MAPREDUCE-2889. Added documentation for writing new YARN applications. Contributed by Hitesh Shah.
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1177920 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Arun Murthy
parent
dc8464f943
commit
7aa8a3c9f8
@ -330,6 +330,9 @@ Release 0.23.0 - Unreleased
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MAPREDUCE-3098. Fixed RM and MR AM to report YarnApplicationState and
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MAPREDUCE-3098. Fixed RM and MR AM to report YarnApplicationState and
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application's FinalStatus separately. (Hitesh Shah via vinodkv)
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application's FinalStatus separately. (Hitesh Shah via vinodkv)
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MAPREDUCE-2889. Added documentation for writing new YARN applications.
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(Hitesh Shah via acmurthy)
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OPTIMIZATIONS
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OPTIMIZATIONS
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MAPREDUCE-2026. Make JobTracker.getJobCounters() and
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MAPREDUCE-2026. Make JobTracker.getJobCounters() and
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@ -0,0 +1,31 @@
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<?xml version="1.0" encoding="UTF-8"?>
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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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<project>
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<parent>
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<artifactId>hadoop-yarn</artifactId>
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<groupId>org.apache.hadoop</groupId>
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<version>${yarn.version}</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<groupId>org.apache.hadoop</groupId>
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<artifactId>hadoop-yarn-site</artifactId>
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<name>hadoop-yarn-site</name>
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<properties>
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<install.file>${project.artifact.file}</install.file>
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<yarn.basedir>${project.parent.parent.basedir}</yarn.basedir>
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</properties>
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</project>
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@ -0,0 +1,781 @@
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~~ Licensed under the Apache License, Version 2.0 (the "License");
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~~ you may not use this file except in compliance with the License.
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~~ You may obtain a copy of the License at
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~~
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~~ http://www.apache.org/licenses/LICENSE-2.0
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~~
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~~ Unless required by applicable law or agreed to in writing, software
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~~ distributed under the License is distributed on an "AS IS" BASIS,
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~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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~~ See the License for the specific language governing permissions and
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~~ limitations under the License. See accompanying LICENSE file.
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---
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Hadoop Map Reduce Next Generation-${project.version} - Writing YARN
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Applications
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---
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---
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${maven.build.timestamp}
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Hadoop MapReduce Next Generation - Writing YARN Applications
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\[ {{{./index.html}Go Back}} \]
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%{toc|section=1|fromDepth=1}
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* Purpose
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This document describes, at a high-level, the way to implement new
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Applications for YARN.
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* Concepts and Flow
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The general concept is that an 'Application Submission Client' submits an
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'Application' to the YARN Resource Manager. The client communicates with the
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ResourceManager using the 'ClientRMProtocol' to first acquire a new
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'ApplicationId' if needed via ClientRMProtocol#getNewApplication and then
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submit the 'Application' to be run via ClientRMProtocol#submitApplication. As
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part of the ClientRMProtocol#submitApplication call, the client needs to
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provide sufficient information to the ResourceManager to 'launch' the
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application's first container i.e. the ApplicationMaster.
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You need to provide information such as the details about the local
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files/jars that need to be available for your application to run, the actual
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command that needs to be executed (with the necessary command line arguments),
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any Unix environment settings (optional), etc. Effectively, you need to
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describe the Unix process(es) that needs to be launched for your
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ApplicationMaster.
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The YARN ResourceManager will then launch the ApplicationMaster (as specified)
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on an allocated container. The ApplicationMaster is then expected to
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communicate with the ResourceManager using the 'AMRMProtocol'. Firstly, the
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ApplicationMaster needs to register itself with the ResourceManager. To
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complete the task assigned to it, the ApplicationMaster can then request for
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and receive containers via AMRMProtocol#allocate. After a container is
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allocated to it, the ApplicationMaster communicates with the NodeManager using
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ContainerManager#startContainer to launch the container for its task. As part
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of launching this container, the ApplicationMaster has to specify the
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ContainerLaunchContext which, similar to the ApplicationSubmissionContext,
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has the launch information such as command line specification, environment,
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etc. Once the task is completed, the ApplicationMaster has to signal the
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ResourceManager of its completion via the AMRMProtocol#finishApplicationMaster.
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Meanwhile, the client can monitor the application's status by querying the
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ResourceManager or by directly querying the ApplicationMaster if it supports
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such a service. If needed, it can also kill the application via
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ClientRMProtocol#forceKillApplication.
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* Interfaces
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The interfaces you'd most like be concerned with are:
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* ClientRMProtocol - Client\<--\>ResourceManager\
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The protocol for a client that wishes to communicate with the
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ResourceManager to launch a new application (i.e. the ApplicationMaster),
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check on the status of the application or kill the application. For example,
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a job-client (a job launching program from the gateway) would use this
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protocol.
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* AMRMProtocol - ApplicationMaster\<--\>ResourceManager\
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The protocol used by the ApplicationMaster to register/unregister itself
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to/from the ResourceManager as well as to request for resources from the
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Scheduler to complete its tasks.
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* ContainerManager - ApplicationMaster\<--\>NodeManager\
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The protocol used by the ApplicationMaster to talk to the NodeManager to
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start/stop containers and get status updates on the containers if needed.
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* Writing a Simple Yarn Application
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** Writing a simple Client
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* The first step that a client needs to do is to connect to the
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ResourceManager or to be more specific, the ApplicationsManager (AsM)
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interface of the ResourceManager.
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+---+
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ClientRMProtocol applicationsManager;
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YarnConfiguration yarnConf = new YarnConfiguration(conf);
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InetSocketAddress rmAddress =
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NetUtils.createSocketAddr(yarnConf.get(
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YarnConfiguration.RM_ADDRESS,
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YarnConfiguration.DEFAULT_RM_ADDRESS));
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LOG.info("Connecting to ResourceManager at " + rmAddress);
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configuration appsManagerServerConf = new Configuration(conf);
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appsManagerServerConf.setClass(
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YarnConfiguration.YARN_SECURITY_INFO,
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ClientRMSecurityInfo.class, SecurityInfo.class);
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applicationsManager = ((ClientRMProtocol) rpc.getProxy(
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ClientRMProtocol.class, rmAddress, appsManagerServerConf));
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+---+
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* Once a handle is obtained to the ASM, the client needs to request the
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ResourceManager for a new ApplicationId.
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+---+
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GetNewApplicationRequest request =
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Records.newRecord(GetNewApplicationRequest.class);
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GetNewApplicationResponse response =
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applicationsManager.getNewApplication(request);
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LOG.info("Got new ApplicationId=" + response.getApplicationId());
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+---+
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* The response from the ASM for a new application also contains information
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about the cluster such as the minimum/maximum resource capabilities of the
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cluster. This is required so that to ensure that you can correctly set the
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specifications of the container in which the ApplicationMaster would be
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launched. Please refer to GetNewApplicationResponse for more details.
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* The main crux of a client is to setup the ApplicationSubmissionContext
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which defines all the information needed by the ResourceManager to launch
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the ApplicationMaster. A client needs to set the following into the context:
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* Application Info: id, name
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* Queue, Priority info: Queue to which the application will be submitted,
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the priority to be assigned for the application.
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* User: The user submitting the application
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* ContainerLaunchContext: The information defining the container in which
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the ApplicationMaster will be launched and run. The
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ContainerLaunchContext, as mentioned previously, defines all the required
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information needed to run the ApplicationMaster such as the local
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resources (binaries, jars, files etc.), security tokens, environment
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settings (CLASSPATH etc.) and the command to be executed.
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[]
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+---+
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// Create a new ApplicationSubmissionContext
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ApplicationSubmissionContext appContext =
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Records.newRecord(ApplicationSubmissionContext.class);
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// set the ApplicationId
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appContext.setApplicationId(appId);
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// set the application name
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appContext.setApplicationName(appName);
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// Create a new container launch context for the AM's container
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ContainerLaunchContext amContainer =
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Records.newRecord(ContainerLaunchContext.class);
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// Define the local resources required
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Map<String, LocalResource> localResources =
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new HashMap<String, LocalResource>();
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// Lets assume the jar we need for our ApplicationMaster is available in
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// HDFS at a certain known path to us and we want to make it available to
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// the ApplicationMaster in the launched container
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Path jarPath; // <- known path to jar file
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FileStatus jarStatus = fs.getFileStatus(jarPath);
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LocalResource amJarRsrc = Records.newRecord(LocalResource.class);
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// Set the type of resource - file or archive
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// archives are untarred at the destination by the framework
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amJarRsrc.setType(LocalResourceType.FILE);
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// Set visibility of the resource
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// Setting to most private option i.e. this file will only
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// be visible to this instance of the running application
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amJarRsrc.setVisibility(LocalResourceVisibility.APPLICATION);
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// Set the location of resource to be copied over into the
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// working directory
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amJarRsrc.setResource(ConverterUtils.getYarnUrlFromPath(jarPath));
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// Set timestamp and length of file so that the framework
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// can do basic sanity checks for the local resource
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// after it has been copied over to ensure it is the same
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// resource the client intended to use with the application
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amJarRsrc.setTimestamp(jarStatus.getModificationTime());
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amJarRsrc.setSize(jarStatus.getLen());
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// The framework will create a symlink called AppMaster.jar in the
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// working directory that will be linked back to the actual file.
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// The ApplicationMaster, if needs to reference the jar file, would
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// need to use the symlink filename.
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localResources.put("AppMaster.jar", amJarRsrc);
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// Set the local resources into the launch context
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amContainer.setLocalResources(localResources);
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// Set up the environment needed for the launch context
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Map<String, String> env = new HashMap<String, String>();
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// For example, we could setup the classpath needed.
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// Assuming our classes or jars are available as local resources in the
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// working directory from which the command will be run, we need to append
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// "." to the path.
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// By default, all the hadoop specific classpaths will already be available
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// in $CLASSPATH, so we should be careful not to overwrite it.
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String classPathEnv = "$CLASSPATH:./*:";
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env.put("CLASSPATH", classPathEnv);
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amContainer.setEnvironment(env);
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// Construct the command to be executed on the launched container
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String command =
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"${JAVA_HOME}" + /bin/java" +
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" MyAppMaster" +
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" arg1 arg2 arg3" +
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" 1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stdout" +
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" 2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stderr";
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List<String> commands = new ArrayList<String>();
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commands.add(command);
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// add additional commands if needed
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// Set the command array into the container spec
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amContainer.setCommands(commands);
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// Define the resource requirements for the container
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// For now, YARN only supports memory so we set the memory
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// requirements.
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// If the process takes more than its allocated memory, it will
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// be killed by the framework.
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// Memory being requested for should be less than max capability
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// of the cluster and all asks should be a multiple of the min capability.
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Resource capability = Records.newRecord(Resource.class);
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capability.setMemory(amMemory);
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amContainer.setResource(capability);
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// Set the container launch content into the ApplicationSubmissionContext
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appContext.setAMContainerSpec(amContainer);
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+---+
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* After the setup process is complete, the client is finally ready to submit
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the application to the ASM.
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+---+
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// Create the request to send to the ApplicationsManager
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SubmitApplicationRequest appRequest =
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Records.newRecord(SubmitApplicationRequest.class);
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appRequest.setApplicationSubmissionContext(appContext);
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// Submit the application to the ApplicationsManager
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// Ignore the response as either a valid response object is returned on
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// success or an exception thrown to denote the failure
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applicationsManager.submitApplication(appRequest);
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+---+
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* At this point, the ResourceManager will have accepted the application and
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in the background, will go through the process of allocating a container
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with the required specifications and then eventually setting up and
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launching the ApplicationMaster on the allocated container.
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* There are multiple ways a client can track progress of the actual task.
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* It can communicate with the ResourceManager and request for a report of
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the application via ClientRMProtocol#getApplicationReport.
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+-----+
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GetApplicationReportRequest reportRequest =
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Records.newRecord(GetApplicationReportRequest.class);
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reportRequest.setApplicationId(appId);
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GetApplicationReportResponse reportResponse =
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applicationsManager.getApplicationReport(reportRequest);
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ApplicationReport report = reportResponse.getApplicationReport();
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+-----+
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The ApplicationReport received from the ResourceManager consists of the following:
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* General application information: ApplicationId, queue to which the
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application was submitted, user who submitted the application and the
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start time for the application.
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* ApplicationMaster details: the host on which the ApplicationMaster is
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running, the rpc port (if any) on which it is listening for requests
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from clients and a token that the client needs to communicate with
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the ApplicationMaster.
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* Application tracking information: If the application supports some
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form of progress tracking, it can set a tracking url which is
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available via ApplicationReport#getTrackingUrl that a client can look
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at to monitor progress.
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* ApplicationStatus: The state of the application as seen by the
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ResourceManager is available via
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ApplicationReport#getYarnApplicationState. If the
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YarnApplicationState is set to FINISHED, the client should refer to
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ApplicationReport#getFinalApplicationStatus to check for the actual
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success/failure of the application task itself. In case of failures,
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ApplicationReport#getDiagnostics may be useful to shed some more
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light on the the failure.
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* If the ApplicationMaster supports it, a client can directly query the
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ApplicationMaster itself for progress updates via the host:rpcport
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information obtained from the ApplicationReport. It can also use the
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tracking url obtained from the report if available.
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* In certain situations, if the application is taking too long or due to
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other factors, the client may wish to kill the application. The
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ClientRMProtocol supports the forceKillApplication call that allows a
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client to send a kill signal to the ApplicationMaster via the
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ResourceManager. An ApplicationMaster if so designed may also support an
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abort call via its rpc layer that a client may be able to leverage.
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+---+
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KillApplicationRequest killRequest =
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Records.newRecord(KillApplicationRequest.class);
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killRequest.setApplicationId(appId);
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applicationsManager.forceKillApplication(killRequest);
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+---+
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** Writing an ApplicationMaster
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* The ApplicationMaster is the actual owner of the job. It will be launched
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by the ResourceManager and via the client will be provided all the necessary
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information and resources about the job that it has been tasked with to
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oversee and complete.
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* As the ApplicationMaster is launched within a container that may (likely
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will) be sharing a physical host with other containers, given the
|
||||||
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multi-tenancy nature, amongst other issues, it cannot make any assumptions
|
||||||
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of things like pre-configured ports that it can listen on.
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|
|
||||||
|
* All interactions with the ResourceManager require an ApplicationAttemptId
|
||||||
|
(there can be multiple attempts per application in case of failures). When
|
||||||
|
the ApplicationMaster starts up, the ApplicationAttemptId associated with
|
||||||
|
this particular instance will be set in the environment. There are helper
|
||||||
|
apis to convert the value obtained from the environment into an
|
||||||
|
ApplicationAttemptId object.
|
||||||
|
|
||||||
|
+---+
|
||||||
|
Map<String, String> envs = System.getenv();
|
||||||
|
ApplicationAttemptId appAttemptID =
|
||||||
|
Records.newRecord(ApplicationAttemptId.class);
|
||||||
|
if (!envs.containsKey(ApplicationConstants.APPLICATION_ATTEMPT_ID_ENV)) {
|
||||||
|
// app attempt id should always be set in the env by the framework
|
||||||
|
throw new IllegalArgumentException(
|
||||||
|
"ApplicationAttemptId not set in the environment");
|
||||||
|
}
|
||||||
|
appAttemptID =
|
||||||
|
ConverterUtils.toApplicationAttemptId(
|
||||||
|
envs.get(ApplicationConstants.APPLICATION_ATTEMPT_ID_ENV));
|
||||||
|
+---+
|
||||||
|
|
||||||
|
* After an ApplicationMaster has initialized itself completely, it needs to
|
||||||
|
register with the ResourceManager via
|
||||||
|
AMRMProtocol#registerApplicationMaster. The ApplicationMaster always
|
||||||
|
communicate via the Scheduler interface of the ResourceManager.
|
||||||
|
|
||||||
|
+---+
|
||||||
|
// Connect to the Scheduler of the ResourceManager.
|
||||||
|
YarnConfiguration yarnConf = new YarnConfiguration(conf);
|
||||||
|
InetSocketAddress rmAddress =
|
||||||
|
NetUtils.createSocketAddr(yarnConf.get(
|
||||||
|
YarnConfiguration.RM_SCHEDULER_ADDRESS,
|
||||||
|
YarnConfiguration.DEFAULT_RM_SCHEDULER_ADDRESS));
|
||||||
|
LOG.info("Connecting to ResourceManager at " + rmAddress);
|
||||||
|
AMRMProtocol resourceManager =
|
||||||
|
(AMRMProtocol) rpc.getProxy(AMRMProtocol.class, rmAddress, conf);
|
||||||
|
|
||||||
|
// Register the AM with the RM
|
||||||
|
// Set the required info into the registration request:
|
||||||
|
// ApplicationAttemptId,
|
||||||
|
// host on which the app master is running
|
||||||
|
// rpc port on which the app master accepts requests from the client
|
||||||
|
// tracking url for the client to track app master progress
|
||||||
|
RegisterApplicationMasterRequest appMasterRequest =
|
||||||
|
Records.newRecord(RegisterApplicationMasterRequest.class);
|
||||||
|
appMasterRequest.setApplicationAttemptId(appAttemptID);
|
||||||
|
appMasterRequest.setHost(appMasterHostname);
|
||||||
|
appMasterRequest.setRpcPort(appMasterRpcPort);
|
||||||
|
appMasterRequest.setTrackingUrl(appMasterTrackingUrl);
|
||||||
|
|
||||||
|
// The registration response is useful as it provides information about the
|
||||||
|
// cluster.
|
||||||
|
// Similar to the GetNewApplicationResponse in the client, it provides
|
||||||
|
// information about the min/mx resource capabilities of the cluster that
|
||||||
|
// would be needed by the ApplicationMaster when requesting for containers.
|
||||||
|
RegisterApplicationMasterResponse response =
|
||||||
|
resourceManager.registerApplicationMaster(appMasterRequest);
|
||||||
|
+---+
|
||||||
|
|
||||||
|
* The ApplicationMaster has to emit heartbeats to the ResourceManager to keep
|
||||||
|
it informed that the ApplicationMaster is alive and still running. The
|
||||||
|
timeout expiry interval at the ResourceManager is defined by a config
|
||||||
|
setting accessible via YarnConfiguration.RM_AM_EXPIRY_INTERVAL_MS with the
|
||||||
|
default being defined by YarnConfiguration.DEFAULT_RM_AM_EXPIRY_INTERVAL_MS.
|
||||||
|
The AMRMProtocol#allocate calls to the ResourceManager count as heartbeats
|
||||||
|
as it also supports sending progress update information. Therefore, an
|
||||||
|
allocate call with no containers requested and progress information updated
|
||||||
|
if any is a valid way for making heartbeat calls to the ResourceManager.
|
||||||
|
|
||||||
|
* Based on the task requirements, the ApplicationMaster can ask for a set of
|
||||||
|
containers to run its tasks on. The ApplicationMaster has to use the
|
||||||
|
ResourceRequest class to define the following container specifications:
|
||||||
|
|
||||||
|
* Hostname: If containers are required to be hosted on a particular rack or
|
||||||
|
a specific host. '*' is a special value that implies any host will do.
|
||||||
|
|
||||||
|
* Resource capability: Currently, YARN only supports memory based resource
|
||||||
|
requirements so the request should define how much memory is needed. The
|
||||||
|
value is defined in MB and has to less than the max capability of the
|
||||||
|
cluster and an exact multiple of the min capability.
|
||||||
|
|
||||||
|
* Priority: When asking for sets of containers, an ApplicationMaster may
|
||||||
|
define different priorities to each set. For example, the Map-Reduce
|
||||||
|
ApplicationMaster may assign a higher priority to containers needed
|
||||||
|
for the Map tasks and a lower priority for the Reduce tasks' containers.
|
||||||
|
|
||||||
|
[]
|
||||||
|
|
||||||
|
+----+
|
||||||
|
// Resource Request
|
||||||
|
ResourceRequest rsrcRequest = Records.newRecord(ResourceRequest.class);
|
||||||
|
|
||||||
|
// setup requirements for hosts
|
||||||
|
// whether a particular rack/host is needed
|
||||||
|
// useful for applications that are sensitive
|
||||||
|
// to data locality
|
||||||
|
rsrcRequest.setHostName("*");
|
||||||
|
|
||||||
|
// set the priority for the request
|
||||||
|
Priority pri = Records.newRecord(Priority.class);
|
||||||
|
pri.setPriority(requestPriority);
|
||||||
|
rsrcRequest.setPriority(pri);
|
||||||
|
|
||||||
|
// Set up resource type requirements
|
||||||
|
// For now, only memory is supported so we set memory requirements
|
||||||
|
Resource capability = Records.newRecord(Resource.class);
|
||||||
|
capability.setMemory(containerMemory);
|
||||||
|
rsrcRequest.setCapability(capability);
|
||||||
|
|
||||||
|
// set no. of containers needed
|
||||||
|
// matching the specifications
|
||||||
|
rsrcRequest.setNumContainers(numContainers);
|
||||||
|
+---+
|
||||||
|
|
||||||
|
* After defining the container requirements, the ApplicationMaster has to
|
||||||
|
construct an AllocateRequest to send to the ResourceManager.
|
||||||
|
The AllocateRequest consists of:
|
||||||
|
|
||||||
|
* Requested containers: The container specifications and the no. of
|
||||||
|
containers being requested for by the ApplicationMaster from the
|
||||||
|
ResourceManager.
|
||||||
|
|
||||||
|
* Released containers: There may be situations when the ApplicationMaster
|
||||||
|
may have requested for more containers that it needs or due to failure
|
||||||
|
issues, decide to use other containers allocated to it. In all such
|
||||||
|
situations, it is beneficial to the cluster if the ApplicationMaster
|
||||||
|
releases these containers back to the ResourceManager so that they can be
|
||||||
|
re-allocated to other applications.
|
||||||
|
|
||||||
|
* ResponseId: The response id that will be sent back in the response from
|
||||||
|
the allocate call.
|
||||||
|
|
||||||
|
* Progress update information: The ApplicationMaster can send its progress
|
||||||
|
update (range between to 0 to 1) to the ResourceManager.
|
||||||
|
|
||||||
|
[]
|
||||||
|
|
||||||
|
+---+
|
||||||
|
List<ResourceRequest> requestedContainers;
|
||||||
|
List<ContainerId> releasedContainers
|
||||||
|
AllocateRequest req = Records.newRecord(AllocateRequest.class);
|
||||||
|
|
||||||
|
// The response id set in the request will be sent back in
|
||||||
|
// the response so that the ApplicationMaster can
|
||||||
|
// match it to its original ask and act appropriately.
|
||||||
|
req.setResponseId(rmRequestID);
|
||||||
|
|
||||||
|
// Set ApplicationAttemptId
|
||||||
|
req.setApplicationAttemptId(appAttemptID);
|
||||||
|
|
||||||
|
// Add the list of containers being asked for
|
||||||
|
req.addAllAsks(requestedContainers);
|
||||||
|
|
||||||
|
// If the ApplicationMaster has no need for certain
|
||||||
|
// containers due to over-allocation or for any other
|
||||||
|
// reason, it can release them back to the ResourceManager
|
||||||
|
req.addAllReleases(releasedContainers);
|
||||||
|
|
||||||
|
// Assuming the ApplicationMaster can track its progress
|
||||||
|
req.setProgress(currentProgress);
|
||||||
|
|
||||||
|
AllocateResponse allocateResponse = resourceManager.allocate(req);
|
||||||
|
+---+
|
||||||
|
|
||||||
|
* The AllocateResponse sent back from the ResourceManager provides the
|
||||||
|
following information via the AMResponse object:
|
||||||
|
|
||||||
|
* Reboot flag: For scenarios when the ApplicationMaster may get out of sync
|
||||||
|
with the ResourceManager.
|
||||||
|
|
||||||
|
* Allocated containers: The containers that have been allocated to the
|
||||||
|
ApplicationMaster.
|
||||||
|
|
||||||
|
* Headroom: Headroom for resources in the cluster. Based on this information
|
||||||
|
and knowing its needs, an ApplicationMaster can make intelligent decisions
|
||||||
|
such as re-prioritizing sub-tasks to take advantage of currently allocated
|
||||||
|
containers, bailing out faster if resources are not becoming available
|
||||||
|
etc.
|
||||||
|
|
||||||
|
* Completed containers: Once an ApplicationMaster triggers a launch an
|
||||||
|
allocated container, it will receive an update from the ResourceManager
|
||||||
|
when the container completes. The ApplicationMaster can look into the
|
||||||
|
status of the completed container and take appropriate actions such as
|
||||||
|
re-trying a particular sub-task in case of a failure.
|
||||||
|
|
||||||
|
[]
|
||||||
|
|
||||||
|
One thing to note is that containers will not be immediately allocated to
|
||||||
|
the ApplicationMaster. This does not imply that the ApplicationMaster should
|
||||||
|
keep on asking the pending count of required containers. Once an allocate
|
||||||
|
request has been sent, the ApplicationMaster will eventually be allocated
|
||||||
|
the containers based on cluster capacity, priorities and the scheduling
|
||||||
|
policy in place. The ApplicationMaster should only request for containers
|
||||||
|
again if and only if its original estimate changed and it needs additional
|
||||||
|
containers.
|
||||||
|
|
||||||
|
+---+
|
||||||
|
// Get AMResponse from AllocateResponse
|
||||||
|
AMResponse amResp = allocateResponse.getAMResponse();
|
||||||
|
|
||||||
|
// Retrieve list of allocated containers from the response
|
||||||
|
// and on each allocated container, lets assume we are launching
|
||||||
|
// the same job.
|
||||||
|
List<Container> allocatedContainers = amResp.getAllocatedContainers();
|
||||||
|
for (Container allocatedContainer : allocatedContainers) {
|
||||||
|
LOG.info("Launching shell command on a new container."
|
||||||
|
+ ", containerId=" + allocatedContainer.getId()
|
||||||
|
+ ", containerNode=" + allocatedContainer.getNodeId().getHost()
|
||||||
|
+ ":" + allocatedContainer.getNodeId().getPort()
|
||||||
|
+ ", containerNodeURI=" + allocatedContainer.getNodeHttpAddress()
|
||||||
|
+ ", containerState" + allocatedContainer.getState()
|
||||||
|
+ ", containerResourceMemory"
|
||||||
|
+ allocatedContainer.getResource().getMemory());
|
||||||
|
|
||||||
|
|
||||||
|
// Launch and start the container on a separate thread to keep the main
|
||||||
|
// thread unblocked as all containers may not be allocated at one go.
|
||||||
|
LaunchContainerRunnable runnableLaunchContainer =
|
||||||
|
new LaunchContainerRunnable(allocatedContainer);
|
||||||
|
Thread launchThread = new Thread(runnableLaunchContainer);
|
||||||
|
launchThreads.add(launchThread);
|
||||||
|
launchThread.start();
|
||||||
|
}
|
||||||
|
|
||||||
|
// Check what the current available resources in the cluster are
|
||||||
|
Resource availableResources = amResp.getAvailableResources();
|
||||||
|
// Based on this information, an ApplicationMaster can make appropriate
|
||||||
|
// decisions
|
||||||
|
|
||||||
|
// Check the completed containers
|
||||||
|
// Let's assume we are keeping a count of total completed containers,
|
||||||
|
// containers that failed and ones that completed successfully.
|
||||||
|
List<ContainerStatus> completedContainers =
|
||||||
|
amResp.getCompletedContainersStatuses();
|
||||||
|
for (ContainerStatus containerStatus : completedContainers) {
|
||||||
|
LOG.info("Got container status for containerID= "
|
||||||
|
+ containerStatus.getContainerId()
|
||||||
|
+ ", state=" + containerStatus.getState()
|
||||||
|
+ ", exitStatus=" + containerStatus.getExitStatus()
|
||||||
|
+ ", diagnostics=" + containerStatus.getDiagnostics());
|
||||||
|
|
||||||
|
int exitStatus = containerStatus.getExitStatus();
|
||||||
|
if (0 != exitStatus) {
|
||||||
|
// container failed
|
||||||
|
// -100 is a special case where the container
|
||||||
|
// was aborted/pre-empted for some reason
|
||||||
|
if (-100 != exitStatus) {
|
||||||
|
// application job on container returned a non-zero exit code
|
||||||
|
// counts as completed
|
||||||
|
numCompletedContainers.incrementAndGet();
|
||||||
|
numFailedContainers.incrementAndGet();
|
||||||
|
}
|
||||||
|
else {
|
||||||
|
// something else bad happened
|
||||||
|
// app job did not complete for some reason
|
||||||
|
// we should re-try as the container was lost for some reason
|
||||||
|
// decrementing the requested count so that we ask for an
|
||||||
|
// additional one in the next allocate call.
|
||||||
|
numRequestedContainers.decrementAndGet();
|
||||||
|
// we do not need to release the container as that has already
|
||||||
|
// been done by the ResourceManager/NodeManager.
|
||||||
|
}
|
||||||
|
}
|
||||||
|
else {
|
||||||
|
// nothing to do
|
||||||
|
// container completed successfully
|
||||||
|
numCompletedContainers.incrementAndGet();
|
||||||
|
numSuccessfulContainers.incrementAndGet();
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
+---+
|
||||||
|
|
||||||
|
|
||||||
|
* After a container has been allocated to the ApplicationMaster, it needs to
|
||||||
|
follow a similar process that the Client followed in setting up the
|
||||||
|
ContainerLaunchContext for the eventual task that is going to be running on
|
||||||
|
the allocated Container. Once the ContainerLaunchContext is defined, the
|
||||||
|
ApplicationMaster can then communicate with the ContainerManager to start
|
||||||
|
its allocated container.
|
||||||
|
|
||||||
|
+---+
|
||||||
|
|
||||||
|
//Assuming an allocated Container obtained from AMResponse
|
||||||
|
Container container;
|
||||||
|
// Connect to ContainerManager on the allocated container
|
||||||
|
String cmIpPortStr = container.getNodeId().getHost() + ":"
|
||||||
|
+ container.getNodeId().getPort();
|
||||||
|
InetSocketAddress cmAddress = NetUtils.createSocketAddr(cmIpPortStr);
|
||||||
|
ContainerManager cm =
|
||||||
|
(ContainerManager)rpc.getProxy(ContainerManager.class, cmAddress, conf);
|
||||||
|
|
||||||
|
// Now we setup a ContainerLaunchContext
|
||||||
|
ContainerLaunchContext ctx =
|
||||||
|
Records.newRecord(ContainerLaunchContext.class);
|
||||||
|
|
||||||
|
ctx.setContainerId(container.getId());
|
||||||
|
ctx.setResource(container.getResource());
|
||||||
|
|
||||||
|
try {
|
||||||
|
ctx.setUser(UserGroupInformation.getCurrentUser().getShortUserName());
|
||||||
|
} catch (IOException e) {
|
||||||
|
LOG.info(
|
||||||
|
"Getting current user failed when trying to launch the container",
|
||||||
|
+ e.getMessage());
|
||||||
|
}
|
||||||
|
|
||||||
|
// Set the environment
|
||||||
|
Map<String, String> unixEnv;
|
||||||
|
// Setup the required env.
|
||||||
|
// Please note that the launched container does not inherit
|
||||||
|
// the environment of the ApplicationMaster so all the
|
||||||
|
// necessary environment settings will need to be re-setup
|
||||||
|
// for this allocated container.
|
||||||
|
ctx.setEnvironment(unixEnv);
|
||||||
|
|
||||||
|
// Set the local resources
|
||||||
|
Map<String, LocalResource> localResources =
|
||||||
|
new HashMap<String, LocalResource>();
|
||||||
|
// Again, the local resources from the ApplicationMaster is not copied over
|
||||||
|
// by default to the allocated container. Thus, it is the responsibility
|
||||||
|
// of the ApplicationMaster to setup all the necessary local resources
|
||||||
|
// needed by the job that will be executed on the allocated container.
|
||||||
|
|
||||||
|
// Assume that we are executing a shell script on the allocated container
|
||||||
|
// and the shell script's location in the filesystem is known to us.
|
||||||
|
Path shellScriptPath;
|
||||||
|
LocalResource shellRsrc = Records.newRecord(LocalResource.class);
|
||||||
|
shellRsrc.setType(LocalResourceType.FILE);
|
||||||
|
shellRsrc.setVisibility(LocalResourceVisibility.APPLICATION);
|
||||||
|
shellRsrc.setResource(
|
||||||
|
ConverterUtils.getYarnUrlFromURI(new URI(shellScriptPath)));
|
||||||
|
shellRsrc.setTimestamp(shellScriptPathTimestamp);
|
||||||
|
shellRsrc.setSize(shellScriptPathLen);
|
||||||
|
localResources.put("MyExecShell.sh", shellRsrc);
|
||||||
|
|
||||||
|
ctx.setLocalResources(localResources);
|
||||||
|
|
||||||
|
// Set the necessary command to execute on the allocated container
|
||||||
|
String command = "/bin/sh ./MyExecShell.sh"
|
||||||
|
+ " 1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stdout"
|
||||||
|
+ " 2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stderr";
|
||||||
|
|
||||||
|
List<String> commands = new ArrayList<String>();
|
||||||
|
commands.add(command);
|
||||||
|
ctx.setCommands(commands);
|
||||||
|
|
||||||
|
// Send the start request to the ContainerManager
|
||||||
|
StartContainerRequest startReq = Records.newRecord(StartContainerRequest.class);
|
||||||
|
startReq.setContainerLaunchContext(ctx);
|
||||||
|
cm.startContainer(startReq);
|
||||||
|
+---+
|
||||||
|
|
||||||
|
* The ApplicationMaster, as mentioned previously, will get updates of
|
||||||
|
completed containers as part of the response from the AMRMProtocol#allocate
|
||||||
|
calls. It can also monitor its launched containers pro-actively by querying
|
||||||
|
the ContainerManager for the status.
|
||||||
|
|
||||||
|
+---+
|
||||||
|
|
||||||
|
GetContainerStatusRequest statusReq =
|
||||||
|
Records.newRecord(GetContainerStatusRequest.class);
|
||||||
|
statusReq.setContainerId(container.getId());
|
||||||
|
GetContainerStatusResponse statusResp = cm.getContainerStatus(statusReq);
|
||||||
|
LOG.info("Container Status"
|
||||||
|
+ ", id=" + container.getId()
|
||||||
|
+ ", status=" + statusResp.getStatus());
|
||||||
|
+---+
|
||||||
|
|
||||||
|
~~** Defining the context in which your code runs
|
||||||
|
|
||||||
|
~~*** Container Resource Requests
|
||||||
|
|
||||||
|
~~*** Local Resources
|
||||||
|
|
||||||
|
~~*** Environment
|
||||||
|
|
||||||
|
~~**** Managing the CLASSPATH
|
||||||
|
|
||||||
|
~~** Security
|
||||||
|
|
||||||
|
* FAQ
|
||||||
|
|
||||||
|
** How can I distribute my application's jars to all of the nodes in the YARN
|
||||||
|
cluster that need it?
|
||||||
|
|
||||||
|
You can use the LocalResource to add resources to your application request.
|
||||||
|
This will cause YARN to distribute the resource to the ApplicationMaster node.
|
||||||
|
If the resource is a tgz, zip, or jar - you can have YARN unzip it. Then, all
|
||||||
|
you need to do is add the unzipped folder to your classpath.
|
||||||
|
For example, when creating your application request:
|
||||||
|
|
||||||
|
+---+
|
||||||
|
File packageFile = new File(packagePath);
|
||||||
|
Url packageUrl = ConverterUtils.getYarnUrlFromPath(
|
||||||
|
FileContext.getFileContext.makeQualified(new Path(packagePath)));
|
||||||
|
|
||||||
|
packageResource.setResource(packageUrl);
|
||||||
|
packageResource.setSize(packageFile.length());
|
||||||
|
packageResource.setTimestamp(packageFile.lastModified());
|
||||||
|
packageResource.setType(LocalResourceType.ARCHIVE);
|
||||||
|
packageResource.setVisibility(LocalResourceVisibility.APPLICATION);
|
||||||
|
|
||||||
|
resource.setMemory(memory)
|
||||||
|
containerCtx.setResource(resource)
|
||||||
|
containerCtx.setCommands(ImmutableList.of(
|
||||||
|
"java -cp './package/*' some.class.to.Run "
|
||||||
|
+ "1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stdout "
|
||||||
|
+ "2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stderr"))
|
||||||
|
containerCtx.setLocalResources(
|
||||||
|
Collections.singletonMap("package", packageResource))
|
||||||
|
appCtx.setApplicationId(appId)
|
||||||
|
appCtx.setUser(user.getShortUserName)
|
||||||
|
appCtx.setAMContainerSpec(containerCtx)
|
||||||
|
request.setApplicationSubmissionContext(appCtx)
|
||||||
|
applicationsManager.submitApplication(request)
|
||||||
|
+---+
|
||||||
|
|
||||||
|
As you can see, the setLocalResources command takes a map of names to
|
||||||
|
resources. The name becomes a sym link in your application's cwd, so you can
|
||||||
|
just refer to the artifacts inside by using ./package/*.
|
||||||
|
|
||||||
|
Note: Java's classpath (cp) argument is VERY sensitive.
|
||||||
|
Make sure you get the syntax EXACTLY correct.
|
||||||
|
|
||||||
|
Once your package is distributed to your ApplicationMaster, you'll need to
|
||||||
|
follow the same process whenever your ApplicationMaster starts a new container
|
||||||
|
(assuming you want the resources to be sent to your container). The code for
|
||||||
|
this is the same. You just need to make sure that you give your
|
||||||
|
ApplicationMaster the package path (either HDFS, or local), so that it can
|
||||||
|
send the resource URL along with the container ctx.
|
||||||
|
|
||||||
|
** How do I get the ApplicationMaster's ApplicationAttemptId?
|
||||||
|
|
||||||
|
|
||||||
|
The ApplicationAttemptId will be passed to the ApplicationMaster via the
|
||||||
|
environment and the value from the environment can be converted into an
|
||||||
|
ApplicationAttemptId object via the ConverterUtils helper function.
|
||||||
|
|
||||||
|
** My container is being killed by the Node Manager
|
||||||
|
|
||||||
|
This is likely due to high memory usage exceeding your requested container
|
||||||
|
memory size. There are a number of reasons that can cause this. First, look
|
||||||
|
at the process tree that the node manager dumps when it kills your container.
|
||||||
|
The two things you're interested in are physical memory and virtual memory.
|
||||||
|
If you have exceeded physical memory limits your app is using too much physical
|
||||||
|
memory. If you're running a Java app, you can use -hprof to look at what is
|
||||||
|
taking up space in the heap. If you have exceeded virtual memory, things are
|
||||||
|
slightly more complicated.
|
||||||
|
|
||||||
|
* Useful Links
|
||||||
|
|
||||||
|
* {{{https://issues.apache.org/jira/secure/attachment/12486023/MapReduce_NextGen_Architecture.pdf}Map Reduce Next Generation Architecture}}
|
||||||
|
|
||||||
|
* {{{http://developer.yahoo.com/blogs/hadoop/posts/2011/03/mapreduce-nextgen-scheduler/}Map Reduce Next Generation Scheduler}}
|
||||||
|
|
||||||
@ -0,0 +1,47 @@
|
|||||||
|
~~ Licensed under the Apache License, Version 2.0 (the "License");
|
||||||
|
~~ you may not use this file except in compliance with the License.
|
||||||
|
~~ You may obtain a copy of the License at
|
||||||
|
~~
|
||||||
|
~~ http://www.apache.org/licenses/LICENSE-2.0
|
||||||
|
~~
|
||||||
|
~~ Unless required by applicable law or agreed to in writing, software
|
||||||
|
~~ distributed under the License is distributed on an "AS IS" BASIS,
|
||||||
|
~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
||||||
|
~~ See the License for the specific language governing permissions and
|
||||||
|
~~ limitations under the License. See accompanying LICENSE file.
|
||||||
|
|
||||||
|
---
|
||||||
|
Hadoop MapReduce Next Generation ${project.version}
|
||||||
|
---
|
||||||
|
---
|
||||||
|
${maven.build.timestamp}
|
||||||
|
|
||||||
|
Hadoop MapReduce Next Generation
|
||||||
|
|
||||||
|
* Architecture
|
||||||
|
|
||||||
|
The new architecture introduced in hadoop-0.23, divides the two major
|
||||||
|
functions of the JobTracker: resource management and job life-cycle management
|
||||||
|
into separate components.
|
||||||
|
|
||||||
|
The new ResourceManager manages the global assignment of compute resources to
|
||||||
|
applications and the per-application ApplicationMaster manages the
|
||||||
|
application’s scheduling and coordination.
|
||||||
|
|
||||||
|
An application is either a single job in the sense of classic MapReduce jobs
|
||||||
|
or a DAG of such jobs.
|
||||||
|
|
||||||
|
The ResourceManager and per-machine NodeManager daemon, which manages the
|
||||||
|
user processes on that machine, form the computation fabric. The
|
||||||
|
per-application ApplicationMaster is, in effect, a framework specific library
|
||||||
|
and is tasked with negotiating resources from the ResourceManager and working
|
||||||
|
with the NodeManager(s) to execute and monitor the tasks.
|
||||||
|
|
||||||
|
* User Documentation
|
||||||
|
|
||||||
|
* {{{./SingleCluster.html}Setting up a Single Node Cluster}}
|
||||||
|
|
||||||
|
* {{{./apidocs/index.html}JavaDocs}}
|
||||||
|
|
||||||
|
* {{{./WritingYarnApplications.html}Writing Yarn Applications}}
|
||||||
|
|
||||||
@ -425,5 +425,6 @@
|
|||||||
<module>hadoop-yarn-common</module>
|
<module>hadoop-yarn-common</module>
|
||||||
<module>hadoop-yarn-server</module>
|
<module>hadoop-yarn-server</module>
|
||||||
<module>hadoop-yarn-applications</module>
|
<module>hadoop-yarn-applications</module>
|
||||||
|
<module>hadoop-yarn-site</module>
|
||||||
</modules>
|
</modules>
|
||||||
</project>
|
</project>
|
||||||
|
|||||||
@ -1,39 +0,0 @@
|
|||||||
~~ Licensed under the Apache License, Version 2.0 (the "License");
|
|
||||||
~~ you may not use this file except in compliance with the License.
|
|
||||||
~~ You may obtain a copy of the License at
|
|
||||||
~~
|
|
||||||
~~ http://www.apache.org/licenses/LICENSE-2.0
|
|
||||||
~~
|
|
||||||
~~ Unless required by applicable law or agreed to in writing, software
|
|
||||||
~~ distributed under the License is distributed on an "AS IS" BASIS,
|
|
||||||
~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
||||||
~~ See the License for the specific language governing permissions and
|
|
||||||
~~ limitations under the License. See accompanying LICENSE file.
|
|
||||||
|
|
||||||
---
|
|
||||||
Hadoop MapReduce Next Generation ${project.version}
|
|
||||||
---
|
|
||||||
---
|
|
||||||
${maven.build.timestamp}
|
|
||||||
|
|
||||||
Hadoop MapReduce Next Generation
|
|
||||||
|
|
||||||
* Architecture
|
|
||||||
|
|
||||||
The new architecture introduced in 0.23, divides the two major functions
|
|
||||||
of the JobTracker, resource management and job scheduling/monitoring, into separate
|
|
||||||
components.
|
|
||||||
The new ResourceManager manages the global assignment of compute resources to applications
|
|
||||||
and the per-application ApplicationMaster manages the application’s scheduling and coordination.
|
|
||||||
An application is either a single job in the classic MapReduce jobs or a DAG of such jobs.
|
|
||||||
The ResourceManager and per-machine NodeManager server, which manages the user processes on that
|
|
||||||
machine, form the computation fabric. The per-application ApplicationMaster is, in effect, a
|
|
||||||
framework specific library and is tasked with negotiating resources from the ResourceManager
|
|
||||||
and working with the NodeManager(s) to execute and monitor the tasks.
|
|
||||||
|
|
||||||
* User Documentation
|
|
||||||
|
|
||||||
* {{{./SingleCluster.html}SingleCluster}}
|
|
||||||
|
|
||||||
* {{{./apidocs/index.html}JavaDocs}}
|
|
||||||
|
|
||||||
Loading…
Reference in New Issue
Block a user