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https://issues.apache.org/jira/browse/MAPREDUCE-5042?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13596332#comment-13596332
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Jason Lowe commented on MAPREDUCE-5042:
---------------------------------------
I thought about the upload-to-staging-for-future-attempts solution but it
seemed passing the secret in the job credentials was a bit cleaner and avoided
the extra HDFS operations.
As for splitting the job token into shuffle and task, I didn't want to change
the current task authentication behavior. Allowing an old task attempt to
authenticate with a new app attempt seemed like it would be a problem waiting
to happen. But we need the shuffle secret to persist across app attempts,
hence the push to split them as part of this change.
> Reducer unable to fetch for a map task that was recovered
> ---------------------------------------------------------
>
> Key: MAPREDUCE-5042
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5042
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mr-am, security
> Affects Versions: 0.23.7, 2.0.5-beta
> Reporter: Jason Lowe
> Assignee: Jason Lowe
> Priority: Blocker
> Attachments: MAPREDUCE-5042.patch, MAPREDUCE-5042.patch
>
>
> If an application attempt fails and is relaunched the AM will try to recover
> previously completed tasks. If a reducer needs to fetch the output of a map
> task attempt that was recovered then it will fail with a 401 error like this:
> {noformat}
> java.io.IOException: Server returned HTTP response code: 401 for URL:
> http://xx:xx/mapOutput?job=job_1361569180491_21845&reduce=0&map=attempt_1361569180491_21845_m_000016_0
> at
> sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1615)
> at
> org.apache.hadoop.mapreduce.task.reduce.Fetcher.copyFromHost(Fetcher.java:231)
> at org.apache.hadoop.mapreduce.task.reduce.Fetcher.run(Fetcher.java:156)
> {noformat}
> Looking at the corresponding NM's logs, we see the shuffle failed due to
> "Verification of the hashReply failed".
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