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https://issues.apache.org/jira/browse/TEZ-3754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16083027#comment-16083027
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Siddharth Seth commented on TEZ-3754:
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[~rajesh.balamohan] - what is the corner case in which this is hit? Each time
there's a host with pending input and a fetcher slot available?
I was somehow under the impression that we handled the WAIT case better. Wonder
if it regressed at some point.
Is the plan to track previous fetched inputs for size, so that the connection
is not re-established?, or maybe remember just the last fetched size for a host.
Does this block 0.9?
> With large ordered fetches, stalling shuffle could lead to slowdown of job
> --------------------------------------------------------------------------
>
> Key: TEZ-3754
> URL: https://issues.apache.org/jira/browse/TEZ-3754
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Attachments: TEZ-3754.1.patch
>
>
> When large ordered fetches are getting downloaded, depending on the memory
> availability in merger, it is possible to stall the shuffle ({{Type::WAIT}}).
> This happens after establishing the connection,validation at server side etc.
> However, depending on memory availability allocator could return
> {{Type::WAIT}} to retry fetching later.
> In corner cases, retries happen very frequently and this creates pressure on
> the server side. Server side populates the headers and starts sending the map
> output. This effort is wasted in the client side as data is not downloaded.
> When multiple nodes have similar issue, following connections timesout (180
> seconds), which turns out to be
> very expensive.
> {noformat}
> 2017-06-06 04:27:49,574 [INFO] [fetcher {Map_1} #44]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#44 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,575 [INFO] [fetcher {Map_1} #31]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,575 [INFO] [fetcher {Map_1} #31]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#31 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,576 [INFO] [fetcher {Map_1} #43]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,576 [INFO] [fetcher {Map_1} #43]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#43 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,578 [INFO] [fetcher {Map_1} #32]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,578 [INFO] [fetcher {Map_1} #32]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#32 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,579 [INFO] [fetcher {Map_1} #42]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,579 [INFO] [fetcher {Map_1} #42]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#42 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,580 [INFO] [fetcher {Map_1} #33]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,580 [INFO] [fetcher {Map_1} #33]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#33 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,581 [INFO] [fetcher {Map_1} #41]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,581 [INFO] [fetcher {Map_1} #41]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#41 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,583 [INFO] [fetcher {Map_1} #34]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,583 [INFO] [fetcher {Map_1} #34]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#34 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,584 [INFO] [fetcher {Map_1} #40]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,584 [INFO] [fetcher {Map_1} #40]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#40 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,586 [INFO] [fetcher {Map_1} #35]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,586 [INFO] [fetcher {Map_1} #35]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#35 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,587 [INFO] [fetcher {Map_1} #39]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,587 [INFO] [fetcher {Map_1} #39]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#39 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,588 [INFO] [fetcher {Map_1} #36]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,588 [INFO] [fetcher {Map_1} #36]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#36 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,589 [INFO] [fetcher {Map_1} #38]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000841_1_10008,attempt_1496458948260_0050_1_00_000843_0_10007
> sent hash and receievd reply 0 ms
> 2017-06-06 04:27:49,589 [INFO] [fetcher {Map_1} #38]
> |orderedgrouped.FetcherOrderedGrouped|: fetcher#38 - MergerManager returned
> Status.WAIT ...
> 2017-06-06 04:27:49,590 [INFO] [fetcher {Map_1} #37]
> |shuffle.HttpConnection|: for
> url=http://ctr-e133-1493418528701-76897-01-000005:13562/mapOutput?job=job_1496458948260_0050&reduce=1931&map=attempt_1496458948260_0050_1_00_000843_0_10007,attempt_1496458948260_0050_1_00_000841_1_10008
> sent hash and receievd reply 0 ms
> {noformat}
> In such cases, it would be good to wait until {{usedMemory}} gets released
> during "next" iteration as opposed to retrying immediately.
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