[jira] [Resolved] (HDFS-9520) PeerCache evicts too frequently causing connection restablishments

["Chris Nauroth (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-9520?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chris Nauroth resolved HDFS-9520.
---------------------------------
    Resolution: Won't Fix

I'm resolving this as Won't Fix as per prior discussion.  (Please feel free to reopen if there are further thoughts on configuration tuning.)

> 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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