[jira] [Commented] (HBASE-3693) isMajorCompaction() check triggers lots of listStatus DFS RPC calls from HBase

["Jean-Daniel Cryans (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010250#comment-13010250 ] 

Jean-Daniel Cryans commented on HBASE-3693:
-------------------------------------------

Wow good on your for finding this! +1

> isMajorCompaction() check triggers lots of listStatus DFS RPC calls from HBase
> ------------------------------------------------------------------------------
>
>                 Key: HBASE-3693
>                 URL: https://issues.apache.org/jira/browse/HBASE-3693
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Kannan Muthukkaruppan
>            Assignee: Liyin Tang
>
> We noticed that are lots of listStatus calls on the ColumnFamily directories within each regions, coming from this codepath:
> {code}
> compactionSelection()
>  --> isMajorCompaction 
>     --> getLowestTimestamp()
>        -->  FileStatus[] stats = fs.listStatus(p);
> {code}
> So on every compactionSelection() we're taking this hit. While not immediately an issue, just from log inspection, this accounts for quite a large number of RPCs to namenode at the moment and seems like an unnecessary load to be sending to the namenode.
> Seems like it would be easy to cache the timestamp for each opened/created StoreFile, in memory, in the region server, and avoid going to DFS each time for this information.

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