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From "3l3ph4n1n3 (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CURATOR-28) Add Expiry Time To InterProcessLocks
Date Tue, 28 May 2013 02:27:19 GMT
3l3ph4n1n3 created CURATOR-28:
---------------------------------

             Summary: Add Expiry Time To InterProcessLocks
                 Key: CURATOR-28
                 URL: https://issues.apache.org/jira/browse/CURATOR-28
             Project: Apache Curator
          Issue Type: New Feature
          Components: Recipes
    Affects Versions: 2.0.0-incubating
            Reporter: 3l3ph4n1n3
            Assignee: Jordan Zimmerman


If a client takes a distributed lock and fails without breaking its zookeeper connection (e.g.
the main application thread deadlocks) then that lock will never be released (at least without
manual intervention, e.g. killing the process that has it). When a client's acquiring a lock
I'd like to be able to specify a time after which the lock is automatically released. If the
client currently holds the lock it should be able to extend this time period as many times
as it likes. A write-up for what I'm describing for redis is here: https://chris-lamb.co.uk/posts/distributing-locking-python-and-redis
.

I can see a couple of ways of going about this - the lock lifetime could be stored in the
node's date (and so clients could check if the node had expired by adding the lifetime to
the node's ctime or mtime). However, comparing the client's current time with the expiry time
in the node is probably not the right thing to do as the client's clock may be out of sync
with the other clients (or the zookeeper nodes). It'd be nice if zookeeper could automatically
delete nodes (i.e. release the lock) after a certain amount of time - i.e. make it the zookeeper
cluster's decision when the lock is expired, not the client's decision. However, I'm not sure
exactly how to do this...

Thanks,

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