YARN-3174. Consolidate the NodeManager and NodeManagerRestart documentation into one. Contributed by Masatake Iwasaki.
(cherry picked from commit f02dd146f5)
This commit is contained in:
Tsuyoshi Ozawa
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f3f7872fbf
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f95e3c3091
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@ -123,7 +123,7 @@
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<item name="Web Application Proxy" href="hadoop-yarn/hadoop-yarn-site/WebApplicationProxy.html"/>
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<item name="Timeline Server" href="hadoop-yarn/hadoop-yarn-site/TimelineServer.html"/>
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<item name="Writing YARN Applications" href="hadoop-yarn/hadoop-yarn-site/WritingYarnApplications.html"/>
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<item name="NodeManager Restart" href="hadoop-yarn/hadoop-yarn-site/NodeManagerRestart.html"/>
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<item name="NodeManager" href="hadoop-yarn/hadoop-yarn-site/NodeManager.html"/>
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<item name="DockerContainerExecutor" href="hadoop-yarn/hadoop-yarn-site/DockerContainerExecutor.html"/>
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<item name="Using CGroups" href="hadoop-yarn/hadoop-yarn-site/NodeManagerCgroups.html"/>
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<item name="Secure Containers" href="hadoop-yarn/hadoop-yarn-site/SecureContainer.html"/>
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@ -583,6 +583,9 @@ Release 2.8.0 - UNRELEASED
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YARN-3453. Ensure preemption logic in FairScheduler uses DominantResourceCalculator
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in DRF queues to prevent unnecessary thrashing. (asuresh)
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YARN-3174. Consolidate the NodeManager and NodeManagerRestart documentation
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into one. (Masatake Iwasaki via ozawa)
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Release 2.7.2 - UNRELEASED
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INCOMPATIBLE CHANGES
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@ -12,19 +12,23 @@
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limitations under the License. See accompanying LICENSE file.
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-->
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NodeManager Overview
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=====================
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NodeManager
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===========
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* [Overview](#Overview)
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* [Health Checker Service](#Health_checker_service)
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* [Disk Checker](#Disk_Checker)
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* [External Health Script](#External_Health_Script)
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* [NodeManager Restart](#NodeManager_Restart)
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* [Introduction](#Introduction)
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* [Enabling NM Restart](#Enabling_NM_Restart)
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Overview
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--------
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The NodeManager is responsible for launching and managing containers on a node. Containers execute tasks as specified by the AppMaster.
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Health Checker Service
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----------------------
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@ -42,7 +46,6 @@ The NodeManager runs services to determine the health of the node it is executin
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| `yarn.nodemanager.disk-health-checker.max-disk-utilization-per-disk-percentage` | Float between 0-100 | The maximum percentage of disk space that may be utilized before a disk is marked as unhealthy by the disk checker service. This check is run for every disk used by the NodeManager. The default value is 100 i.e. the entire disk can be used. |
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| `yarn.nodemanager.disk-health-checker.min-free-space-per-disk-mb` | Integer | The minimum amount of free space that must be available on the disk for the disk checker service to mark the disk as healthy. This check is run for every disk used by the NodeManager. The default value is 0 i.e. the entire disk can be used. |
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###External Health Script
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Users may specify their own health checker script that will be invoked by the health checker service. Users may specify a timeout as well as options to be passed to the script. If the script exits with a non-zero exit code, times out or results in an exception being thrown, the node is marked as unhealthy. Please note that if the script cannot be executed due to permissions or an incorrect path, etc, then it counts as a failure and the node will be reported as unhealthy. Please note that speifying a health check script is not mandatory. If no script is specified, only the disk checker status will be used to determine the health of the node. The following configuration parameters can be used to set the health script:
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@ -55,3 +58,35 @@ The NodeManager runs services to determine the health of the node it is executin
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| `yarn.nodemanager.health-checker.script.opts` | String | Arguments to be passed to the script when the script is executed. |
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NodeManager Restart
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-------------------
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### Introduction
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This document gives an overview of NodeManager (NM) restart, a feature that enables the NodeManager to be restarted without losing the active containers running on the node. At a high level, the NM stores any necessary state to a local state-store as it processes container-management requests. When the NM restarts, it recovers by first loading state for various subsystems and then letting those subsystems perform recovery using the loaded state.
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### Enabling NM Restart
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Step 1. To enable NM Restart functionality, set the following property in **conf/yarn-site.xml** to *true*.
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| Property | Value |
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|:---- |:---- |
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| `yarn.nodemanager.recovery.enabled` | `true`, (default value is set to false) |
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Step 2. Configure a path to the local file-system directory where the NodeManager can save its run state.
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| Property | Description |
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|:---- |:---- |
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| `yarn.nodemanager.recovery.dir` | The local filesystem directory in which the node manager will store state when recovery is enabled. The default value is set to `$hadoop.tmp.dir/yarn-nm-recovery`. |
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Step 3. Configure a valid RPC address for the NodeManager.
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| Property | Description |
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|:---- |:---- |
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| `yarn.nodemanager.address` | Ephemeral ports (port 0, which is default) cannot be used for the NodeManager's RPC server specified via yarn.nodemanager.address as it can make NM use different ports before and after a restart. This will break any previously running clients that were communicating with the NM before restart. Explicitly setting yarn.nodemanager.address to an address with specific port number (for e.g 0.0.0.0:45454) is a precondition for enabling NM restart. |
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Step 4. Auxiliary services.
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* NodeManagers in a YARN cluster can be configured to run auxiliary services. For a completely functional NM restart, YARN relies on any auxiliary service configured to also support recovery. This usually includes (1) avoiding usage of ephemeral ports so that previously running clients (in this case, usually containers) are not disrupted after restart and (2) having the auxiliary service itself support recoverability by reloading any previous state when NodeManager restarts and reinitializes the auxiliary service.
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* A simple example for the above is the auxiliary service 'ShuffleHandler' for MapReduce (MR). ShuffleHandler respects the above two requirements already, so users/admins don't have do anything for it to support NM restart: (1) The configuration property **mapreduce.shuffle.port** controls which port the ShuffleHandler on a NodeManager host binds to, and it defaults to a non-ephemeral port. (2) The ShuffleHandler service also already supports recovery of previous state after NM restarts.
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@ -1,53 +0,0 @@
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<!---
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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* [Introduction](#Introduction)
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* [Enabling NM Restart](#Enabling_NM_Restart)
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Introduction
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------------
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This document gives an overview of NodeManager (NM) restart, a feature that enables the NodeManager to be restarted without losing the active containers running on the node. At a high level, the NM stores any necessary state to a local state-store as it processes container-management requests. When the NM restarts, it recovers by first loading state for various subsystems and then letting those subsystems perform recovery using the loaded state.
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Enabling NM Restart
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-------------------
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Step 1. To enable NM Restart functionality, set the following property in **conf/yarn-site.xml** to *true*.
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| Property | Value |
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|:---- |:---- |
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| `yarn.nodemanager.recovery.enabled` | `true`, (default value is set to false) |
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Step 2. Configure a path to the local file-system directory where the NodeManager can save its run state.
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| Property | Description |
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|:---- |:---- |
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| `yarn.nodemanager.recovery.dir` | The local filesystem directory in which the node manager will store state when recovery is enabled. The default value is set to `$hadoop.tmp.dir/yarn-nm-recovery`. |
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Step 3. Configure a valid RPC address for the NodeManager.
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| Property | Description |
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|:---- |:---- |
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| `yarn.nodemanager.address` | Ephemeral ports (port 0, which is default) cannot be used for the NodeManager's RPC server specified via yarn.nodemanager.address as it can make NM use different ports before and after a restart. This will break any previously running clients that were communicating with the NM before restart. Explicitly setting yarn.nodemanager.address to an address with specific port number (for e.g 0.0.0.0:45454) is a precondition for enabling NM restart. |
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Step 4. Auxiliary services.
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* NodeManagers in a YARN cluster can be configured to run auxiliary services. For a completely functional NM restart, YARN relies on any auxiliary service configured to also support recovery. This usually includes (1) avoiding usage of ephemeral ports so that previously running clients (in this case, usually containers) are not disrupted after restart and (2) having the auxiliary service itself support recoverability by reloading any previous state when NodeManager restarts and reinitializes the auxiliary service.
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* A simple example for the above is the auxiliary service 'ShuffleHandler' for MapReduce (MR). ShuffleHandler respects the above two requirements already, so users/admins don't have do anything for it to support NM restart: (1) The configuration property **mapreduce.shuffle.port** controls which port the ShuffleHandler on a NodeManager host binds to, and it defaults to a non-ephemeral port. (2) The ShuffleHandler service also already supports recovery of previous state after NM restarts.
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