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Date: Tue, 25 Mar 2008 07:49:25 -0700 (PDT)
From: "Rick Cox (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Created: (HADOOP-3089) streaming should accept stderr from
 task before first key arrives
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streaming should accept stderr from task before first key arrives
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                 Key: HADOOP-3089
                 URL: https://issues.apache.org/jira/browse/HADOOP-3089
             Project: Hadoop Core
          Issue Type: Bug
          Components: contrib/streaming
    Affects Versions: 0.16.1, 0.16.0, 0.15.3, 0.15.2, 0.15.1, 0.15.0, 0.14.4, 0.14.3, 0.14.2, 0.14.1, 0.14.0
            Reporter: Rick Cox
            Assignee: Rick Cox
             Fix For: 0.17.0


Stderr output from a streaming task is not collected until the {{MRErrorThread}} is started by {{PipeMapRed.startOutputThreads()}}, which is done on the first call to {{map()}} or {{reduce()}}.

This makes it difficult to debug failures in starting up the task process. It can also lead to deadlock when a task receives no input keys but produces significant stderr output: the process will block on writing to stderr, while streaming will block waiting for the process to exit.

We should start the {{MRErrorThread}} when the process is forked, and then add the {{reporter}} later to enable stderr output serve as a keep-alive.

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