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From "Rakesh R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11164) Mover should avoid unnecessary retries if the block is pinned
Date Fri, 25 Nov 2016 18:42:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11164?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15696466#comment-15696466
] 

Rakesh R commented on HDFS-11164:
---------------------------------

Thanks [~umamaheswararao] for the comments. 

bq. One thought is, Failed blocks due to pinned can be stored separately and when retry happens
and if blocks exist in failedDueToPinned list, then skip to add them into PendingMoves? Just
a thought, we need to check the feasibility.
Yes, we can maintain a datastructure to hold the {{blockId vs pinnedBlkLocations}}, there
could be multiple favored/pinned nodes for a "blockId". Let me try implementing this excluded
logic. In worst case, I could see a case of millions of pinned block entries and this data
structure will consume more memory throughout the lifetime of Mover tool. Do we need to introduce
any configuration parameter to limit the size of this data structure.
{code}
int LIMIT = // configured value, default to 10K.
Map<Long, Set<DatanodeInfo>> excludedPinnedBlocks = new HashMap<>(LIMIT);
{code}

> Mover should avoid unnecessary retries if the block is pinned
> -------------------------------------------------------------
>
>                 Key: HDFS-11164
>                 URL: https://issues.apache.org/jira/browse/HDFS-11164
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: balancer & mover
>            Reporter: Rakesh R
>            Assignee: Rakesh R
>         Attachments: HDFS-11164-00.patch, HDFS-11164-01.patch
>
>
> When mover is trying to move a pinned block to another datanode, it will internally hits
the following IOException and mark the block movement as {{failure}}. Since the Mover has
{{dfs.mover.retry.max.attempts}} configs, it will continue moving this block until it reaches
{{retryMaxAttempts}}. If the block movement failure(s) are only due to block pinning, then
retry is unnecessary. The idea of this jira is to avoid retry attempts of pinned blocks as
they won't be able to move to a different node. 
> {code}
> 2016-11-22 10:56:10,537 WARN org.apache.hadoop.hdfs.server.balancer.Dispatcher: Failed
to move blk_1073741825_1001 with size=52 from 127.0.0.1:19501:DISK to 127.0.0.1:19758:ARCHIVE
through 127.0.0.1:19501
> java.io.IOException: Got error, status=ERROR, status message opReplaceBlock BP-1772076264-10.252.146.200-1479792322960:blk_1073741825_1001
received exception java.io.IOException: Got error, status=ERROR, status message Not able to
copy block 1073741825 to /127.0.0.1:19826 because it's pinned , copy block BP-1772076264-10.252.146.200-1479792322960:blk_1073741825_1001
from /127.0.0.1:19501, reportedBlock move is failed
> 	at org.apache.hadoop.hdfs.protocol.datatransfer.DataTransferProtoUtil.checkBlockOpStatus(DataTransferProtoUtil.java:118)
> 	at org.apache.hadoop.hdfs.server.balancer.Dispatcher$PendingMove.receiveResponse(Dispatcher.java:417)
> 	at org.apache.hadoop.hdfs.server.balancer.Dispatcher$PendingMove.dispatch(Dispatcher.java:358)
> 	at org.apache.hadoop.hdfs.server.balancer.Dispatcher$PendingMove.access$5(Dispatcher.java:322)
> 	at org.apache.hadoop.hdfs.server.balancer.Dispatcher$1.run(Dispatcher.java:1075)
> 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> 	at java.lang.Thread.run(Thread.java:745)
> {code}



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