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https://issues.apache.org/jira/browse/CASSANDRA-6345?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13821979#comment-13821979
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Jonathan Ellis commented on CASSANDRA-6345:
-------------------------------------------
I have to admit I like it better without the custom wrapper class. :)
> Endpoint cache invalidation causes CPU spike (on vnode rings?)
> --------------------------------------------------------------
>
> Key: CASSANDRA-6345
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6345
> Project: Cassandra
> Issue Type: Bug
> Environment: 30 nodes total, 2 DCs
> Cassandra 1.2.11
> vnodes enabled (256 per node)
> Reporter: Rick Branson
> Assignee: Jonathan Ellis
> Fix For: 1.2.12, 2.0.3
>
> Attachments: 6345-rbranson.txt, 6345-v2.txt, 6345.txt,
> half-way-thru-6345-rbranson-patch-applied.png
>
>
> We've observed that events which cause invalidation of the endpoint cache
> (update keyspace, add/remove nodes, etc) in AbstractReplicationStrategy
> result in several seconds of thundering herd behavior on the entire cluster.
> A thread dump shows over a hundred threads (I stopped counting at that point)
> with a backtrace like this:
> at java.net.Inet4Address.getAddress(Inet4Address.java:288)
> at
> org.apache.cassandra.locator.TokenMetadata$1.compare(TokenMetadata.java:106)
> at
> org.apache.cassandra.locator.TokenMetadata$1.compare(TokenMetadata.java:103)
> at java.util.TreeMap.getEntryUsingComparator(TreeMap.java:351)
> at java.util.TreeMap.getEntry(TreeMap.java:322)
> at java.util.TreeMap.get(TreeMap.java:255)
> at
> com.google.common.collect.AbstractMultimap.put(AbstractMultimap.java:200)
> at
> com.google.common.collect.AbstractSetMultimap.put(AbstractSetMultimap.java:117)
> at com.google.common.collect.TreeMultimap.put(TreeMultimap.java:74)
> at
> com.google.common.collect.AbstractMultimap.putAll(AbstractMultimap.java:273)
> at com.google.common.collect.TreeMultimap.putAll(TreeMultimap.java:74)
> at
> org.apache.cassandra.utils.SortedBiMultiValMap.create(SortedBiMultiValMap.java:60)
> at
> org.apache.cassandra.locator.TokenMetadata.cloneOnlyTokenMap(TokenMetadata.java:598)
> at
> org.apache.cassandra.locator.AbstractReplicationStrategy.getNaturalEndpoints(AbstractReplicationStrategy.java:104)
> at
> org.apache.cassandra.service.StorageService.getNaturalEndpoints(StorageService.java:2671)
> at
> org.apache.cassandra.service.StorageProxy.performWrite(StorageProxy.java:375)
> It looks like there's a large amount of cost in the
> TokenMetadata.cloneOnlyTokenMap that
> AbstractReplicationStrategy.getNaturalEndpoints is calling each time there is
> a cache miss for an endpoint. It seems as if this would only impact clusters
> with large numbers of tokens, so it's probably a vnodes-only issue.
> Proposal: In AbstractReplicationStrategy.getNaturalEndpoints(), cache the
> cloned TokenMetadata instance returned by TokenMetadata.cloneOnlyTokenMap(),
> wrapping it with a lock to prevent stampedes, and clearing it in
> clearEndpointCache(). Thoughts?
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