org.apache.hadoop.yarn.server.nodemanager.DockerContainerExecutor.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.apache.hadoop.yarn.server.nodemanager;

import static org.apache.hadoop.fs.CreateFlag.CREATE;
import static org.apache.hadoop.fs.CreateFlag.OVERWRITE;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.InetSocketAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Pattern;

import org.apache.commons.lang.math.RandomUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.CommonConfigurationKeys;
import org.apache.hadoop.fs.FileContext;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.UnsupportedFileSystemException;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.util.Shell;
import org.apache.hadoop.util.Shell.ShellCommandExecutor;
import org.apache.hadoop.util.StringUtils;
import org.apache.hadoop.yarn.api.ApplicationConstants;
import org.apache.hadoop.yarn.api.records.ContainerId;
import org.apache.hadoop.yarn.conf.YarnConfiguration;
import org.apache.hadoop.yarn.factory.providers.RecordFactoryProvider;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.Container;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.container.ContainerDiagnosticsUpdateEvent;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.launcher.ContainerLaunch;
import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ContainerLocalizer;
import org.apache.hadoop.yarn.server.nodemanager.executor.ContainerLivenessContext;
import org.apache.hadoop.yarn.server.nodemanager.executor.ContainerSignalContext;
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;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;

/**
 * This executor will launch and run tasks inside Docker containers. It
 * currently only supports simple authentication mode. It shares a lot of code
 * with the DefaultContainerExecutor (and it may make sense to pull out those
 * common pieces later).
 */
public class DockerContainerExecutor extends ContainerExecutor {
    private static final Log LOG = LogFactory.getLog(DockerContainerExecutor.class);
    //The name of the script file that will launch the Docker containers
    public static final String DOCKER_CONTAINER_EXECUTOR_SCRIPT = "docker_container_executor";
    //The name of the session script that the DOCKER_CONTAINER_EXECUTOR_SCRIPT
    //launches in turn
    public static final String DOCKER_CONTAINER_EXECUTOR_SESSION_SCRIPT = "docker_container_executor_session";

    //This validates that the image is a proper docker image and would not crash
    //docker. The image name is not allowed to contain spaces. e.g.
    //registry.somecompany.com:9999/containername:0.1 or
    //containername:0.1 or
    //containername
    public static final String DOCKER_IMAGE_PATTERN = "^(([\\w\\.-]+)(:\\d+)*\\/)?[\\w\\.:-]+$";

    private final FileContext lfs;
    private final Pattern dockerImagePattern;

    public DockerContainerExecutor() {
        try {
            this.lfs = FileContext.getLocalFSFileContext();
            this.dockerImagePattern = Pattern.compile(DOCKER_IMAGE_PATTERN);
        } catch (UnsupportedFileSystemException e) {
            throw new RuntimeException(e);
        }
    }

    protected void copyFile(Path src, Path dst, String owner) throws IOException {
        lfs.util().copy(src, dst);
    }

    @Override
    public void init() throws IOException {
        String auth = getConf().get(CommonConfigurationKeys.HADOOP_SECURITY_AUTHENTICATION);
        if (auth != null && !auth.equals("simple")) {
            throw new IllegalStateException("DockerContainerExecutor only works with simple authentication mode");
        }
        String dockerExecutor = getConf().get(YarnConfiguration.NM_DOCKER_CONTAINER_EXECUTOR_EXEC_NAME,
                YarnConfiguration.NM_DEFAULT_DOCKER_CONTAINER_EXECUTOR_EXEC_NAME);
        if (!new File(dockerExecutor).exists()) {
            throw new IllegalStateException("Invalid docker exec path: " + dockerExecutor);
        }
    }

    @Override
    public synchronized void startLocalizer(LocalizerStartContext ctx) throws IOException, InterruptedException {
        Path nmPrivateContainerTokensPath = ctx.getNmPrivateContainerTokens();
        InetSocketAddress nmAddr = ctx.getNmAddr();
        String user = ctx.getUser();
        String appId = ctx.getAppId();
        String locId = ctx.getLocId();
        String userFolder = ctx.getUserFolder();
        LocalDirsHandlerService dirsHandler = ctx.getDirsHandler();
        List<String> localDirs = dirsHandler.getLocalDirs();
        List<String> logDirs = dirsHandler.getLogDirs();

        ContainerLocalizer localizer = new ContainerLocalizer(lfs, user, appId, locId, getPaths(localDirs),
                RecordFactoryProvider.getRecordFactory(getConf()), user);

        createUserLocalDirs(localDirs, user, userFolder);
        createUserCacheDirs(localDirs, user, userFolder);
        createAppDirs(localDirs, user, appId, userFolder);
        createAppLogDirs(appId, logDirs, user);

        // randomly choose the local directory
        Path appStorageDir = getWorkingDir(localDirs, user, appId, userFolder);

        String tokenFn = String.format(ContainerLocalizer.TOKEN_FILE_NAME_FMT, locId);
        Path tokenDst = new Path(appStorageDir, tokenFn);
        copyFile(nmPrivateContainerTokensPath, tokenDst, user);
        LOG.info("Copying from " + nmPrivateContainerTokensPath + " to " + tokenDst);
        lfs.setWorkingDirectory(appStorageDir);
        LOG.info("CWD set to " + appStorageDir + " = " + lfs.getWorkingDirectory());
        // TODO: DO it over RPC for maintaining similarity?
        localizer.runLocalization(nmAddr);
    }

    @Override
    public void recoverDeviceControlSystem(ContainerId containerId) {
        LOG.info("Device recovery is not supported for docker");
    }

    @Override
    public int launchContainer(ContainerStartContext ctx) throws IOException {
        Container container = ctx.getContainer();
        Path nmPrivateContainerScriptPath = ctx.getNmPrivateContainerScriptPath();
        Path nmPrivateTokensPath = ctx.getNmPrivateTokensPath();
        String userName = ctx.getUser();
        String userFolder = ctx.getUserFolder();
        Path containerWorkDir = ctx.getContainerWorkDir();
        List<String> localDirs = ctx.getLocalDirs();
        List<String> logDirs = ctx.getLogDirs();

        //Variables for the launch environment can be injected from the command-line
        //while submitting the application
        String containerImageName = container.getLaunchContext().getEnvironment()
                .get(YarnConfiguration.NM_DOCKER_CONTAINER_EXECUTOR_IMAGE_NAME);
        if (LOG.isDebugEnabled()) {
            LOG.debug("containerImageName from launchContext: " + containerImageName);
        }
        Preconditions.checkArgument(!Strings.isNullOrEmpty(containerImageName), "Container image must not be null");
        containerImageName = containerImageName.replaceAll("['\"]", "");

        Preconditions.checkArgument(saneDockerImage(containerImageName),
                "Image: " + containerImageName + " is not a proper docker image");
        String dockerExecutor = getConf().get(YarnConfiguration.NM_DOCKER_CONTAINER_EXECUTOR_EXEC_NAME,
                YarnConfiguration.NM_DEFAULT_DOCKER_CONTAINER_EXECUTOR_EXEC_NAME);

        FsPermission dirPerm = new FsPermission(APPDIR_PERM);
        ContainerId containerId = container.getContainerId();

        // create container dirs on all disks
        String containerIdStr = containerId.toString();
        String appIdStr = containerId.getApplicationAttemptId().getApplicationId().toString();
        for (String sLocalDir : localDirs) {
            Path usersdir = new Path(sLocalDir, ContainerLocalizer.USERCACHE);
            Path userdir = new Path(usersdir, userFolder);
            Path appCacheDir = new Path(userdir, ContainerLocalizer.APPCACHE);
            Path appDir = new Path(appCacheDir, appIdStr);
            Path containerDir = new Path(appDir, containerIdStr);
            createDir(containerDir, dirPerm, true, userName);
        }

        // Create the container log-dirs on all disks
        createContainerLogDirs(appIdStr, containerIdStr, logDirs, userName);

        Path tmpDir = new Path(containerWorkDir, YarnConfiguration.DEFAULT_CONTAINER_TEMP_DIR);
        createDir(tmpDir, dirPerm, false, userName);

        // copy launch script to work dir
        Path launchDst = new Path(containerWorkDir, ContainerLaunch.CONTAINER_SCRIPT);
        lfs.util().copy(nmPrivateContainerScriptPath, launchDst);

        // copy container tokens to work dir
        Path tokenDst = new Path(containerWorkDir, ContainerLaunch.FINAL_CONTAINER_TOKENS_FILE);
        lfs.util().copy(nmPrivateTokensPath, tokenDst);

        String localDirMount = toMount(localDirs);
        String logDirMount = toMount(logDirs);
        String containerWorkDirMount = toMount(Collections.singletonList(containerWorkDir.toUri().getPath()));
        StringBuilder commands = new StringBuilder();
        //Use docker run to launch the docker container. See man pages for
        //docker-run
        //--rm removes the container automatically once the container finishes
        //--net=host allows the container to take on the host's network stack
        //--name sets the Docker Container name to the YARN containerId string
        //-v is used to bind mount volumes for local, log and work dirs.
        String commandStr = commands.append(dockerExecutor).append(" ").append("run").append(" ")
                .append("--rm --net=host").append(" ").append(" --name " + containerIdStr).append(localDirMount)
                .append(logDirMount).append(containerWorkDirMount).append(" ").append(containerImageName)
                .toString();
        //Get the pid of the process which has been launched as a docker container
        //using docker inspect
        String dockerPidScript = "`" + dockerExecutor + " inspect --format {{.State.Pid}} " + containerIdStr + "`";

        // Create new local launch wrapper script
        LocalWrapperScriptBuilder sb = new UnixLocalWrapperScriptBuilder(containerWorkDir, commandStr,
                dockerPidScript);
        Path pidFile = getPidFilePath(containerId);
        if (pidFile != null) {
            sb.writeLocalWrapperScript(launchDst, pidFile);
        } else {
            //Although the container was activated by ContainerLaunch before exec()
            //was called, since then deactivateContainer() has been called.
            LOG.info("Container " + containerIdStr + " was marked as inactive. Returning terminated error");
            return ExitCode.TERMINATED.getExitCode();
        }

        ShellCommandExecutor shExec = null;
        try {
            lfs.setPermission(launchDst, ContainerExecutor.TASK_LAUNCH_SCRIPT_PERMISSION);
            lfs.setPermission(sb.getWrapperScriptPath(), ContainerExecutor.TASK_LAUNCH_SCRIPT_PERMISSION);

            // Setup command to run
            String[] command = getRunCommand(sb.getWrapperScriptPath().toString(), containerIdStr, userName,
                    pidFile, this.getConf());
            if (LOG.isDebugEnabled()) {
                LOG.debug("launchContainer: " + commandStr + " " + Joiner.on(" ").join(command));
            }
            shExec = new ShellCommandExecutor(command, new File(containerWorkDir.toUri().getPath()),
                    container.getLaunchContext().getEnvironment(), // sanitized env
                    0L, false);
            if (isContainerActive(containerId)) {
                shExec.execute();
            } else {
                LOG.info("Container " + containerIdStr + " was marked as inactive. Returning terminated error");
                return ExitCode.TERMINATED.getExitCode();
            }
        } catch (IOException e) {
            if (null == shExec) {
                return -1;
            }
            int exitCode = shExec.getExitCode();
            LOG.warn("Exit code from container " + containerId + " is : " + exitCode);
            // 143 (SIGTERM) and 137 (SIGKILL) exit codes means the container was
            // terminated/killed forcefully. In all other cases, log the
            // container-executor's output
            if (exitCode != ExitCode.FORCE_KILLED.getExitCode() && exitCode != ExitCode.TERMINATED.getExitCode()) {
                LOG.warn("Exception from container-launch with container ID: " + containerId + " and exit code: "
                        + exitCode, e);
                logOutput(shExec.getOutput());
                String diagnostics = "Exception from container-launch: \n" + StringUtils.stringifyException(e)
                        + "\n" + shExec.getOutput();
                container.handle(new ContainerDiagnosticsUpdateEvent(containerId, diagnostics));
            } else {
                container.handle(new ContainerDiagnosticsUpdateEvent(containerId,
                        "Container killed on request. Exit code is " + exitCode));
            }
            return exitCode;
        } finally {
            if (shExec != null) {
                shExec.close();
            }
        }
        return 0;
    }

    @Override
    /**
     * Filter the environment variables that may conflict with the ones set in
     * the docker image and write them out to an OutputStream.
     */
    public void writeLaunchEnv(OutputStream out, Map<String, String> environment, Map<Path, List<String>> resources,
            List<String> command, Path logDir) throws IOException {
        ContainerLaunch.ShellScriptBuilder sb = ContainerLaunch.ShellScriptBuilder.create();

        //Remove environments that may conflict with the ones in Docker image.
        Set<String> exclusionSet = new HashSet<String>();
        exclusionSet.add(YarnConfiguration.NM_DOCKER_CONTAINER_EXECUTOR_IMAGE_NAME);
        exclusionSet.add(ApplicationConstants.Environment.HADOOP_YARN_HOME.name());
        exclusionSet.add(ApplicationConstants.Environment.HADOOP_COMMON_HOME.name());
        exclusionSet.add(ApplicationConstants.Environment.HADOOP_HDFS_HOME.name());
        exclusionSet.add(ApplicationConstants.Environment.HADOOP_CONF_DIR.name());
        exclusionSet.add(ApplicationConstants.Environment.JAVA_HOME.name());

        if (environment != null) {
            for (Map.Entry<String, String> env : environment.entrySet()) {
                if (!exclusionSet.contains(env.getKey())) {
                    sb.env(env.getKey().toString(), env.getValue().toString());
                }
            }
        }
        if (resources != null) {
            for (Map.Entry<Path, List<String>> entry : resources.entrySet()) {
                for (String linkName : entry.getValue()) {
                    sb.symlink(entry.getKey(), new Path(linkName));
                }
            }
        }

        // dump debugging information if configured
        if (getConf() != null && getConf().getBoolean(YarnConfiguration.NM_LOG_CONTAINER_DEBUG_INFO,
                YarnConfiguration.DEFAULT_NM_LOG_CONTAINER_DEBUG_INFO)) {
            sb.copyDebugInformation(new Path(ContainerLaunch.CONTAINER_SCRIPT),
                    new Path(logDir, ContainerLaunch.CONTAINER_SCRIPT));
            sb.listDebugInformation(new Path(logDir, DIRECTORY_CONTENTS));
        }

        sb.command(command);

        PrintStream pout = null;
        PrintStream ps = null;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            pout = new PrintStream(out, false, "UTF-8");
            if (LOG.isDebugEnabled()) {
                ps = new PrintStream(baos, false, "UTF-8");
                sb.write(ps);
            }
            sb.write(pout);

        } finally {
            if (out != null) {
                out.close();
            }
            if (ps != null) {
                ps.close();
            }
        }
        if (LOG.isDebugEnabled()) {
            LOG.debug("Script: " + baos.toString("UTF-8"));
        }
    }

    private boolean saneDockerImage(String containerImageName) {
        return dockerImagePattern.matcher(containerImageName).matches();
    }

    @Override
    public boolean signalContainer(ContainerSignalContext ctx) throws IOException {
        String user = ctx.getUser();
        String pid = ctx.getPid();
        Signal signal = ctx.getSignal();

        if (LOG.isDebugEnabled()) {
            LOG.debug("Sending signal " + signal.getValue() + " to pid " + pid + " as user " + user);
        }
        if (!containerIsAlive(pid)) {
            return false;
        }
        try {
            killContainer(pid, signal);
        } catch (IOException e) {
            if (!containerIsAlive(pid)) {
                return false;
            }
            throw e;
        }
        return true;
    }

    @Override
    public boolean isContainerAlive(ContainerLivenessContext ctx) throws IOException {
        String pid = ctx.getPid();

        return containerIsAlive(pid);
    }

    /**
     * Returns true if the process with the specified pid is alive.
     *
     * @param pid String pid
     * @return boolean true if the process is alive
     */
    @VisibleForTesting
    public static boolean containerIsAlive(String pid) throws IOException {
        try {
            new ShellCommandExecutor(Shell.getCheckProcessIsAliveCommand(pid)).execute();
            // successful execution means process is alive
            return true;
        } catch (Shell.ExitCodeException e) {
            // failure (non-zero exit code) means process is not alive
            return false;
        }
    }

    /**
     * Send a specified signal to the specified pid
     *
     * @param pid the pid of the process [group] to signal.
     * @param signal signal to send
     * (for logging).
     */
    protected void killContainer(String pid, Signal signal) throws IOException {
        new ShellCommandExecutor(Shell.getSignalKillCommand(signal.getValue(), pid)).execute();
    }

    @Override
    public void deleteAsUser(DeletionAsUserContext ctx) throws IOException, InterruptedException {
        Path subDir = ctx.getSubDir();
        List<Path> baseDirs = ctx.getBasedirs();

        if (baseDirs == null || baseDirs.size() == 0) {
            LOG.info("Deleting absolute path : " + subDir);
            if (!lfs.delete(subDir, true)) {
                //Maybe retry
                LOG.warn("delete returned false for path: [" + subDir + "]");
            }
            return;
        }
        for (Path baseDir : baseDirs) {
            Path del = subDir == null ? baseDir : new Path(baseDir, subDir);
            LOG.info("Deleting path : " + del);
            try {
                if (!lfs.delete(del, true)) {
                    LOG.warn("delete returned false for path: [" + del + "]");
                }
            } catch (FileNotFoundException e) {
                continue;
            }
        }
    }

    /**
     * Converts a directory list to a docker mount string
     * @param dirs
     * @return a string of mounts for docker
     */
    private String toMount(List<String> dirs) {
        StringBuilder builder = new StringBuilder();
        for (String dir : dirs) {
            builder.append(" -v " + dir + ":" + dir);
        }
        return builder.toString();
    }

    //This class facilitates (only) the creation of platform-specific scripts that
    //will be used to launch the containers
    //TODO: This should be re-used from the DefaultContainerExecutor.
    private abstract class LocalWrapperScriptBuilder {

        private final Path wrapperScriptPath;

        public Path getWrapperScriptPath() {
            return wrapperScriptPath;
        }

        public void writeLocalWrapperScript(Path launchDst, Path pidFile) throws IOException {
            DataOutputStream out = null;
            PrintStream pout = null;

            try {
                out = lfs.create(wrapperScriptPath, EnumSet.of(CREATE, OVERWRITE));
                pout = new PrintStream(out, false, "UTF-8");
                writeLocalWrapperScript(launchDst, pidFile, pout);
            } finally {
                IOUtils.cleanup(LOG, pout, out);
            }
        }

        protected abstract void writeLocalWrapperScript(Path launchDst, Path pidFile, PrintStream pout);

        protected LocalWrapperScriptBuilder(Path containerWorkDir) {
            this.wrapperScriptPath = new Path(containerWorkDir,
                    Shell.appendScriptExtension(DOCKER_CONTAINER_EXECUTOR_SCRIPT));
        }
    }

    //TODO: This class too should be used from DefaultContainerExecutor.
    private final class UnixLocalWrapperScriptBuilder extends LocalWrapperScriptBuilder {
        private final Path sessionScriptPath;
        private final String dockerCommand;
        private final String dockerPidScript;

        public UnixLocalWrapperScriptBuilder(Path containerWorkDir, String dockerCommand, String dockerPidScript) {
            super(containerWorkDir);
            this.dockerCommand = dockerCommand;
            this.dockerPidScript = dockerPidScript;
            this.sessionScriptPath = new Path(containerWorkDir,
                    Shell.appendScriptExtension(DOCKER_CONTAINER_EXECUTOR_SESSION_SCRIPT));
        }

        @Override
        public void writeLocalWrapperScript(Path launchDst, Path pidFile) throws IOException {
            writeSessionScript(launchDst, pidFile);
            super.writeLocalWrapperScript(launchDst, pidFile);
        }

        @Override
        public void writeLocalWrapperScript(Path launchDst, Path pidFile, PrintStream pout) {
            String exitCodeFile = ContainerLaunch.getExitCodeFile(pidFile.toString());
            String tmpFile = exitCodeFile + ".tmp";
            pout.println("#!/usr/bin/env bash");
            pout.println("bash \"" + sessionScriptPath.toString() + "\"");
            pout.println("rc=$?");
            pout.println("echo $rc > \"" + tmpFile + "\"");
            pout.println("mv -f \"" + tmpFile + "\" \"" + exitCodeFile + "\"");
            pout.println("exit $rc");
        }

        private void writeSessionScript(Path launchDst, Path pidFile) throws IOException {
            DataOutputStream out = null;
            PrintStream pout = null;
            try {
                out = lfs.create(sessionScriptPath, EnumSet.of(CREATE, OVERWRITE));
                pout = new PrintStream(out, false, "UTF-8");
                // We need to do a move as writing to a file is not atomic
                // Process reading a file being written to may get garbled data
                // hence write pid to tmp file first followed by a mv
                pout.println("#!/usr/bin/env bash");
                pout.println();
                pout.println("echo " + dockerPidScript + " > " + pidFile.toString() + ".tmp");
                pout.println("/bin/mv -f " + pidFile.toString() + ".tmp " + pidFile);
                pout.println(dockerCommand + " bash \"" + launchDst.toUri().getPath().toString() + "\"");
            } finally {
                IOUtils.cleanup(LOG, pout, out);
            }
            lfs.setPermission(sessionScriptPath, ContainerExecutor.TASK_LAUNCH_SCRIPT_PERMISSION);
        }
    }

    protected void createDir(Path dirPath, FsPermission perms, boolean createParent, String user)
            throws IOException {
        lfs.mkdir(dirPath, perms, createParent);
        if (!perms.equals(perms.applyUMask(lfs.getUMask()))) {
            lfs.setPermission(dirPath, perms);
        }
    }

    /**
     * Initialize the local directories for a particular user.
     * <ul>.mkdir
     * <li>$local.dir/usercache/$user</li>
     * </ul>
     */
    void createUserLocalDirs(List<String> localDirs, String user, String userFolder) throws IOException {
        boolean userDirStatus = false;
        FsPermission userperms = new FsPermission(USER_PERM);
        for (String localDir : localDirs) {
            // create $local.dir/usercache/$user and its immediate parent
            try {
                createDir(getUserCacheDir(new Path(localDir), userFolder), userperms, true, user);
            } catch (IOException e) {
                LOG.warn("Unable to create the user directory : " + localDir, e);
                continue;
            }
            userDirStatus = true;
        }
        if (!userDirStatus) {
            throw new IOException("Not able to initialize user directories "
                    + "in any of the configured local directories for user " + user);
        }
    }

    /**
     * Initialize the local cache directories for a particular user.
     * <ul>
     * <li>$local.dir/usercache/$user</li>
     * <li>$local.dir/usercache/$user/appcache</li>
     * <li>$local.dir/usercache/$user/filecache</li>
     * </ul>
     */
    void createUserCacheDirs(List<String> localDirs, String user, String userFolder) throws IOException {
        LOG.info("Initializing user " + user);

        boolean appcacheDirStatus = false;
        boolean distributedCacheDirStatus = false;
        FsPermission appCachePerms = new FsPermission(APPCACHE_PERM);
        FsPermission fileperms = new FsPermission(FILECACHE_PERM);

        for (String localDir : localDirs) {
            // create $local.dir/usercache/$user/appcache
            Path localDirPath = new Path(localDir);
            final Path appDir = getAppcacheDir(localDirPath, userFolder);
            try {
                createDir(appDir, appCachePerms, true, user);
                appcacheDirStatus = true;
            } catch (IOException e) {
                LOG.warn("Unable to create app cache directory : " + appDir, e);
            }
            // create $local.dir/usercache/$user/filecache
            final Path distDir = getFileCacheDir(localDirPath, userFolder);
            try {
                createDir(distDir, fileperms, true, user);
                distributedCacheDirStatus = true;
            } catch (IOException e) {
                LOG.warn("Unable to create file cache directory : " + distDir, e);
            }
        }
        if (!appcacheDirStatus) {
            throw new IOException("Not able to initialize app-cache directories "
                    + "in any of the configured local directories for user " + user);
        }
        if (!distributedCacheDirStatus) {
            throw new IOException("Not able to initialize distributed-cache directories "
                    + "in any of the configured local directories for user " + user);
        }
    }

    /**
     * Initialize the local directories for a particular user.
     * <ul>
     * <li>$local.dir/usercache/$user/appcache/$appid</li>
     * </ul>
     * @param localDirs
     */
    void createAppDirs(List<String> localDirs, String user, String appId, String userFolder) throws IOException {
        boolean initAppDirStatus = false;
        FsPermission appperms = new FsPermission(APPDIR_PERM);
        for (String localDir : localDirs) {
            Path fullAppDir = getApplicationDir(new Path(localDir), userFolder, appId);
            // create $local.dir/usercache/$user/appcache/$appId
            try {
                createDir(fullAppDir, appperms, true, user);
                initAppDirStatus = true;
            } catch (IOException e) {
                LOG.warn("Unable to create app directory " + fullAppDir.toString(), e);
            }
        }
        if (!initAppDirStatus) {
            throw new IOException("Not able to initialize app directories "
                    + "in any of the configured local directories for app " + appId.toString());
        }
    }

    /**
     * Create application log directories on all disks.
     */
    void createContainerLogDirs(String appId, String containerId, List<String> logDirs, String user)
            throws IOException {

        boolean containerLogDirStatus = false;
        FsPermission containerLogDirPerms = new FsPermission(LOGDIR_PERM);
        for (String rootLogDir : logDirs) {
            // create $log.dir/$appid/$containerid
            Path appLogDir = new Path(rootLogDir, appId);
            Path containerLogDir = new Path(appLogDir, containerId);
            try {
                createDir(containerLogDir, containerLogDirPerms, true, user);
            } catch (IOException e) {
                LOG.warn("Unable to create the container-log directory : " + appLogDir, e);
                continue;
            }
            containerLogDirStatus = true;
        }
        if (!containerLogDirStatus) {
            throw new IOException("Not able to initialize container-log directories "
                    + "in any of the configured local directories for container " + containerId);
        }
    }

    /**
     * Permissions for user dir.
     * $local.dir/usercache/$user
     */
    static final short USER_PERM = (short) 0750;
    /**
     * Permissions for user appcache dir.
     * $local.dir/usercache/$user/appcache
     */
    static final short APPCACHE_PERM = (short) 0710;
    /**
     * Permissions for user filecache dir.
     * $local.dir/usercache/$user/filecache
     */
    static final short FILECACHE_PERM = (short) 0710;
    /**
     * Permissions for user app dir.
     * $local.dir/usercache/$user/appcache/$appId
     */
    static final short APPDIR_PERM = (short) 0710;
    /**
     * Permissions for user log dir.
     * $logdir/$user/$appId
     */
    static final short LOGDIR_PERM = (short) 0710;

    private long getDiskFreeSpace(Path base) throws IOException {
        return lfs.getFsStatus(base).getRemaining();
    }

    private Path getApplicationDir(Path base, String userFolder, String appId) {
        return new Path(getAppcacheDir(base, userFolder), appId);
    }

    private Path getUserCacheDir(Path base, String userFolder) {
        return new Path(new Path(base, ContainerLocalizer.USERCACHE), userFolder);
    }

    private Path getAppcacheDir(Path base, String userFolder) {
        return new Path(getUserCacheDir(base, userFolder), ContainerLocalizer.APPCACHE);
    }

    private Path getFileCacheDir(Path base, String userFolder) {
        return new Path(getUserCacheDir(base, userFolder), ContainerLocalizer.FILECACHE);
    }

    protected Path getWorkingDir(List<String> localDirs, String user, String appId, String userFolder)
            throws IOException {
        Path appStorageDir = null;
        long totalAvailable = 0L;
        long[] availableOnDisk = new long[localDirs.size()];
        int i = 0;
        // randomly choose the app directory
        // the chance of picking a directory is proportional to
        // the available space on the directory.
        // firstly calculate the sum of all available space on these directories
        for (String localDir : localDirs) {
            Path curBase = getApplicationDir(new Path(localDir), userFolder, appId);
            long space = 0L;
            try {
                space = getDiskFreeSpace(curBase);
            } catch (IOException e) {
                LOG.warn("Unable to get Free Space for " + curBase.toString(), e);
            }
            availableOnDisk[i++] = space;
            totalAvailable += space;
        }

        // throw an IOException if totalAvailable is 0.
        if (totalAvailable <= 0L) {
            throw new IOException("Not able to find a working directory for " + user);
        }

        // make probability to pick a directory proportional to
        // the available space on the directory.
        long randomPosition = RandomUtils.nextLong() % totalAvailable;
        int dir = 0;
        // skip zero available space directory,
        // because totalAvailable is greater than 0 and randomPosition
        // is less than totalAvailable, we can find a valid directory
        // with nonzero available space.
        while (availableOnDisk[dir] == 0L) {
            dir++;
        }
        while (randomPosition > availableOnDisk[dir]) {
            randomPosition -= availableOnDisk[dir++];
        }
        appStorageDir = getApplicationDir(new Path(localDirs.get(dir)), userFolder, appId);

        return appStorageDir;
    }

    /**
     * Create application log directories on all disks.
     */
    void createAppLogDirs(String appId, List<String> logDirs, String user) throws IOException {

        boolean appLogDirStatus = false;
        FsPermission appLogDirPerms = new FsPermission(LOGDIR_PERM);
        for (String rootLogDir : logDirs) {
            // create $log.dir/$appid
            Path appLogDir = new Path(rootLogDir, appId);
            try {
                createDir(appLogDir, appLogDirPerms, true, user);
            } catch (IOException e) {
                LOG.warn("Unable to create the app-log directory : " + appLogDir, e);
                continue;
            }
            appLogDirStatus = true;
        }
        if (!appLogDirStatus) {
            throw new IOException("Not able to initialize app-log directories "
                    + "in any of the configured local directories for app " + appId);
        }
    }

    /**
     * @return the list of paths of given local directories
     */
    private static List<Path> getPaths(List<String> dirs) {
        List<Path> paths = new ArrayList<Path>(dirs.size());
        for (int i = 0; i < dirs.size(); i++) {
            paths.add(new Path(dirs.get(i)));
        }
        return paths;
    }

}