YARN-2632. Document NM Restart feature. Contributed by Junping Du and Vinod Kumar Vavilapalli
(cherry picked from commit 1e215e8ba2)
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Jason Lowe
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a5764cb783
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@ -124,6 +124,7 @@
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<item name="Writing YARN Applications" href="hadoop-yarn/hadoop-yarn-site/WritingYarnApplications.html"/>
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<item name="YARN Commands" href="hadoop-yarn/hadoop-yarn-site/YarnCommands.html"/>
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<item name="Scheduler Load Simulator" href="hadoop-sls/SchedulerLoadSimulator.html"/>
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<item name="NodeManager Restart" href="hadoop-yarn/hadoop-yarn-site/NodeManagerRestart.html"/>
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</menu>
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<menu name="YARN REST APIs" inherit="top">
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@ -168,6 +168,9 @@ Release 2.6.0 - UNRELEASED
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YARN-2647. Added a queue CLI for getting queue information. (Sunil Govind via
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vinodkv)
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YARN-2632. Document NM Restart feature. (Junping Du and Vinod Kumar
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Vavilapalli via jlowe)
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IMPROVEMENTS
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YARN-2242. Improve exception information on AM launch crashes. (Li Lu
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@ -0,0 +1,86 @@
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~~ Licensed under the Apache License, Version 2.0 (the "License");
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~~ you may not use this file except in compliance with the License.
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~~ You may obtain a copy of the License at
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~~
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~~ http://www.apache.org/licenses/LICENSE-2.0
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~~
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~~ Unless required by applicable law or agreed to in writing, software
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~~ distributed under the License is distributed on an "AS IS" BASIS,
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~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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~~ See the License for the specific language governing permissions and
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~~ limitations under the License. See accompanying LICENSE file.
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---
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NodeManager Restart
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---
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---
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${maven.build.timestamp}
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NodeManager Restart
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* Introduction
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This document gives an overview of NodeManager (NM) restart, a feature that
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enables the NodeManager to be restarted without losing
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the active containers running on the node. At a high level, the NM stores any
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necessary state to a local state-store as it processes container-management
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requests. When the NM restarts, it recovers by first loading state for
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various subsystems and then letting those subsystems perform recovery using
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the loaded state.
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* Enabling NM Restart
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[[1]] To enable NM Restart functionality, set the following property in <<conf/yarn-site.xml>> to true:
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*--------------------------------------+--------------------------------------+
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|| Property || Value |
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*--------------------------------------+--------------------------------------+
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| <<<yarn.nodemanager.recovery.enabled>>> | |
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| | <<<true>>>, (default value is set to false) |
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*--------------------------------------+--------------------------------------+
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[[2]] Configure a path to the local file-system directory where the
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NodeManager can save its run state
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*--------------------------------------+--------------------------------------+
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|| Property || Description |
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*--------------------------------------+--------------------------------------+
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| <<<yarn.nodemanager.recovery.dir>>> | |
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| | The local filesystem directory in which the node manager will store state |
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| | when recovery is enabled. |
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| | The default value is set to |
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| | <<<${hadoop.tmp.dir}/yarn-nm-recovery>>>. |
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*--------------------------------------+--------------------------------------+
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[[3]] Configure a valid RPC address for the NodeManager
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*--------------------------------------+--------------------------------------+
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|| Property || Description |
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*--------------------------------------+--------------------------------------+
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| <<<yarn.nodemanager.address>>> | |
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| | Ephemeral ports (port 0, which is default) cannot be used for the |
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| | NodeManager's RPC server specified via yarn.nodemanager.address as it can |
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| | make NM use different ports before and after a restart. This will break any |
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| | previously running clients that were communicating with the NM before |
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| | restart. Explicitly setting yarn.nodemanager.address to an address with |
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| | specific port number (for e.g 0.0.0.0:45454) is a precondition for enabling |
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| | NM restart. |
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*--------------------------------------+--------------------------------------+
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[[4]] Auxiliary services
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NodeManagers in a YARN cluster can be configured to run auxiliary services.
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For a completely functional NM restart, YARN relies on any auxiliary service
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configured to also support recovery. This usually includes (1) avoiding usage
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of ephemeral ports so that previously running clients (in this case, usually
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containers) are not disrupted after restart and (2) having the auxiliary
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service itself support recoverability by reloading any previous state when
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NodeManager restarts and reinitializes the auxiliary service.
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A simple example for the above is the auxiliary service 'ShuffleHandler' for
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MapReduce (MR). ShuffleHandler respects the above two requirements already,
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so users/admins don't have do anything for it to support NM restart: (1) The
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configuration property <<mapreduce.shuffle.port>> controls which port the
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ShuffleHandler on a NodeManager host binds to, and it defaults to a
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non-ephemeral port. (2) The ShuffleHandler service also already supports
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recovery of previous state after NM restarts.
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