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From Jordan Zimmerman <jor...@jordanzimmerman.com>
Subject Re: WriteLock does not work.
Date Sun, 15 Dec 2013 14:08:35 GMT
Are you using a JVM language? Curator already has a revocable lock recipe.

http://curator.apache.org/apidocs/org/apache/curator/framework/recipes/locks/InterProcessMutex.html

-Jordan

On Dec 15, 2013, at 8:28 AM, mdzfirst mdzfirst <mdzfirst@gmail.com> wrote:

> Hi everyone,
> 
> I would like to implement a 'preemptible' mutex with the WriteLock example
> in the recipe. My method is like this.
> 
> 1. Acquire the WriteLock and get the resources
> 2. Set a watch on the lock's root node with getChildren() repeatedly, using
> a separate ZooKeeper client
> 3. If only one child (self) is found, sleep
> 4. The callback function only wakes up the main thread
> 5. If the watch is triggered and > 1 children are found, release the
> resources and unlock the WriteLock
> 
> In my design, I will execute the jar multiple times. Each time a new one is
> started, the old one should be forced to release the mutex. It works. The
> first execution does stop. However, the second process seems to lose its
> watch on the first one, because the callback function I passed to the
> WriteLock object is never evoked. The callback function is used to
> synchronize the locking request and is thus very important.
> 
> Can anyone see any flaws in my design, or provide a different way that
> works? Thanks~
> 
> Best regards,
> mdzfirst


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