YARN-5303. Clean up ContainerExecutor JavaDoc. Contributed by Daniel Templeton.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/ContainerExecutor.java

@@ -60,20 +60,31 @@
 import org.apache.hadoop.util.Shell;
 import org.apache.hadoop.util.StringUtils;
 
+/**
+ * This class is abstraction of the mechanism used to launch a container on the
+ * underlying OS.  All executor implementations must extend ContainerExecutor.
+ */
 public abstract class ContainerExecutor implements Configurable {
   private static final String WILDCARD = "*";
   private static final Log LOG = LogFactory.getLog(ContainerExecutor.class);
-  final public static FsPermission TASK_LAUNCH_SCRIPT_PERMISSION =
-    FsPermission.createImmutable((short) 0700);
 
+  /**
+   * The permissions to use when creating the launch script.
+   */
+  public static final FsPermission TASK_LAUNCH_SCRIPT_PERMISSION =
+      FsPermission.createImmutable((short)0700);
+
+  /**
+   * The relative path to which debug information will be written.
+   *
+   * @see ContainerLaunch.ShellScriptBuilder#listDebugInformation
+   */
   public static final String DIRECTORY_CONTENTS = "directory.info";
 
   private Configuration conf;
-
-  private ConcurrentMap<ContainerId, Path> pidFiles =
-      new ConcurrentHashMap<ContainerId, Path>();
-
-  private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
+  private final ConcurrentMap<ContainerId, Path> pidFiles =
+      new ConcurrentHashMap<>();
+  private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
   private final ReadLock readLock = lock.readLock();
   private final WriteLock writeLock = lock.writeLock();
 
@@ -88,30 +99,34 @@ public Configuration getConf() {
   }
 
   /**
-   * Run the executor initialization steps. 
-   * Verify that the necessary configs, permissions are in place.
-   * @throws IOException
+   * Run the executor initialization steps.
+   * Verify that the necessary configs and permissions are in place.
+   *
+   * @throws IOException if initialization fails
    */
   public abstract void init() throws IOException;
 
   /**
-   * On Windows the ContainerLaunch creates a temporary special jar manifest of 
-   * other jars to workaround the CLASSPATH length. In a  secure cluster this 
-   * jar must be localized so that the container has access to it. 
-   * This function localizes on-demand the jar.
-   * 
-   * @param classPathJar
-   * @param owner
-   * @throws IOException
+   * This function localizes the JAR file on-demand.
+   * On Windows the ContainerLaunch creates a temporary special JAR manifest of
+   * other JARs to workaround the CLASSPATH length. In a secure cluster this
+   * JAR must be localized so that the container has access to it.
+   * The default implementation returns the classpath passed to it, which
+   * is expected to have been created in the node manager's <i>fprivate</i>
+   * folder, which will not work with secure Windows clusters.
+   *
+   * @param jarPath the path to the JAR to localize
+   * @param target the directory where the JAR file should be localized
+   * @param owner the name of the user who should own the localized file
+   * @return the path to the localized JAR file
+   * @throws IOException if localization fails
    */
-  public Path localizeClasspathJar(Path classPathJar, Path pwd, String owner) 
+  public Path localizeClasspathJar(Path jarPath, Path target, String owner)
       throws IOException {
-    // Non-secure executor simply use the classpath created 
-    // in the NM fprivate folder
-    return classPathJar;
+    return jarPath;
   }
-  
-  
+
+
   /**
    * Prepare the environment for containers in this application to execute.
    * <pre>
@@ -123,10 +138,11 @@ public Path localizeClasspathJar(Path classPathJar, Path pwd, String owner)
    * For $rsrc in job resources
    *   Copy $rsrc {@literal ->} $N/$user/$appId/filecache/idef
    * </pre>
+   *
    * @param ctx LocalizerStartContext that encapsulates necessary information
    *            for starting a localizer.
-   * @throws IOException For most application init failures
-   * @throws InterruptedException If application init thread is halted by NM
+   * @throws IOException for most application init failures
+   * @throws InterruptedException if application init thread is halted by NM
    */
   public abstract void startLocalizer(LocalizerStartContext ctx)
     throws IOException, InterruptedException;
@@ -137,25 +153,28 @@ public abstract void startLocalizer(LocalizerStartContext ctx)
    * when the container exits.
    * @param ctx Encapsulates information necessary for launching containers.
    * @return the return status of the launch
-   * @throws IOException
+   * @throws IOException if the container launch fails
    */
   public abstract int launchContainer(ContainerStartContext ctx) throws
       IOException;
 
   /**
    * Signal container with the specified signal.
+   *
    * @param ctx Encapsulates information necessary for signaling containers.
    * @return returns true if the operation succeeded
-   * @throws IOException
+   * @throws IOException if signaling the container fails
    */
   public abstract boolean signalContainer(ContainerSignalContext ctx)
       throws IOException;
 
   /**
    * Delete specified directories as a given user.
+   *
    * @param ctx Encapsulates information necessary for deletion.
-   * @throws IOException
-   * @throws InterruptedException
+   * @throws IOException if delete fails
+   * @throws InterruptedException if interrupted while waiting for the deletion
+   * operation to complete
    */
   public abstract void deleteAsUser(DeletionAsUserContext ctx)
       throws IOException, InterruptedException;
@@ -164,7 +183,8 @@ public abstract void deleteAsUser(DeletionAsUserContext ctx)
    * Check if a container is alive.
    * @param ctx Encapsulates information necessary for container liveness check.
    * @return true if container is still alive
-   * @throws IOException
+   * @throws IOException if there is a failure while checking the container
+   * status
    */
   public abstract boolean isContainerAlive(ContainerLivenessContext ctx)
       throws IOException;
@@ -173,56 +193,63 @@ public abstract boolean isContainerAlive(ContainerLivenessContext ctx)
    * Recover an already existing container. This is a blocking call and returns
    * only when the container exits.  Note that the container must have been
    * activated prior to this call.
+   *
    * @param ctx encapsulates information necessary to reacquire container
    * @return The exit code of the pre-existing container
-   * @throws IOException
-   * @throws InterruptedException 
+   * @throws IOException if there is a failure while reacquiring the container
+   * @throws InterruptedException if interrupted while waiting to reacquire
+   * the container
    */
   public int reacquireContainer(ContainerReacquisitionContext ctx)
       throws IOException, InterruptedException {
     Container container = ctx.getContainer();
     String user = ctx.getUser();
     ContainerId containerId = ctx.getContainerId();
-
-
     Path pidPath = getPidFilePath(containerId);
+
     if (pidPath == null) {
       LOG.warn(containerId + " is not active, returning terminated error");
+
       return ExitCode.TERMINATED.getExitCode();
     }
 
-    String pid = null;
-    pid = ProcessIdFileReader.getProcessId(pidPath);
+    String pid = ProcessIdFileReader.getProcessId(pidPath);
+
     if (pid == null) {
       throw new IOException("Unable to determine pid for " + containerId);
     }
 
     LOG.info("Reacquiring " + containerId + " with pid " + pid);
+
     ContainerLivenessContext livenessContext = new ContainerLivenessContext
         .Builder()
         .setContainer(container)
         .setUser(user)
         .setPid(pid)
         .build();
-    while(isContainerAlive(livenessContext)) {
+
+    while (isContainerAlive(livenessContext)) {
       Thread.sleep(1000);
     }
 
     // wait for exit code file to appear
-    String exitCodeFile = ContainerLaunch.getExitCodeFile(pidPath.toString());
-    File file = new File(exitCodeFile);
     final int sleepMsec = 100;
     int msecLeft = 2000;
+    String exitCodeFile = ContainerLaunch.getExitCodeFile(pidPath.toString());
+    File file = new File(exitCodeFile);
+
     while (!file.exists() && msecLeft >= 0) {
       if (!isContainerActive(containerId)) {
         LOG.info(containerId + " was deactivated");
+
         return ExitCode.TERMINATED.getExitCode();
       }
-      
+
       Thread.sleep(sleepMsec);
-      
+
       msecLeft -= sleepMsec;
     }
+
     if (msecLeft < 0) {
       throw new IOException("Timeout while waiting for exit code from "
           + containerId);
@@ -236,15 +263,17 @@ public int reacquireContainer(ContainerReacquisitionContext ctx)
   }
 
   /**
-   * This method writes out the launch environment of a container. This can be
-   * overridden by extending ContainerExecutors to provide different behaviors
+   * This method writes out the launch environment of a container to the
+   * default container launch script. For the default container script path see
+   * {@link ContainerLaunch#CONTAINER_SCRIPT}.
+   *
    * @param out the output stream to which the environment is written (usually
    * a script file which will be executed by the Launcher)
-   * @param environment The environment variables and their values
-   * @param resources The resources which have been localized for this container
-   * Symlinks will be created to these localized resources
-   * @param command The command that will be run.
-   * @param logDir The log dir to copy debugging information to
+   * @param environment the environment variables and their values
+   * @param resources the resources which have been localized for this
+   * container. Symlinks will be created to these localized resources
+   * @param command the command that will be run.
+   * @param logDir the log dir to copy debugging information to
    * @throws IOException if any errors happened writing to the OutputStream,
    * while creating symlinks
    */
@@ -255,6 +284,21 @@ public void writeLaunchEnv(OutputStream out, Map<String, String> environment,
         ContainerLaunch.CONTAINER_SCRIPT);
   }
 
+  /**
+   * This method writes out the launch environment of a container to a specified
+   * path.
+   *
+   * @param out the output stream to which the environment is written (usually
+   * a script file which will be executed by the Launcher)
+   * @param environment the environment variables and their values
+   * @param resources the resources which have been localized for this
+   * container. Symlinks will be created to these localized resources
+   * @param command the command that will be run.
+   * @param logDir the log dir to copy debugging information to
+   * @param outFilename the path to which to write the launch environment
+   * @throws IOException if any errors happened writing to the OutputStream,
+   * while creating symlinks
+   */
   @VisibleForTesting
   public void writeLaunchEnv(OutputStream out,
       Map<String, String> environment, Map<Path, List<String>> resources,
@@ -262,52 +306,57 @@ public void writeLaunchEnv(OutputStream out,
       throws IOException {
     ContainerLaunch.ShellScriptBuilder sb =
       ContainerLaunch.ShellScriptBuilder.create();
-    Set<String> whitelist = new HashSet<String>();
+    Set<String> whitelist = new HashSet<>();
+
     whitelist.add(YarnConfiguration.NM_DOCKER_CONTAINER_EXECUTOR_IMAGE_NAME);
     whitelist.add(ApplicationConstants.Environment.HADOOP_YARN_HOME.name());
     whitelist.add(ApplicationConstants.Environment.HADOOP_COMMON_HOME.name());
     whitelist.add(ApplicationConstants.Environment.HADOOP_HDFS_HOME.name());
     whitelist.add(ApplicationConstants.Environment.HADOOP_CONF_DIR.name());
     whitelist.add(ApplicationConstants.Environment.JAVA_HOME.name());
+
     if (environment != null) {
       for (Map.Entry<String,String> env : environment.entrySet()) {
         if (!whitelist.contains(env.getKey())) {
-          sb.env(env.getKey().toString(), env.getValue().toString());
+          sb.env(env.getKey(), env.getValue());
         } else {
-          sb.whitelistedEnv(env.getKey().toString(), env.getValue().toString());
+          sb.whitelistedEnv(env.getKey(), env.getValue());
         }
       }
     }
+
     if (resources != null) {
-      for (Map.Entry<Path,List<String>> entry : resources.entrySet()) {
-        for (String linkName : entry.getValue()) {
+      for (Path path: resources.keySet()) {
+        for (String linkName: resources.get(path)) {
           if (new Path(linkName).getName().equals(WILDCARD)) {
             // If this is a wildcarded path, link to everything in the
             // directory from the working directory
-            File directory = new File(entry.getKey().toString());
+            File directory = new File(path.toString());
 
             for (File wildLink : directory.listFiles()) {
               sb.symlink(new Path(wildLink.toString()),
                   new Path(wildLink.getName()));
             }
           } else {
-            sb.symlink(entry.getKey(), new Path(linkName));
+            sb.symlink(path, new Path(linkName));
           }
         }
       }
     }
 
     // dump debugging information if configured
-    if (getConf() != null && getConf().getBoolean(
-        YarnConfiguration.NM_LOG_CONTAINER_DEBUG_INFO,
+    if (getConf() != null &&
+        getConf().getBoolean(YarnConfiguration.NM_LOG_CONTAINER_DEBUG_INFO,
         YarnConfiguration.DEFAULT_NM_LOG_CONTAINER_DEBUG_INFO)) {
-      sb.copyDebugInformation(new Path(outFilename), new Path(logDir, outFilename));
+      sb.copyDebugInformation(new Path(outFilename),
+          new Path(logDir, outFilename));
       sb.listDebugInformation(new Path(logDir, DIRECTORY_CONTENTS));
     }
 
     sb.command(command);
 
     PrintStream pout = null;
+
     try {
       pout = new PrintStream(out, false, "UTF-8");
       sb.write(pout);
@@ -318,17 +367,25 @@ public void writeLaunchEnv(OutputStream out,
     }
   }
 
+  /**
+   * The container exit code.
+   */
   public enum ExitCode {
     SUCCESS(0),
     FORCE_KILLED(137),
     TERMINATED(143),
     LOST(154);
+
     private final int code;
 
     private ExitCode(int exitCode) {
       this.code = exitCode;
     }
 
+    /**
+     * Get the exit code as an int.
+     * @return the exit code as an int
+     */
     public int getExitCode() {
       return code;
     }
@@ -343,25 +400,41 @@ public String toString() {
    * The constants for the signals.
    */
   public enum Signal {
-    NULL(0, "NULL"), QUIT(3, "SIGQUIT"), 
-    KILL(9, "SIGKILL"), TERM(15, "SIGTERM");
+    NULL(0, "NULL"),
+    QUIT(3, "SIGQUIT"),
+    KILL(9, "SIGKILL"),
+    TERM(15, "SIGTERM");
+
     private final int value;
     private final String str;
+
     private Signal(int value, String str) {
       this.str = str;
       this.value = value;
     }
+
+    /**
+     * Get the signal number.
+     * @return the signal number
+     */
     public int getValue() {
       return value;
     }
+
     @Override
     public String toString() {
       return str;
     }
   }
 
+  /**
+   * Log each line of the output string as INFO level log messages.
+   *
+   * @param output the output string to log
+   */
   protected void logOutput(String output) {
     String shExecOutput = output;
+
     if (shExecOutput != null) {
       for (String str : shExecOutput.split("\n")) {
         LOG.info(str);
@@ -371,7 +444,8 @@ protected void logOutput(String output) {
 
   /**
    * Get the pidFile of the container.
-   * @param containerId
+   *
+   * @param containerId the container ID
    * @return the path of the pid-file for the given containerId.
    */
   protected Path getPidFilePath(ContainerId containerId) {
@@ -383,81 +457,151 @@ protected Path getPidFilePath(ContainerId containerId) {
     }
   }
 
+  /**
+   * Return a command line to execute the given command in the OS shell.
+   * On Windows, the {code}groupId{code} parameter can be used to launch
+   * and associate the given GID with a process group. On
+   * non-Windows hosts, the {code}groupId{code} parameter is ignored.
+   *
+   * @param command the command to execute
+   * @param groupId the job owner's GID
+   * @param userName the job owner's username
+   * @param pidFile the path to the container's PID file
+   * @param conf the configuration
+   * @return the command line to execute
+   */
   protected String[] getRunCommand(String command, String groupId,
       String userName, Path pidFile, Configuration conf) {
     return getRunCommand(command, groupId, userName, pidFile, conf, null);
   }
-  
-  /** 
-   *  Return a command to execute the given command in OS shell.
-   *  On Windows, the passed in groupId can be used to launch
-   *  and associate the given groupId in a process group. On
-   *  non-Windows, groupId is ignored. 
+
+  /**
+   * Return a command line to execute the given command in the OS shell.
+   * On Windows, the {code}groupId{code} parameter can be used to launch
+   * and associate the given GID with a process group. On
+   * non-Windows hosts, the {code}groupId{code} parameter is ignored.
+   *
+   * @param command the command to execute
+   * @param groupId the job owner's GID for Windows. On other operating systems
+   * it is ignored.
+   * @param userName the job owner's username for Windows. On other operating
+   * systems it is ignored.
+   * @param pidFile the path to the container's PID file on Windows. On other
+   * operating systems it is ignored.
+   * @param conf the configuration
+   * @param resource on Windows this parameter controls memory and CPU limits.
+   * If null, no limits are set. On other operating systems it is ignored.
+   * @return the command line to execute
    */
   protected String[] getRunCommand(String command, String groupId,
       String userName, Path pidFile, Configuration conf, Resource resource) {
-    boolean containerSchedPriorityIsSet = false;
-    int containerSchedPriorityAdjustment = 
-        YarnConfiguration.DEFAULT_NM_CONTAINER_EXECUTOR_SCHED_PRIORITY;
-
-    if (conf.get(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY) != 
-        null) {
-      containerSchedPriorityIsSet = true;
-      containerSchedPriorityAdjustment = conf 
-          .getInt(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY, 
-          YarnConfiguration.DEFAULT_NM_CONTAINER_EXECUTOR_SCHED_PRIORITY);
-    }
-  
     if (Shell.WINDOWS) {
-      int cpuRate = -1;
-      int memory = -1;
-      if (resource != null) {
-        if (conf
-            .getBoolean(
-                YarnConfiguration.NM_WINDOWS_CONTAINER_MEMORY_LIMIT_ENABLED,
-                YarnConfiguration.DEFAULT_NM_WINDOWS_CONTAINER_MEMORY_LIMIT_ENABLED)) {
-          memory = (int) resource.getMemorySize();
-        }
-
-        if (conf.getBoolean(
-            YarnConfiguration.NM_WINDOWS_CONTAINER_CPU_LIMIT_ENABLED,
-            YarnConfiguration.DEFAULT_NM_WINDOWS_CONTAINER_CPU_LIMIT_ENABLED)) {
-          int containerVCores = resource.getVirtualCores();
-          int nodeVCores = NodeManagerHardwareUtils.getVCores(conf);
-          int nodeCpuPercentage =
-              NodeManagerHardwareUtils.getNodeCpuPercentage(conf);
-
-          float containerCpuPercentage =
-              (float) (nodeCpuPercentage * containerVCores) / nodeVCores;
-
-          // CPU should be set to a percentage * 100, e.g. 20% cpu rate limit
-          // should be set as 20 * 100.
-          cpuRate = Math.min(10000, (int) (containerCpuPercentage * 100));
-        }
-      }
-      return new String[] { Shell.getWinUtilsPath(), "task", "create", "-m",
-          String.valueOf(memory), "-c", String.valueOf(cpuRate), groupId,
-          "cmd /c " + command };
+      return getRunCommandForWindows(command, groupId, userName, pidFile,
+          conf, resource);
     } else {
-      List<String> retCommand = new ArrayList<String>();
-      if (containerSchedPriorityIsSet) {
-        retCommand.addAll(Arrays.asList("nice", "-n",
-            Integer.toString(containerSchedPriorityAdjustment)));
-      }
-      retCommand.addAll(Arrays.asList("bash", command));
-      return retCommand.toArray(new String[retCommand.size()]);
+      return getRunCommandForOther(command, conf);
     }
 
   }
 
   /**
-   * Is the container still active?
-   * @param containerId
-   * @return true if the container is active else false.
+   * Return a command line to execute the given command in the OS shell.
+   * The {code}groupId{code} parameter can be used to launch
+   * and associate the given GID with a process group.
+   *
+   * @param command the command to execute
+   * @param groupId the job owner's GID
+   * @param userName the job owner's username
+   * @param pidFile the path to the container's PID file
+   * @param conf the configuration
+   * @param resource this parameter controls memory and CPU limits.
+   * If null, no limits are set.
+   * @return the command line to execute
+   */
+  protected String[] getRunCommandForWindows(String command, String groupId,
+      String userName, Path pidFile, Configuration conf, Resource resource) {
+    int cpuRate = -1;
+    int memory = -1;
+
+    if (resource != null) {
+      if (conf.getBoolean(
+          YarnConfiguration.NM_WINDOWS_CONTAINER_MEMORY_LIMIT_ENABLED,
+          YarnConfiguration.DEFAULT_NM_WINDOWS_CONTAINER_MEMORY_LIMIT_ENABLED)) {
+        memory = (int)resource.getMemorySize();
+      }
+
+      if (conf.getBoolean(
+          YarnConfiguration.NM_WINDOWS_CONTAINER_CPU_LIMIT_ENABLED,
+          YarnConfiguration.DEFAULT_NM_WINDOWS_CONTAINER_CPU_LIMIT_ENABLED)) {
+        int containerVCores = resource.getVirtualCores();
+        int nodeVCores = NodeManagerHardwareUtils.getVCores(conf);
+        int nodeCpuPercentage =
+            NodeManagerHardwareUtils.getNodeCpuPercentage(conf);
+
+        float containerCpuPercentage =
+            (float)(nodeCpuPercentage * containerVCores) / nodeVCores;
+
+        // CPU should be set to a percentage * 100, e.g. 20% cpu rate limit
+        // should be set as 20 * 100.
+        cpuRate = Math.min(10000, (int)(containerCpuPercentage * 100));
+      }
+    }
+
+    return new String[] {
+        Shell.getWinUtilsPath(),
+        "task",
+        "create",
+        "-m",
+        String.valueOf(memory),
+        "-c",
+        String.valueOf(cpuRate),
+        groupId,
+        "cmd /c " + command
+    };
+  }
+
+  /**
+   * Return a command line to execute the given command in the OS shell.
+   *
+   * @param command the command to execute
+   * @param conf the configuration
+   * @return the command line to execute
+   */
+  protected String[] getRunCommandForOther(String command,
+      Configuration conf) {
+    List<String> retCommand = new ArrayList<>();
+    boolean containerSchedPriorityIsSet = false;
+    int containerSchedPriorityAdjustment =
+        YarnConfiguration.DEFAULT_NM_CONTAINER_EXECUTOR_SCHED_PRIORITY;
+
+    if (conf.get(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY) !=
+        null) {
+      containerSchedPriorityIsSet = true;
+      containerSchedPriorityAdjustment = conf
+          .getInt(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY,
+          YarnConfiguration.DEFAULT_NM_CONTAINER_EXECUTOR_SCHED_PRIORITY);
+    }
+
+    if (containerSchedPriorityIsSet) {
+      retCommand.addAll(Arrays.asList("nice", "-n",
+          Integer.toString(containerSchedPriorityAdjustment)));
+    }
+
+    retCommand.addAll(Arrays.asList("bash", command));
+
+    return retCommand.toArray(new String[retCommand.size()]);
+  }
+
+  /**
+   * Return whether the container is still active.
+   *
+   * @param containerId the target container's ID
+   * @return true if the container is active
    */
   protected boolean isContainerActive(ContainerId containerId) {
     try {
       readLock.lock();
+
       return (this.pidFiles.containsKey(containerId));
     } finally {
       readLock.unlock();
@@ -465,13 +609,11 @@ protected boolean isContainerActive(ContainerId containerId) {
   }
 
   /**
-   * Mark the container as active
-   * 
-   * @param containerId
-   *          the ContainerId
-   * @param pidFilePath
-   *          Path where the executor should write the pid of the launched
-   *          process
+   * Mark the container as active.
+   *
+   * @param containerId the container ID
+   * @param pidFilePath the path where the executor should write the PID
+   * of the launched process
    */
   public void activateContainer(ContainerId containerId, Path pidFilePath) {
     try {
@@ -483,9 +625,10 @@ public void activateContainer(ContainerId containerId, Path pidFilePath) {
   }
 
   /**
-   * Mark the container as inactive.
-   * Done iff the container is still active. Else treat it as
-   * a no-op
+   * Mark the container as inactive. For inactive containers this
+   * method has no effect.
+   *
+   * @param containerId the container ID
    */
   public void deactivateContainer(ContainerId containerId) {
     try {
@@ -497,46 +640,63 @@ public void deactivateContainer(ContainerId containerId) {
   }
 
   /**
-   * Get the process-identifier for the container
-   * 
-   * @param containerID
-   * @return the processid of the container if it has already launched,
-   *         otherwise return null
+   * Get the process-identifier for the container.
+   *
+   * @param containerID the container ID
+   * @return the process ID of the container if it has already launched,
+   * or null otherwise
    */
   public String getProcessId(ContainerId containerID) {
     String pid = null;
     Path pidFile = pidFiles.get(containerID);
-    if (pidFile == null) {
-      // This container isn't even launched yet.
-      return pid;
-    }
-    try {
-      pid = ProcessIdFileReader.getProcessId(pidFile);
-    } catch (IOException e) {
-      LOG.error("Got exception reading pid from pid-file " + pidFile, e);
+
+    // If PID is null, this container hasn't launched yet.
+    if (pidFile != null) {
+      try {
+        pid = ProcessIdFileReader.getProcessId(pidFile);
+      } catch (IOException e) {
+        LOG.error("Got exception reading pid from pid-file " + pidFile, e);
+      }
     }
+
     return pid;
   }
 
+  /**
+   * This class will signal a target container after a specified delay.
+   * @see #signalContainer
+   */
   public static class DelayedProcessKiller extends Thread {
-    private Container container;
+    private final Container container;
     private final String user;
     private final String pid;
     private final long delay;
     private final Signal signal;
     private final ContainerExecutor containerExecutor;
 
+    /**
+     * Basic constructor.
+     *
+     * @param container the container to signal
+     * @param user the user as whow to send the signal
+     * @param pid the PID of the container process
+     * @param delayMS the period of time to wait in millis before signaling
+     * the container
+     * @param signal the signal to send
+     * @param containerExecutor the executor to use to send the signal
+     */
     public DelayedProcessKiller(Container container, String user, String pid,
-        long delay, Signal signal, ContainerExecutor containerExecutor) {
+        long delayMS, Signal signal, ContainerExecutor containerExecutor) {
       this.container = container;
       this.user = user;
       this.pid = pid;
-      this.delay = delay;
+      this.delay = delayMS;
       this.signal = signal;
       this.containerExecutor = containerExecutor;
       setName("Task killer for " + pid);
       setDaemon(false);
     }
+
     @Override
     public void run() {
       try {
@@ -548,13 +708,13 @@ public void run() {
             .setSignal(signal)
             .build());
       } catch (InterruptedException e) {
-        return;
+        interrupt();
       } catch (IOException e) {
         String message = "Exception when user " + user + " killing task " + pid
             + " in DelayedProcessKiller: " + StringUtils.stringifyException(e);
         LOG.warn(message);
-        container.handle(new ContainerDiagnosticsUpdateEvent(container
-          .getContainerId(), message));
+        container.handle(new ContainerDiagnosticsUpdateEvent(
+            container.getContainerId(), message));
       }
     }
   }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java

@@ -60,7 +60,6 @@
 import org.apache.hadoop.yarn.server.nodemanager.executor.ContainerStartContext;
 import org.apache.hadoop.yarn.server.nodemanager.executor.DeletionAsUserContext;
 import org.apache.hadoop.yarn.server.nodemanager.executor.LocalizerStartContext;
-import org.apache.hadoop.yarn.util.ConverterUtils;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Optional;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DockerContainerExecutor.java

@@ -63,7 +63,6 @@
 import org.apache.hadoop.yarn.server.nodemanager.executor.ContainerStartContext;
 import org.apache.hadoop.yarn.server.nodemanager.executor.DeletionAsUserContext;
 import org.apache.hadoop.yarn.server.nodemanager.executor.LocalizerStartContext;
-import org.apache.hadoop.yarn.util.ConverterUtils;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/LinuxContainerExecutor.java

@@ -324,8 +324,7 @@ public int launchContainer(ContainerStartContext ctx) throws IOException {
 
     resourcesHandler.preExecute(containerId,
             container.getResource());
-    String resourcesOptions = resourcesHandler.getResourcesOption(
-            containerId);
+    String resourcesOptions = resourcesHandler.getResourcesOption(containerId);
     String tcCommandFile = null;
 
     try {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/WindowsSecureContainerExecutor.java

@@ -628,16 +628,16 @@ protected void setScriptExecutable(Path script, String owner)
   }
 
   @Override
-  public Path localizeClasspathJar(Path classPathJar, Path pwd, String owner) 
+  public Path localizeClasspathJar(Path jarPath, Path target, String owner) 
       throws IOException {
     if (LOG.isDebugEnabled()) {
       LOG.debug(String.format("localizeClasspathJar: %s %s o:%s", 
-          classPathJar, pwd, owner));
+          jarPath, target, owner));
     }
-    createDir(pwd,  new FsPermission(DIR_PERM), true, owner);
-    String fileName = classPathJar.getName();
-    Path dst = new Path(pwd, fileName);
-    Native.Elevated.move(classPathJar, dst, true);
+    createDir(target,  new FsPermission(DIR_PERM), true, owner);
+    String fileName = jarPath.getName();
+    Path dst = new Path(target, fileName);
+    Native.Elevated.move(jarPath, dst, true);
     Native.Elevated.chown(dst, owner, nodeManagerGroup);
     return dst;
   }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/launcher/ContainerLaunch.java

@@ -82,7 +82,6 @@
 import org.apache.hadoop.yarn.server.nodemanager.util.ProcessIdFileReader;
 import org.apache.hadoop.yarn.util.Apps;
 import org.apache.hadoop.yarn.util.AuxiliaryServiceHelper;
-import org.apache.hadoop.yarn.util.ConverterUtils;
 
 import com.google.common.annotations.VisibleForTesting;
 
@@ -835,7 +834,7 @@ public abstract void copyDebugInformation(Path src, Path dst)
         throws IOException;
 
     /**
-     * Method to dump debug information to the a target file. This method will
+     * Method to dump debug information to a target file. This method will
      * be called by ContainerExecutor when setting up the container launch
      * script.
      * @param output the file to which debug information is to be written