Hadoop：撰寫 YARN 應用程式

// set the application submission context
ApplicationSubmissionContext appContext = app.getApplicationSubmissionContext();
ApplicationId appId = appContext.getApplicationId();

appContext.setKeepContainersAcrossApplicationAttempts(keepContainers);
appContext.setApplicationName(appName);

// 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);
addToLocalResources(fs, appMasterJar, appMasterJarPath, appId.toString(),
    localResources, null);

// Set the log4j properties if needed
if (!log4jPropFile.isEmpty()) {
  addToLocalResources(fs, log4jPropFile, log4jPath, appId.toString(),
      localResources, null);
}

// 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.toString() + "/" + SCRIPT_PATH;
  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();
}

if (!shellCommand.isEmpty()) {
  addToLocalResources(fs, null, shellCommandPath, appId.toString(),
      localResources, shellCommand);
}

if (shellArgs.length > 0) {
  addToLocalResources(fs, null, shellArgsPath, appId.toString(),
      localResources, StringUtils.join(shellArgs, " "));
}

// 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));

// 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(ApplicationConstants.CLASS_PATH_SEPARATOR).append("./*");
for (String c : conf.getStrings(
    YarnConfiguration.YARN_APPLICATION_CLASSPATH,
    YarnConfiguration.DEFAULT_YARN_CROSS_PLATFORM_APPLICATION_CLASSPATH)) {
  classPathEnv.append(ApplicationConstants.CLASS_PATH_SEPARATOR);
  classPathEnv.append(c.trim());
}
classPathEnv.append(ApplicationConstants.CLASS_PATH_SEPARATOR).append(
  "./log4j.properties");

// 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");
// Set class name
vargs.add(appMasterMainClass);
// Set params for Application Master
vargs.add("--container_memory " + String.valueOf(containerMemory));
vargs.add("--container_vcores " + String.valueOf(containerVirtualCores));
vargs.add("--num_containers " + String.valueOf(numContainers));
vargs.add("--priority " + String.valueOf(shellCmdPriority));

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 command
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());

// Set up the container launch context for the application master
ContainerLaunchContext amContainer = ContainerLaunchContext.newInstance(
  localResources, env, commands, null, null, null);

// Set up resource type requirements
// For now, both memory and vcores are supported, so we set memory and
// vcores requirements
Resource capability = Resource.newInstance(amMemory, amVCores);
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()) {
  // Note: Credentials class is marked as LimitedPrivate for HDFS and MapReduce
  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 = Priority.newInstance(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);

yarnClient.submitApplication(appContext);

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

Map<String, String> envs = System.getenv();
String containerIdString =
    envs.get(ApplicationConstants.AM_CONTAINER_ID_ENV);
if (containerIdString == null) {
  // container id should always be set in the env by the framework
  throw new IllegalArgumentException(
      "ContainerId not set in the environment");
}
ContainerId containerId = ConverterUtils.toContainerId(containerIdString);
ApplicationAttemptId appAttemptID = containerId.getApplicationAttemptId();

  AMRMClientAsync.CallbackHandler allocListener = new RMCallbackHandler();
  amRMClient = AMRMClientAsync.createAMRMClientAsync(1000, allocListener);
  amRMClient.init(conf);
  amRMClient.start();

  containerListener = createNMCallbackHandler();
  nmClientAsync = new NMClientAsyncImpl(containerListener);
  nmClientAsync.init(conf);
  nmClientAsync.start();

// Register self with ResourceManager
// This will start heartbeating to the RM
appMasterHostname = NetUtils.getHostname();
RegisterApplicationMasterResponse response = amRMClient
    .registerApplicationMaster(appMasterHostname, appMasterRpcPort,
        appMasterTrackingUrl);

// Dump out information about cluster capability as seen by the
// resource manager
int maxMem = response.getMaximumResourceCapability().getMemory();
LOG.info("Max mem capability of resources in this cluster " + maxMem);

int maxVCores = response.getMaximumResourceCapability().getVirtualCores();
LOG.info("Max vcores capability of resources in this cluster " + maxVCores);

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

if (containerVirtualCores > maxVCores) {
  LOG.info("Container virtual cores specified above max threshold of  cluster."
    + " Using max value." + ", specified=" + containerVirtualCores + ", max="
    + maxVCores);
  containerVirtualCores = maxVCores;
}
List<Container> previousAMRunningContainers =
    response.getContainersFromPreviousAttempts();
LOG.info("Received " + previousAMRunningContainers.size()
        + " previous AM's running containers on AM registration.");

List<Container> previousAMRunningContainers =
    response.getContainersFromPreviousAttempts();
LOG.info("Received " + previousAMRunningContainers.size()
    + " previous AM's running containers on AM registration.");

int numTotalContainersToRequest =
    numTotalContainers - previousAMRunningContainers.size();
// Setup ask for containers from RM
// Send request for containers to RM
// Until we get our fully allocated quota, we keep on polling RM for
// containers
// Keep looping until all the containers are launched and shell script
// executed on them ( regardless of success/failure).
for (int i = 0; i < numTotalContainersToRequest; ++i) {
  ContainerRequest containerAsk = setupContainerAskForRM();
  amRMClient.addContainerRequest(containerAsk);
}

private ContainerRequest setupContainerAskForRM() {
  // setup requirements for hosts
  // using * as any host will do for the distributed shell app
  // set the priority for the request
  Priority pri = Priority.newInstance(requestPriority);

  // Set up resource type requirements
  // For now, memory and CPU are supported so we set memory and cpu requirements
  Resource capability = Resource.newInstance(containerMemory,
    containerVirtualCores);

  ContainerRequest request = new ContainerRequest(capability, null, null,
      pri);
  LOG.info("Requested container ask: " + request.toString());
  return request;
}

@Override
public void onContainersAllocated(List<Container> allocatedContainers) {
  LOG.info("Got response from RM for container ask, allocatedCnt="
      + allocatedContainers.size());
  numAllocatedContainers.addAndGet(allocatedContainers.size());
  for (Container allocatedContainer : allocatedContainers) {
    LaunchContainerRunnable runnableLaunchContainer =
        new LaunchContainerRunnable(allocatedContainer, containerListener);
    Thread launchThread = new Thread(runnableLaunchContainer);

    // 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.
    launchThreads.add(launchThread);
    launchThread.start();
  }
}

@Override
public float getProgress() {
  // set progress to deliver to RM on next heartbeat
  float progress = (float) numCompletedContainers.get()
      / numTotalContainers;
  return progress;
}

// Set the necessary command to execute on the allocated container
Vector<CharSequence> vargs = new Vector<CharSequence>(5);

// Set executable command
vargs.add(shellCommand);
// Set shell script path
if (!scriptPath.isEmpty()) {
  vargs.add(Shell.WINDOWS ? ExecBatScripStringtPath
    : ExecShellStringPath);
}

// Set args for the shell command if any
vargs.add(shellArgs);
// Add log redirect params
vargs.add("1>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stdout");
vargs.add("2>" + ApplicationConstants.LOG_DIR_EXPANSION_VAR + "/stderr");

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

List<String> commands = new ArrayList<String>();
commands.add(command.toString());

// Set up ContainerLaunchContext, setting local resource, environment,
// command and token for constructor.

// Note for tokens: Set up tokens for the container too. Today, for normal
// shell commands, the container in distribute-shell doesn't need any
// tokens. We are populating them mainly for NodeManagers to be able to
// download anyfiles in the distributed file-system. The tokens are
// otherwise also useful in cases, for e.g., when one is running a
// "hadoop dfs" command inside the distributed shell.
ContainerLaunchContext ctx = ContainerLaunchContext.newInstance(
  localResources, shellEnv, commands, null, allTokens.duplicate(), null);
containerListener.addContainer(container.getId(), container);
nmClientAsync.startContainerAsync(container, ctx);

try {
  amRMClient.unregisterApplicationMaster(appStatus, appMessage, null);
} catch (YarnException ex) {
  LOG.error("Failed to unregister application", ex);
} catch (IOException e) {
  LOG.error("Failed to unregister application", e);
}

amRMClient.stop();

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);
yarnClient.submitApplication(appCtx);