org.dknight.app.Client.java Source code

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package org.dknight.app;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Vector;

import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.GnuParser;
import org.apache.commons.cli.HelpFormatter;
import org.apache.commons.cli.Options;
import org.apache.commons.cli.ParseException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.security.Credentials;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.yarn.api.ApplicationClientProtocol;
import org.apache.hadoop.yarn.api.ApplicationConstants;
import org.apache.hadoop.yarn.api.ApplicationConstants.Environment;
import org.apache.hadoop.yarn.api.protocolrecords.GetNewApplicationResponse;
import org.apache.hadoop.yarn.api.protocolrecords.KillApplicationRequest;
import org.apache.hadoop.yarn.api.records.ApplicationId;
import org.apache.hadoop.yarn.api.records.ApplicationReport;
import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
import org.apache.hadoop.yarn.api.records.ContainerLaunchContext;
import org.apache.hadoop.yarn.api.records.FinalApplicationStatus;
import org.apache.hadoop.yarn.api.records.LocalResource;
import org.apache.hadoop.yarn.api.records.LocalResourceType;
import org.apache.hadoop.yarn.api.records.LocalResourceVisibility;
import org.apache.hadoop.yarn.api.records.NodeReport;
import org.apache.hadoop.yarn.api.records.NodeState;
import org.apache.hadoop.yarn.api.records.Priority;
import org.apache.hadoop.yarn.api.records.QueueACL;
import org.apache.hadoop.yarn.api.records.QueueInfo;
import org.apache.hadoop.yarn.api.records.QueueUserACLInfo;
import org.apache.hadoop.yarn.api.records.Resource;
import org.apache.hadoop.yarn.api.records.YarnApplicationState;
import org.apache.hadoop.yarn.api.records.YarnClusterMetrics;
import org.apache.hadoop.yarn.client.api.YarnClient;
import org.apache.hadoop.yarn.client.api.YarnClientApplication;
import org.apache.hadoop.yarn.conf.YarnConfiguration;
import org.apache.hadoop.yarn.exceptions.YarnException;
import org.apache.hadoop.yarn.util.ConverterUtils;
import org.apache.hadoop.yarn.util.Records;

/**
 * Client for Distributed Shell application submission to YARN.
 * 
 * <p> The distributed shell client allows an application master to be launched that in turn would run 
 * the provided shell command on a set of containers. </p>
 * 
 * <p>This client is meant to act as an example on how to write yarn-based applications. </p>
 * 
 * <p> To submit an application, a client first needs to connect to the <code>ResourceManager</code> 
 * aka ApplicationsManager or ASM via the {@link ApplicationClientProtocol}. The {@link ApplicationClientProtocol} 
 * provides a way for the client to get access to cluster information and to request for a
 * new {@link ApplicationId}. <p>
 * 
 * <p> For the actual job submission, the client first has to create an {@link ApplicationSubmissionContext}. 
 * The {@link ApplicationSubmissionContext} defines the application details such as {@link ApplicationId} 
 * and application name, the priority assigned to the application and the queue
 * to which this application needs to be assigned. In addition to this, the {@link ApplicationSubmissionContext}
 * also defines the {@link ContainerLaunchContext} which describes the <code>Container</code> with which 
 * the {@link ApplicationMaster} is launched. </p>
 * 
 * <p> The {@link ContainerLaunchContext} in this scenario defines the resources to be allocated for the 
 * {@link ApplicationMaster}'s container, the local resources (jars, configuration files) to be made available 
 * and the environment to be set for the {@link ApplicationMaster} and the commands to be executed to run the 
 * {@link ApplicationMaster}. <p>
 * 
 * <p> Using the {@link ApplicationSubmissionContext}, the client submits the application to the 
 * <code>ResourceManager</code> and then monitors the application by requesting the <code>ResourceManager</code> 
 * for an {@link ApplicationReport} at regular time intervals. In case of the application taking too long, the client 
 * kills the application by submitting a {@link KillApplicationRequest} to the <code>ResourceManager</code>. </p>
 *
 */
@InterfaceAudience.Public
@InterfaceStability.Unstable
public class Client {

    private static final Log LOG = LogFactory.getLog(Client.class);

    // Configuration
    private Configuration conf;
    private YarnClient yarnClient;
    // Application master specific info to register a new Application with RM/ASM
    private String appName = "";
    // App master priority
    private int amPriority = 0;
    // Queue for App master
    private String amQueue = "";
    // Amt. of memory resource to request for to run the App Master
    private int amMemory = 10;

    // Application master jar file
    private String appMasterJar = "";
    // Main class to invoke application master
    private final String appMasterMainClass;

    // Shell command to be executed 
    private String shellCommand = "";
    // Location of shell script 
    private String shellScriptPath = "";
    // Args to be passed to the shell command
    private String shellArgs = "";
    // Env variables to be setup for the shell command 
    private Map<String, String> shellEnv = new HashMap<String, String>();
    // Shell Command Container priority 
    private int shellCmdPriority = 0;

    // Amt of memory to request for container in which shell script will be executed
    private int containerMemory = 10;
    // No. of containers in which the shell script needs to be executed
    private int numContainers = 1;

    // log4j.properties file 
    // if available, add to local resources and set into classpath 
    private String log4jPropFile = "";

    // Start time for client
    private final long clientStartTime = System.currentTimeMillis();
    // Timeout threshold for client. Kill app after time interval expires.
    private long clientTimeout = 600000;

    // Debug flag
    boolean debugFlag = false;

    // Command line options
    private Options opts;

    /**
     * @param args Command line arguments 
     */
    public static void main(String[] args) {
        boolean result = false;
        try {
            Client client = new Client();
            LOG.info("Initializing Client");
            try {
                boolean doRun = client.init(args);
                if (!doRun) {
                    System.exit(0);
                }
            } catch (IllegalArgumentException e) {
                System.err.println(e.getLocalizedMessage());
                client.printUsage();
                System.exit(-1);
            }
            result = client.run();
        } catch (Throwable t) {
            LOG.fatal("Error running CLient", t);
            System.exit(1);
        }
        if (result) {
            LOG.info("Application completed successfully");
            System.exit(0);
        }
        LOG.error("Application failed to complete successfully");
        System.exit(2);
    }

    /**
     */
    public Client(Configuration conf) throws Exception {
        this("org.dknight.app.ApplicationMaster", conf);
    }

    Client(String appMasterMainClass, Configuration conf) {
        this.conf = conf;
        this.appMasterMainClass = appMasterMainClass;
        yarnClient = YarnClient.createYarnClient();
        yarnClient.init(conf);
        opts = new Options();
        opts.addOption("appname", true, "Application Name. Default value - DistributedShell");
        opts.addOption("priority", true, "Application Priority. Default 0");
        opts.addOption("queue", true, "RM Queue in which this application is to be submitted");
        opts.addOption("timeout", true, "Application timeout in milliseconds");
        opts.addOption("master_memory", true,
                "Amount of memory in MB to be requested to run the application master");
        opts.addOption("jar", true, "Jar file containing the application master");
        opts.addOption("shell_command", true, "Shell command to be executed by the Application Master");
        opts.addOption("shell_script", true, "Location of the shell script to be executed");
        opts.addOption("shell_args", true, "Command line args for the shell script");
        opts.addOption("shell_env", true, "Environment for shell script. Specified as env_key=env_val pairs");
        opts.addOption("shell_cmd_priority", true, "Priority for the shell command containers");
        opts.addOption("container_memory", true, "Amount of memory in MB to be requested to run the shell command");
        opts.addOption("num_containers", true, "No. of containers on which the shell command needs to be executed");
        opts.addOption("log_properties", true, "log4j.properties file");
        opts.addOption("debug", false, "Dump out debug information");
        opts.addOption("help", false, "Print usage");

    }

    /**
     */
    public Client() throws Exception {
        this(new YarnConfiguration());
    }

    /**
     * Helper function to print out usage
     */
    private void printUsage() {
        new HelpFormatter().printHelp("Client", opts);
    }

    /**
     * Parse command line options
     * @param args Parsed command line options 
     * @return Whether the init was successful to run the client
     * @throws ParseException
     */
    public boolean init(String[] args) throws ParseException {

        CommandLine cliParser = new GnuParser().parse(opts, args);

        if (args.length == 0) {
            throw new IllegalArgumentException("No args specified for client to initialize");
        }

        if (cliParser.hasOption("help")) {
            printUsage();
            return false;
        }

        if (cliParser.hasOption("debug")) {
            debugFlag = true;

        }

        appName = cliParser.getOptionValue("appname", "DistributedShell");
        amPriority = Integer.parseInt(cliParser.getOptionValue("priority", "0"));
        amQueue = cliParser.getOptionValue("queue", "default");
        amMemory = Integer.parseInt(cliParser.getOptionValue("master_memory", "10"));

        if (amMemory < 0) {
            throw new IllegalArgumentException(
                    "Invalid memory specified for application master, exiting." + " Specified memory=" + amMemory);
        }

        if (!cliParser.hasOption("jar")) {
            throw new IllegalArgumentException("No jar file specified for application master");
        }

        appMasterJar = cliParser.getOptionValue("jar");

        if (!cliParser.hasOption("shell_command")) {
            throw new IllegalArgumentException("No shell command specified to be executed by application master");
        }
        shellCommand = cliParser.getOptionValue("shell_command");

        if (cliParser.hasOption("shell_script")) {
            shellScriptPath = cliParser.getOptionValue("shell_script");
        }
        if (cliParser.hasOption("shell_args")) {
            shellArgs = cliParser.getOptionValue("shell_args");
        }
        if (cliParser.hasOption("shell_env")) {
            String envs[] = cliParser.getOptionValues("shell_env");
            for (String env : envs) {
                env = env.trim();
                int index = env.indexOf('=');
                if (index == -1) {
                    shellEnv.put(env, "");
                    continue;
                }
                String key = env.substring(0, index);
                String val = "";
                if (index < (env.length() - 1)) {
                    val = env.substring(index + 1);
                }
                shellEnv.put(key, val);
            }
        }
        shellCmdPriority = Integer.parseInt(cliParser.getOptionValue("shell_cmd_priority", "0"));

        containerMemory = Integer.parseInt(cliParser.getOptionValue("container_memory", "10"));
        numContainers = Integer.parseInt(cliParser.getOptionValue("num_containers", "1"));

        if (containerMemory < 0 || numContainers < 1) {
            throw new IllegalArgumentException("Invalid no. of containers or container memory specified, exiting."
                    + " Specified containerMemory=" + containerMemory + ", numContainer=" + numContainers);
        }

        clientTimeout = Integer.parseInt(cliParser.getOptionValue("timeout", "600000"));

        log4jPropFile = cliParser.getOptionValue("log_properties", "");

        return true;
    }

    /**
     * Main run function for the client
     * @return true if application completed successfully
     * @throws IOException
     * @throws YarnException
     */
    public boolean run() throws IOException, YarnException {

        LOG.info("Running Client");
        yarnClient.start();

        YarnClusterMetrics clusterMetrics = yarnClient.getYarnClusterMetrics();
        LOG.info("Got Cluster metric info from ASM" + ", numNodeManagers=" + clusterMetrics.getNumNodeManagers());

        List<NodeReport> clusterNodeReports = yarnClient.getNodeReports(NodeState.RUNNING);
        LOG.info("Got Cluster node info from ASM");
        for (NodeReport node : clusterNodeReports) {
            LOG.info("Got node report from ASM for" + ", nodeId=" + node.getNodeId() + ", nodeAddress"
                    + node.getHttpAddress() + ", nodeRackName" + node.getRackName() + ", nodeNumContainers"
                    + node.getNumContainers());
        }

        QueueInfo queueInfo = yarnClient.getQueueInfo(this.amQueue);
        LOG.info("Queue info" + ", queueName=" + queueInfo.getQueueName() + ", queueCurrentCapacity="
                + queueInfo.getCurrentCapacity() + ", queueMaxCapacity=" + queueInfo.getMaximumCapacity()
                + ", queueApplicationCount=" + queueInfo.getApplications().size() + ", queueChildQueueCount="
                + queueInfo.getChildQueues().size());

        List<QueueUserACLInfo> listAclInfo = yarnClient.getQueueAclsInfo();
        for (QueueUserACLInfo aclInfo : listAclInfo) {
            for (QueueACL userAcl : aclInfo.getUserAcls()) {
                LOG.info("User ACL Info for Queue" + ", queueName=" + aclInfo.getQueueName() + ", userAcl="
                        + userAcl.name());
            }
        }

        // Get a new application id
        YarnClientApplication app = yarnClient.createApplication();
        GetNewApplicationResponse appResponse = app.getNewApplicationResponse();
        // TODO get min/max resource capabilities from RM and change memory ask if needed
        // If we do not have min/max, we may not be able to correctly request 
        // the required resources from the RM for the app master
        // Memory ask has to be a multiple of min and less than max. 
        // Dump out information about cluster capability as seen by the resource manager
        int maxMem = appResponse.getMaximumResourceCapability().getMemory();
        LOG.info("Max mem capabililty of resources in this cluster " + maxMem);

        // A resource ask cannot exceed the max. 
        if (amMemory > maxMem) {
            LOG.info("AM memory specified above max threshold of cluster. Using max value." + ", specified="
                    + amMemory + ", max=" + maxMem);
            amMemory = maxMem;
        }

        // set the application name
        ApplicationSubmissionContext appContext = app.getApplicationSubmissionContext();
        ApplicationId appId = appContext.getApplicationId();
        appContext.setApplicationName(appName);

        // Set up the container launch context for the application master
        ContainerLaunchContext amContainer = Records.newRecord(ContainerLaunchContext.class);

        // set local resources for the application master
        // local files or archives as needed
        // In this scenario, the jar file for the application master is part of the local resources         
        Map<String, LocalResource> localResources = new HashMap<String, LocalResource>();

        LOG.info("Copy App Master jar from local filesystem and add to local environment");
        // Copy the application master jar to the filesystem 
        // Create a local resource to point to the destination jar path 
        FileSystem fs = FileSystem.get(conf);
        Path src = new Path(appMasterJar);
        String pathSuffix = appName + "/" + appId.getId() + "/AppMaster.jar";
        Path dst = new Path(fs.getHomeDirectory(), pathSuffix);
        fs.copyFromLocalFile(false, true, src, dst);
        FileStatus destStatus = fs.getFileStatus(dst);
        LocalResource amJarRsrc = Records.newRecord(LocalResource.class);

        // Set the type of resource - file or archive
        // archives are untarred at destination
        // we don't need the jar file to be untarred for now
        amJarRsrc.setType(LocalResourceType.FILE);
        // Set visibility of the resource 
        // Setting to most private option
        amJarRsrc.setVisibility(LocalResourceVisibility.APPLICATION);
        // Set the resource to be copied over
        amJarRsrc.setResource(ConverterUtils.getYarnUrlFromPath(dst));
        // Set timestamp and length of file so that the framework 
        // can do basic sanity checks for the local resource 
        // after it has been copied over to ensure it is the same 
        // resource the client intended to use with the application
        amJarRsrc.setTimestamp(destStatus.getModificationTime());
        amJarRsrc.setSize(destStatus.getLen());
        localResources.put("AppMaster.jar", amJarRsrc);

        String confXMLFSPath = "";
        {
            File clusterConfXML = new File("cluster-conf.xml");
            conf.writeXml(new FileOutputStream(clusterConfXML));
            Path confSrc = new Path(clusterConfXML.getAbsolutePath());
            String confPathSuffix = appName + "/" + appId.getId() + "/cluster-conf.xml";
            Path confDst = new Path(fs.getHomeDirectory(), confPathSuffix);
            fs.copyFromLocalFile(false, true, confSrc, confDst);
            FileStatus confFileStatus = fs.getFileStatus(confDst);
            LocalResource confRsrc = Records.newRecord(LocalResource.class);
            confRsrc.setType(LocalResourceType.FILE);
            confRsrc.setVisibility(LocalResourceVisibility.APPLICATION);
            confRsrc.setResource(ConverterUtils.getYarnUrlFromURI(confDst.toUri()));
            confRsrc.setSize(confFileStatus.getLen());
            confRsrc.setTimestamp(confFileStatus.getModificationTime());
            localResources.put("cluster-conf.xml", confRsrc);
            confXMLFSPath = confDst.toUri().getPath();
        }

        // Set the log4j properties if needed 
        if (!log4jPropFile.isEmpty()) {
            Path log4jSrc = new Path(log4jPropFile);
            Path log4jDst = new Path(fs.getHomeDirectory(), "log4j.props");
            fs.copyFromLocalFile(false, true, log4jSrc, log4jDst);
            FileStatus log4jFileStatus = fs.getFileStatus(log4jDst);
            LocalResource log4jRsrc = Records.newRecord(LocalResource.class);
            log4jRsrc.setType(LocalResourceType.FILE);
            log4jRsrc.setVisibility(LocalResourceVisibility.APPLICATION);
            log4jRsrc.setResource(ConverterUtils.getYarnUrlFromURI(log4jDst.toUri()));
            log4jRsrc.setTimestamp(log4jFileStatus.getModificationTime());
            log4jRsrc.setSize(log4jFileStatus.getLen());
            localResources.put("log4j.properties", log4jRsrc);
        }

        // The shell script has to be made available on the final container(s)
        // where it will be executed. 
        // To do this, we need to first copy into the filesystem that is visible 
        // to the yarn framework. 
        // We do not need to set this as a local resource for the application 
        // master as the application master does not need it.       
        String hdfsShellScriptLocation = "";
        long hdfsShellScriptLen = 0;
        long hdfsShellScriptTimestamp = 0;
        if (!shellScriptPath.isEmpty()) {
            Path shellSrc = new Path(shellScriptPath);
            String shellPathSuffix = appName + "/" + appId.getId() + "/ExecShellScript.sh";
            Path shellDst = new Path(fs.getHomeDirectory(), shellPathSuffix);
            fs.copyFromLocalFile(false, true, shellSrc, shellDst);
            hdfsShellScriptLocation = shellDst.toUri().toString();
            FileStatus shellFileStatus = fs.getFileStatus(shellDst);
            hdfsShellScriptLen = shellFileStatus.getLen();
            hdfsShellScriptTimestamp = shellFileStatus.getModificationTime();
        }

        // Set local resource info into app master container launch context
        amContainer.setLocalResources(localResources);

        // Set the necessary security tokens as needed
        //amContainer.setContainerTokens(containerToken);

        // Set the env variables to be setup in the env where the application master will be run
        LOG.info("Set the environment for the application master");
        Map<String, String> env = new HashMap<String, String>();

        // put location of shell script into env
        // using the env info, the application master will create the correct local resource for the 
        // eventual containers that will be launched to execute the shell scripts
        env.put(DSConstants.DISTRIBUTEDSHELLSCRIPTLOCATION, hdfsShellScriptLocation);
        env.put(DSConstants.DISTRIBUTEDSHELLSCRIPTTIMESTAMP, Long.toString(hdfsShellScriptTimestamp));
        env.put(DSConstants.DISTRIBUTEDSHELLSCRIPTLEN, Long.toString(hdfsShellScriptLen));
        env.put(DSConstants.CLUSTER_CONF_XML_PATH, confXMLFSPath);

        // Add AppMaster.jar location to classpath       
        // At some point we should not be required to add 
        // the hadoop specific classpaths to the env. 
        // It should be provided out of the box. 
        // For now setting all required classpaths including
        // the classpath to "." for the application jar
        StringBuilder classPathEnv = new StringBuilder(Environment.CLASSPATH.$()).append(File.pathSeparatorChar)
                .append("./*");
        for (String c : conf.getStrings(YarnConfiguration.YARN_APPLICATION_CLASSPATH,
                YarnConfiguration.DEFAULT_YARN_APPLICATION_CLASSPATH)) {
            classPathEnv.append(File.pathSeparatorChar);
            classPathEnv.append(c.trim());
        }
        classPathEnv.append(File.pathSeparatorChar).append("./log4j.properties");

        // add the runtime classpath needed for tests to work
        if (conf.getBoolean(YarnConfiguration.IS_MINI_YARN_CLUSTER, false)) {
            classPathEnv.append(':');
            classPathEnv.append(System.getProperty("java.class.path"));
        }

        env.put("CLASSPATH", classPathEnv.toString());

        amContainer.setEnvironment(env);

        // Set the necessary command to execute the application master 
        Vector<CharSequence> vargs = new Vector<CharSequence>(30);

        // Set java executable command 
        LOG.info("Setting up app master command");
        vargs.add(Environment.JAVA_HOME.$() + "/bin/java");
        // Set Xmx based on am memory size
        vargs.add("-Xmx" + amMemory + "m");
        //      if (debugFlag) {
        //          vargs.add("-Xdebug -Xrunjdwp:transport=dt_socket,address=9998,server=y,suspend=y");
        //      }
        // Set class name 
        vargs.add(appMasterMainClass);
        // Set params for Application Master
        vargs.add("--container_memory " + String.valueOf(containerMemory));
        vargs.add("--num_containers " + String.valueOf(numContainers));
        vargs.add("--priority " + String.valueOf(shellCmdPriority));
        if (!shellCommand.isEmpty()) {
            vargs.add("--shell_command " + shellCommand + "");
        }
        if (!shellArgs.isEmpty()) {
            vargs.add("--shell_args " + shellArgs + "");
        }
        for (Map.Entry<String, String> entry : shellEnv.entrySet()) {
            vargs.add("--shell_env " + entry.getKey() + "=" + entry.getValue());
        }
        if (debugFlag) {
            vargs.add("--debug");
        }

        vargs.add("1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/AppMaster.stdout");
        vargs.add("2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/AppMaster.stderr");

        // Get final commmand
        StringBuilder command = new StringBuilder();
        for (CharSequence str : vargs) {
            command.append(str).append(" ");
        }

        LOG.info("Completed setting up app master command " + command.toString());
        List<String> commands = new ArrayList<String>();
        commands.add(command.toString());
        amContainer.setCommands(commands);

        // Set up resource type requirements
        // For now, only memory is supported so we set memory requirements
        Resource capability = Records.newRecord(Resource.class);
        capability.setMemory(amMemory);
        appContext.setResource(capability);

        // Service data is a binary blob that can be passed to the application
        // Not needed in this scenario
        // amContainer.setServiceData(serviceData);

        // Setup security tokens
        if (UserGroupInformation.isSecurityEnabled()) {
            Credentials credentials = new Credentials();
            String tokenRenewer = conf.get(YarnConfiguration.RM_PRINCIPAL);
            if (tokenRenewer == null || tokenRenewer.length() == 0) {
                throw new IOException("Can't get Master Kerberos principal for the RM to use as renewer");
            }

            // For now, only getting tokens for the default file-system.
            final Token<?> tokens[] = fs.addDelegationTokens(tokenRenewer, credentials);
            if (tokens != null) {
                for (Token<?> token : tokens) {
                    LOG.info("Got dt for " + fs.getUri() + "; " + token);
                }
            }
            DataOutputBuffer dob = new DataOutputBuffer();
            credentials.writeTokenStorageToStream(dob);
            ByteBuffer fsTokens = ByteBuffer.wrap(dob.getData(), 0, dob.getLength());
            amContainer.setTokens(fsTokens);
        }

        appContext.setAMContainerSpec(amContainer);

        // Set the priority for the application master
        Priority pri = Records.newRecord(Priority.class);
        // TODO - what is the range for priority? how to decide? 
        pri.setPriority(amPriority);
        appContext.setPriority(pri);

        // Set the queue to which this application is to be submitted in the RM
        appContext.setQueue(amQueue);

        // Submit the application to the applications manager
        // SubmitApplicationResponse submitResp = applicationsManager.submitApplication(appRequest);
        // Ignore the response as either a valid response object is returned on success 
        // or an exception thrown to denote some form of a failure
        LOG.info("Submitting application to ASM");

        yarnClient.submitApplication(appContext);

        // TODO
        // Try submitting the same request again
        // app submission failure?

        // Monitor the application
        return monitorApplication(appId);

    }

    /**
     * Monitor the submitted application for completion. 
     * Kill application if time expires. 
     * @param appId Application Id of application to be monitored
     * @return true if application completed successfully
     * @throws YarnException
     * @throws IOException
     */
    private boolean monitorApplication(ApplicationId appId) throws YarnException, IOException {

        while (true) {

            // Check app status every 1 second.
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                LOG.debug("Thread sleep in monitoring loop interrupted");
            }

            // Get application report for the appId we are interested in 
            ApplicationReport report = yarnClient.getApplicationReport(appId);

            LOG.info("Got application report from ASM for" + ", appId=" + appId.getId() + ", clientToAMToken="
                    + report.getClientToAMToken() + ", appDiagnostics=" + report.getDiagnostics()
                    + ", appMasterHost=" + report.getHost() + ", appQueue=" + report.getQueue()
                    + ", appMasterRpcPort=" + report.getRpcPort() + ", appStartTime=" + report.getStartTime()
                    + ", yarnAppState=" + report.getYarnApplicationState().toString() + ", distributedFinalState="
                    + report.getFinalApplicationStatus().toString() + ", appTrackingUrl=" + report.getTrackingUrl()
                    + ", appUser=" + report.getUser());

            YarnApplicationState state = report.getYarnApplicationState();
            FinalApplicationStatus dsStatus = report.getFinalApplicationStatus();
            if (YarnApplicationState.FINISHED == state) {
                if (FinalApplicationStatus.SUCCEEDED == dsStatus) {
                    LOG.info("Application has completed successfully. Breaking monitoring loop");
                    return true;
                } else {
                    LOG.info("Application did finished unsuccessfully." + " YarnState=" + state.toString()
                            + ", DSFinalStatus=" + dsStatus.toString() + ". Breaking monitoring loop");
                    return false;
                }
            } else if (YarnApplicationState.KILLED == state || YarnApplicationState.FAILED == state) {
                LOG.info("Application did not finish." + " YarnState=" + state.toString() + ", DSFinalStatus="
                        + dsStatus.toString() + ". Breaking monitoring loop");
                return false;
            }

            if (System.currentTimeMillis() > (clientStartTime + clientTimeout)) {
                LOG.info("Reached client specified timeout for application. Killing application");
                forceKillApplication(appId);
                return false;
            }
        }

    }

    /**
     * Kill a submitted application by sending a call to the ASM
     * @param appId Application Id to be killed. 
     * @throws YarnException
     * @throws IOException
     */
    private void forceKillApplication(ApplicationId appId) throws YarnException, IOException {
        // TODO clarify whether multiple jobs with the same app id can be submitted and be running at 
        // the same time. 
        // If yes, can we kill a particular attempt only?

        // Response can be ignored as it is non-null on success or 
        // throws an exception in case of failures
        yarnClient.killApplication(appId);
    }

}