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Yang, Tong
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Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com> Co-authored-by: Yang, Tong <yangtong2@huawei.com> Co-committed-by: Yang, Tong <yangtong2@huawei.com>
42 lines
3.8 KiB
HTML
42 lines
3.8 KiB
HTML
<a name="mrs_01_0848"></a><a name="mrs_01_0848"></a>
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<h1 class="topictitle1">Speculative Execution</h1>
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<div id="body1590130630213"><div class="section" id="mrs_01_0848__sa326bbb79104456189573e739aab283f"><h4 class="sectiontitle">Scenario</h4><p id="mrs_01_0848__ac2cb066bdab849859ff751464e5baf01">If a cluster has hundreds or thousands of nodes, the hardware or software fault of a node may prolong the execution time of the entire task (as most tasks are already completed, the system is still waiting for the task running on the faulty node). Speculative execution allows a task to be executed on multiple machines. You can disable speculative execution for small clusters.</p>
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</div>
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<div class="section" id="mrs_01_0848__s0ff3eba98c364304a9ce2f51b35eb4f6"><h4 class="sectiontitle">Procedure</h4><p id="mrs_01_0848__ab90aa7b1a33447c087187ddae1d072ea">Navigation path for setting parameters:</p>
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<p id="mrs_01_0848__p139709455225">On the <strong id="mrs_01_0848__b113766154012">All Configurations</strong> page of the Yarn service, enter a parameter name in the search box. For details, see <a href="mrs_01_2125.html">Modifying Cluster Service Configuration Parameters</a>.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" id="mrs_01_0848__t6b2d520e110c4c6c8cdbefa4198c02f9" frame="border" border="1" rules="all"><thead align="left"><tr id="mrs_01_0848__rb438328302d54f7a92b610e383a6ff64"><th align="left" class="cellrowborder" valign="top" width="32.45675432456754%" id="mcps1.3.2.4.1.4.1.1"><p id="mrs_01_0848__a18488cf95a31430699ac8f92da1b5cb9"><strong id="mrs_01_0848__b822163481513">Parameter</strong></p>
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<th align="left" class="cellrowborder" valign="top" width="46.865313468653135%" id="mcps1.3.2.4.1.4.1.2"><p id="mrs_01_0848__a0c3f72011ae84834a37111b0c62bc9d1"><strong id="mrs_01_0848__b1875413412156">Description</strong></p>
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<th align="left" class="cellrowborder" valign="top" width="20.677932206779325%" id="mcps1.3.2.4.1.4.1.3"><p id="mrs_01_0848__af127a8ad844648faa7ab35fe8ada319f"><strong id="mrs_01_0848__b177012035101517">Default Value</strong></p>
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</th>
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</tr>
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</thead>
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<tbody><tr id="mrs_01_0848__r96a4714fbb0742479d5e4a414d9c1d33"><td class="cellrowborder" valign="top" width="32.45675432456754%" headers="mcps1.3.2.4.1.4.1.1 "><p id="mrs_01_0848__aa99a5283e80b4f35a642f6863cec75ef">mapreduce.map.speculative</p>
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<td class="cellrowborder" valign="top" width="46.865313468653135%" headers="mcps1.3.2.4.1.4.1.2 "><p id="mrs_01_0848__a9815ab7a4e584f66ac3aeb1924c1bc15">Sets whether to execute multiple instances of some map tasks concurrently. <strong id="mrs_01_0848__b01189861616">true</strong> indicates that speculative execution is enabled.</p>
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<td class="cellrowborder" valign="top" width="20.677932206779325%" headers="mcps1.3.2.4.1.4.1.3 "><p id="mrs_01_0848__a648110aa56d04e30a3ad8820f784b11b">false</p>
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</td>
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</tr>
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<tr id="mrs_01_0848__rb6bf72f8850b44f5b4a5edc36b7dc8b1"><td class="cellrowborder" valign="top" width="32.45675432456754%" headers="mcps1.3.2.4.1.4.1.1 "><p id="mrs_01_0848__a848562c7a9484e2e8527e84125f8365f">mapreduce.reduce.speculative</p>
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</td>
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<td class="cellrowborder" valign="top" width="46.865313468653135%" headers="mcps1.3.2.4.1.4.1.2 "><p id="mrs_01_0848__a071bd002a8a342d0858885865f942bff">Sets whether to execute multiple instances of some reduce tasks concurrently. <strong id="mrs_01_0848__b132376255168">true</strong> indicates that speculative execution is enabled.</p>
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<td class="cellrowborder" valign="top" width="20.677932206779325%" headers="mcps1.3.2.4.1.4.1.3 "><p id="mrs_01_0848__abf676bc1cd1f4699a9fb735216d6c1e6">false</p>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="mrs_01_0843.html">MapReduce Performance Tuning</a></div>
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</div>
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</div>
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