[jira] [Commented] (HBASE-27752) Update the list of prefetched files upon region movement

["Wellington Chevreuil (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-27752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17712313#comment-17712313 ] 

Wellington Chevreuil commented on HBASE-27752:
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So the issue here is regarding graceful restarts. If we want to avoid the need for prefetching blocks again for same files we have in the cache before, we would need to set hbase.rs.evictblocksonclose to false, in order to avoid blocks from being evicted. The problem with this is that now we don't evict blocks on region move.

One solution we could explore here is to avoid eviction on close during graceful stops only (CloseRegionHandler) if cache persistence is enabled, so that hbase.rs.evictblocksonclose can be set to true (evicting blocks on region moves). There would still be potential blocks left over if regions are assigned on other RSes during the restart, then not re-opened on the restarted RS. This could be mitigated by setting hbase.master.scp.retain.assignment.force and hbase.master.scp.retain.assignment.

> Update the list of prefetched files upon region movement
> --------------------------------------------------------
>
>                 Key: HBASE-27752
>                 URL: https://issues.apache.org/jira/browse/HBASE-27752
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>            Reporter: Shanmukha Haripriya Kota
>            Assignee: Shanmukha Haripriya Kota
>            Priority: Major
>
> Currently, we maintain a list of Hfiles on disk for which prefetch is complete and avoid prefetching those files after a restart. But we don't handle cases where blocks are evicted from the cache. This ticket is for updating the list of prefetched files when the region is moved but the blocks from that region are not evicted.



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