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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9520) PeerCache evicts too frequently causing connection restablishments
Date Wed, 20 Jan 2016 20:16:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15109320#comment-15109320
] 

Chris Nauroth commented on HDFS-9520:
-------------------------------------

[~rajesh.balamohan], as per the prior comments from me and Colin, we cannot make the suggested
code change.  Shall we resolve this as Won't Fix?  Alternatively, do you want to keep it open
as a request to increase the default cache capacity like Colin described?

> PeerCache evicts too frequently causing connection restablishments
> ------------------------------------------------------------------
>
>                 Key: HDFS-9520
>                 URL: https://issues.apache.org/jira/browse/HDFS-9520
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Rajesh Balamohan
>         Attachments: HDFS-9520.png
>
>
> Env: 20 node setup
> dfs.client.socketcache.capacity = 16
> Issue:
> ======
> Monitored PeerCache and it was evicting lots of connections during close. Set "dfs.client.socketcache.capacity=20"
and tested again. Evictions still happened. Screenshot of profiler is attached in the JIRA.
> Workaround:
> ===========
> Temp fix was to set "dfs.client.socketcache.capacity=1000" to prevent eviction. 
> Added more debug logs revealed that multimap.size() was 40 instead of 20. LinkedListMultimap
returns the total values instead of key size causing lots of evictions.
> {code}
>    if (capacity == multimap.size()) {
>       evictOldest();
>     }
> {code}
> Should this be (capacity == multimap.keySet().size())  or is it expected that the "dfs.client.socketcache.capacity"
be set to very high value?
> \cc [~gopalv], [~sseth]



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