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https://issues.apache.org/jira/browse/CURATOR-14?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13684679#comment-13684679
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Ioannis Canellos commented on CURATOR-14:
-----------------------------------------
Apparently there is something I am missing here :-D
So the main problem is that there is no way to clear a Watcher that has been
assigned to ZooKeeper.
Eventually this can lead to a memory leak since its not possible to garbage
collect Watcher instances.
In order to workaround this problem we should limit the amount of Watchers we
create and reuse Watcher instances when its possible.
Currently curator is using Guava's cache that uses "weak values" so that values
can be garbage collected (once they are weakly reachable). This is done
transparently whenever we call usingWatcher via Watching.
There are a couple of things that I don't understand here:
i) If using "guava's cache" was enough, then what is to be implemented for this
issue? The cache is already in place and is already being used in a transparent
way.
ii) Does the garbage collector ever manage to collect values of the cache,
given that they are not cleared in ZooKeeper? From some tests I run using a
modified version of the attached MemoryTest I don't see any value getting
garbage collected.
> Memory leak in Curator watches
> ------------------------------
>
> Key: CURATOR-14
> URL: https://issues.apache.org/jira/browse/CURATOR-14
> Project: Apache Curator
> Issue Type: New Feature
> Components: Recipes
> Affects Versions: 2.0.0-incubating
> Reporter: Brandon Beck
> Priority: Minor
> Attachments: CURATOR-14-draft-2.patch, CURATOR-14-draft-3.patch,
> CURATOR-14.patch, MemoryTest.java
>
>
> The JVM runs out of memory if you repetitively create a PathChildrenCache,
> start it then immediately stop it. It appears that the memory is taken up by
> a watch that isn't ever cleaned up. Curator attempts to do some pooling of
> watches, but doesn't seem to use the path in the pooling.
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