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Date: Wed, 29 May 2013 13:53:21 +0000 (UTC)
From: "3l3ph4n1n3 (JIRA)" <jira@apache.org>
To: dev@curator.incubator.apache.org
Message-ID: <JIRA.12649612.1369707969451.34786.1369835601794@arcas>
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Subject: [jira] [Commented] (CURATOR-28) Add Expiry Time To
 InterProcessLocks
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    [ https://issues.apache.org/jira/browse/CURATOR-28?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13669262#comment-13669262 ] 

3l3ph4n1n3 commented on CURATOR-28:
-----------------------------------

The client is not necessarily burdened - the situation I described above (the lockTimer thread had a bug in it and crashed, or deadlocked itself with another thread) could happen regardless of the load on the client. The problem I'm trying to avoid is where the heartbeat thread is making progress but the unlocking thread isn't...
                
> 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
>            Priority: Minor
>
> 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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