

begin
  RedisMutex.with_lock(self.class.to_s, block: 0) do
    # do work
  end
rescue RedisMutex::LockError
  # someone else is already working on it - going home now.
end

So far I have been unable to force a reproduction on my local machine. Do you have an idea what might be the cause? One difference that comes to mind is that the real machine uses a hosted Redis (cluster mode, 1 shard, 2 nodes) versus the local Redis on my dev machine.

kenn commented 6 years ago

You might have hit the issue described in #5 - PR is ready with #27, but I think Redlock would work better for newer versions of Redis. I tried to tweak it to fit the redis-mutex API, but it wasn't a small task. PR would be appreciated.

januszm commented 2 months ago

Not sure if I understand the meaning of the non-blocking mode right, but I recently had a problem where a job was started from cron on servers and lasted less than 1 second (fast task). The job worked on all 3 and did not trigger the LockError error. block=1 looks like some solution to random problems with connecting to Redis, right? have 1 second grace period for estalising the connection and acquiring the lock. This option in practice means that tasks can be executed many times in one second (block=1) if they last shorter.