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

["Rajesh Balamohan (JIRA)" <ji...@apache.org>]

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

Rajesh Balamohan updated HDFS-9520:
-----------------------------------
    Attachment: HDFS-9520.png

> 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. Ideally it should not be evicting the connections since "dfs.client.socketcache.capacity" is set to 20 (no. of DN). 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()) ?
> \cc [~gopalv], [~sseth]



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