Java tutorial
/** * 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 com.buaa.cfs.utils; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.io.*; import java.nio.charset.Charset; import java.util.Arrays; import java.util.Map; import java.util.Timer; import java.util.TimerTask; import java.util.concurrent.atomic.AtomicBoolean; /** * A base class for running a Unix command. * * <code>Shell</code> can be used to run unix commands like <code>du</code> or * <code>df</code>. It also offers facilities to gate commands by * time-intervals. */ abstract public class Shell { public static final Log LOG = LogFactory.getLog(Shell.class); private static boolean IS_JAVA7_OR_ABOVE = System.getProperty("java.version").substring(0, 3) .compareTo("1.7") >= 0; public static boolean isJava7OrAbove() { return IS_JAVA7_OR_ABOVE; } /** * Maximum command line length in Windows * KB830473 documents this as 8191 */ public static final int WINDOWS_MAX_SHELL_LENGHT = 8191; /** * Checks if a given command (String[]) fits in the Windows maximum command line length * Note that the input is expected to already include space delimiters, no extra count * will be added for delimiters. * * @param commands command parts, including any space delimiters */ public static void checkWindowsCommandLineLength(String... commands) throws IOException { int len = 0; for (String s : commands) { len += s.length(); } if (len > WINDOWS_MAX_SHELL_LENGHT) { throw new IOException(String.format( "The command line has a length of %d exceeds maximum allowed length of %d. " + "Command starts with: %s", len, WINDOWS_MAX_SHELL_LENGHT, StringUtils.join("", commands).substring(0, 100))); } } /** a Unix command to get the current user's name */ public final static String USER_NAME_COMMAND = "whoami"; /** Windows CreateProcess synchronization object */ public static final Object WindowsProcessLaunchLock = new Object(); // OSType detection public enum OSType { OS_TYPE_LINUX, OS_TYPE_WIN, OS_TYPE_SOLARIS, OS_TYPE_MAC, OS_TYPE_FREEBSD, OS_TYPE_OTHER } public static final OSType osType = getOSType(); static private OSType getOSType() { String osName = System.getProperty("os.name"); if (osName.startsWith("Windows")) { return OSType.OS_TYPE_WIN; } else if (osName.contains("SunOS") || osName.contains("Solaris")) { return OSType.OS_TYPE_SOLARIS; } else if (osName.contains("Mac")) { return OSType.OS_TYPE_MAC; } else if (osName.contains("FreeBSD")) { return OSType.OS_TYPE_FREEBSD; } else if (osName.startsWith("Linux")) { return OSType.OS_TYPE_LINUX; } else { // Some other form of Unix return OSType.OS_TYPE_OTHER; } } // Helper static vars for each platform public static final boolean WINDOWS = (osType == OSType.OS_TYPE_WIN); public static final boolean SOLARIS = (osType == OSType.OS_TYPE_SOLARIS); public static final boolean MAC = (osType == OSType.OS_TYPE_MAC); public static final boolean FREEBSD = (osType == OSType.OS_TYPE_FREEBSD); public static final boolean LINUX = (osType == OSType.OS_TYPE_LINUX); public static final boolean OTHER = (osType == OSType.OS_TYPE_OTHER); public static final boolean PPC_64 = System.getProperties().getProperty("os.arch").contains("ppc64"); /** a Unix command to get the current user's groups list */ public static String[] getGroupsCommand() { return (WINDOWS) ? new String[] { "cmd", "/c", "groups" } : new String[] { "bash", "-c", "groups" }; } /** * a Unix command to get a given user's groups list. * If the OS is not WINDOWS, the command will get the user's primary group * first and finally get the groups list which includes the primary group. * i.e. the user's primary group will be included twice. */ public static String[] getGroupsForUserCommand(final String user) { //'groups username' command return is non-consistent across different unixes return (WINDOWS) ? new String[] { WINUTILS, "groups", "-F", "\"" + user + "\"" } : new String[] { "bash", "-c", "id -gn " + user + "&& id -Gn " + user }; } /** a Unix command to get a given netgroup's user list */ public static String[] getUsersForNetgroupCommand(final String netgroup) { //'groups username' command return is non-consistent across different unixes return (WINDOWS) ? new String[] { "cmd", "/c", "getent netgroup " + netgroup } : new String[] { "bash", "-c", "getent netgroup " + netgroup }; } /** Return a command to get permission information. */ public static String[] getGetPermissionCommand() { return (WINDOWS) ? new String[] { WINUTILS, "ls", "-F" } : new String[] { "/bin/ls", "-ld" }; } /** Return a command to set permission */ public static String[] getSetPermissionCommand(String perm, boolean recursive) { if (recursive) { return (WINDOWS) ? new String[] { WINUTILS, "chmod", "-R", perm } : new String[] { "chmod", "-R", perm }; } else { return (WINDOWS) ? new String[] { WINUTILS, "chmod", perm } : new String[] { "chmod", perm }; } } /** * Return a command to set permission for specific file. * * @param perm String permission to set * @param recursive boolean true to apply to all sub-directories recursively * @param file String file to set * @return String[] containing command and arguments */ public static String[] getSetPermissionCommand(String perm, boolean recursive, String file) { String[] baseCmd = getSetPermissionCommand(perm, recursive); String[] cmdWithFile = Arrays.copyOf(baseCmd, baseCmd.length + 1); cmdWithFile[cmdWithFile.length - 1] = file; return cmdWithFile; } /** Return a command to set owner */ public static String[] getSetOwnerCommand(String owner) { return (WINDOWS) ? new String[] { WINUTILS, "chown", "\"" + owner + "\"" } : new String[] { "chown", owner }; } /** Return a command to create symbolic links */ public static String[] getSymlinkCommand(String target, String link) { return WINDOWS ? new String[] { WINUTILS, "symlink", link, target } : new String[] { "ln", "-s", target, link }; } /** Return a command to read the target of the a symbolic link*/ public static String[] getReadlinkCommand(String link) { return WINDOWS ? new String[] { WINUTILS, "readlink", link } : new String[] { "readlink", link }; } /** Return a command for determining if process with specified pid is alive. */ public static String[] getCheckProcessIsAliveCommand(String pid) { return Shell.WINDOWS ? new String[] { Shell.WINUTILS, "task", "isAlive", pid } : new String[] { "kill", "-0", isSetsidAvailable ? "-" + pid : pid }; } /** Return a command to send a signal to a given pid */ public static String[] getSignalKillCommand(int code, String pid) { return Shell.WINDOWS ? new String[] { Shell.WINUTILS, "task", "kill", pid } : new String[] { "kill", "-" + code, isSetsidAvailable ? "-" + pid : pid }; } /** Return a regular expression string that match environment variables */ public static String getEnvironmentVariableRegex() { return (WINDOWS) ? "%([A-Za-z_][A-Za-z0-9_]*?)%" : "\\$([A-Za-z_][A-Za-z0-9_]*)"; } /** * Returns a File referencing a script with the given basename, inside the * given parent directory. The file extension is inferred by platform: ".cmd" * on Windows, or ".sh" otherwise. * * @param parent File parent directory * @param basename String script file basename * @return File referencing the script in the directory */ public static File appendScriptExtension(File parent, String basename) { return new File(parent, appendScriptExtension(basename)); } /** * Returns a script file name with the given basename. The file extension is * inferred by platform: ".cmd" on Windows, or ".sh" otherwise. * * @param basename String script file basename * @return String script file name */ public static String appendScriptExtension(String basename) { return basename + (WINDOWS ? ".cmd" : ".sh"); } /** * Returns a command to run the given script. The script interpreter is * inferred by platform: cmd on Windows or bash otherwise. * * @param script File script to run * @return String[] command to run the script */ public static String[] getRunScriptCommand(File script) { String absolutePath = script.getAbsolutePath(); return WINDOWS ? new String[] { "cmd", "/c", absolutePath } : new String[] { "/bin/bash", absolutePath }; } /** a Unix command to set permission */ public static final String SET_PERMISSION_COMMAND = "chmod"; /** a Unix command to set owner */ public static final String SET_OWNER_COMMAND = "chown"; /** a Unix command to set the change user's groups list */ public static final String SET_GROUP_COMMAND = "chgrp"; /** a Unix command to create a link */ public static final String LINK_COMMAND = "ln"; /** a Unix command to get a link target */ public static final String READ_LINK_COMMAND = "readlink"; /**Time after which the executing script would be timedout*/ protected long timeOutInterval = 0L; /** If or not script timed out*/ private AtomicBoolean timedOut; /** Centralized logic to discover and validate the sanity of the Hadoop * home directory. Returns either NULL or a directory that exists and * was specified via either -Dhadoop.home.dir or the HADOOP_HOME ENV * variable. This does a lot of work so it should only be called * privately for initialization once per process. **/ private static String checkHadoopHome() { // first check the Dflag hadoop.home.dir with JVM scope String home = System.getProperty("hadoop.home.dir"); // fall back to the system/user-global env variable if (home == null) { home = System.getenv("HADOOP_HOME"); } try { // couldn't find either setting for hadoop's home directory if (home == null) { throw new IOException("HADOOP_HOME or hadoop.home.dir are not set."); } if (home.startsWith("\"") && home.endsWith("\"")) { home = home.substring(1, home.length() - 1); } // check that the home setting is actually a directory that exists File homedir = new File(home); if (!homedir.isAbsolute() || !homedir.exists() || !homedir.isDirectory()) { throw new IOException("Hadoop home directory " + homedir + " does not exist, is not a directory, or is not an absolute path."); } home = homedir.getCanonicalPath(); } catch (IOException ioe) { if (LOG.isDebugEnabled()) { LOG.debug("Failed to detect a valid hadoop home directory", ioe); } home = null; } return home; } private static String HADOOP_HOME_DIR = checkHadoopHome(); // Public getter, throws an exception if HADOOP_HOME failed validation // checks and is being referenced downstream. public static final String getHadoopHome() throws IOException { if (HADOOP_HOME_DIR == null) { throw new IOException("Misconfigured HADOOP_HOME cannot be referenced."); } return HADOOP_HOME_DIR; } /** fully qualify the path to a binary that should be in a known hadoop * bin location. This is primarily useful for disambiguating call-outs * to executable sub-components of Hadoop to avoid clashes with other * executables that may be in the path. Caveat: this call doesn't * just format the path to the bin directory. It also checks for file * existence of the composed path. The output of this call should be * cached by callers. * */ public static final String getQualifiedBinPath(String executable) throws IOException { // construct hadoop bin path to the specified executable String fullExeName = HADOOP_HOME_DIR + File.separator + "bin" + File.separator + executable; File exeFile = new File(fullExeName); if (!exeFile.exists()) { throw new IOException("Could not locate executable " + fullExeName + " in the Hadoop binaries."); } return exeFile.getCanonicalPath(); } /** a Windows utility to emulate Unix commands */ public static final String WINUTILS = getWinUtilsPath(); public static final String getWinUtilsPath() { String winUtilsPath = null; try { if (WINDOWS) { winUtilsPath = getQualifiedBinPath("winutils.exe"); } } catch (IOException ioe) { LOG.error("Failed to locate the winutils binary in the hadoop binary path", ioe); } return winUtilsPath; } public static final boolean isSetsidAvailable = isSetsidSupported(); private static boolean isSetsidSupported() { if (Shell.WINDOWS) { return false; } ShellCommandExecutor shexec = null; boolean setsidSupported = true; try { String[] args = { "setsid", "bash", "-c", "echo $$" }; shexec = new ShellCommandExecutor(args); shexec.execute(); } catch (IOException ioe) { LOG.debug("setsid is not available on this machine. So not using it."); setsidSupported = false; } finally { // handle the exit code if (LOG.isDebugEnabled()) { LOG.debug("setsid exited with exit code " + (shexec != null ? shexec.getExitCode() : "(null executor)")); } } return setsidSupported; } /** Token separator regex used to parse Shell tool outputs */ public static final String TOKEN_SEPARATOR_REGEX = WINDOWS ? "[|\n\r]" : "[ \t\n\r\f]"; private long interval; // refresh interval in msec private long lastTime; // last time the command was performed final private boolean redirectErrorStream; // merge stdout and stderr private Map<String, String> environment; // env for the command execution private File dir; private Process process; // sub process used to execute the command private int exitCode; /**If or not script finished executing*/ private volatile AtomicBoolean completed; public Shell() { this(0L); } public Shell(long interval) { this(interval, false); } /** * @param interval the minimum duration to wait before re-executing the * command. */ public Shell(long interval, boolean redirectErrorStream) { this.interval = interval; this.lastTime = (interval < 0) ? 0 : -interval; this.redirectErrorStream = redirectErrorStream; } /** set the environment for the command * @param env Mapping of environment variables */ protected void setEnvironment(Map<String, String> env) { this.environment = env; } /** set the working directory * @param dir The directory where the command would be executed */ protected void setWorkingDirectory(File dir) { this.dir = dir; } /** check to see if a command needs to be executed and execute if needed */ protected void run() throws IOException { if (lastTime + interval > Time.monotonicNow()) return; exitCode = 0; // reset for next run runCommand(); } /** Run a command */ private void runCommand() throws IOException { ProcessBuilder builder = new ProcessBuilder(getExecString()); Timer timeOutTimer = null; ShellTimeoutTimerTask timeoutTimerTask = null; timedOut = new AtomicBoolean(false); completed = new AtomicBoolean(false); if (environment != null) { builder.environment().putAll(this.environment); } if (dir != null) { builder.directory(this.dir); } builder.redirectErrorStream(redirectErrorStream); if (Shell.WINDOWS) { synchronized (WindowsProcessLaunchLock) { // To workaround the race condition issue with child processes // inheriting unintended handles during process launch that can // lead to hangs on reading output and error streams, we // serialize process creation. More info available at: // http://support.microsoft.com/kb/315939 process = builder.start(); } } else { process = builder.start(); } if (timeOutInterval > 0) { timeOutTimer = new Timer("Shell command timeout"); timeoutTimerTask = new ShellTimeoutTimerTask(this); //One time scheduling. timeOutTimer.schedule(timeoutTimerTask, timeOutInterval); } final BufferedReader errReader = new BufferedReader( new InputStreamReader(process.getErrorStream(), Charset.defaultCharset())); BufferedReader inReader = new BufferedReader( new InputStreamReader(process.getInputStream(), Charset.defaultCharset())); final StringBuffer errMsg = new StringBuffer(); // read error and input streams as this would free up the buffers // free the error stream buffer Thread errThread = new Thread() { @Override public void run() { try { String line = errReader.readLine(); while ((line != null) && !isInterrupted()) { errMsg.append(line); errMsg.append(System.getProperty("line.separator")); line = errReader.readLine(); } } catch (IOException ioe) { LOG.warn("Error reading the error stream", ioe); } } }; try { errThread.start(); } catch (IllegalStateException ise) { } catch (OutOfMemoryError oe) { LOG.error("Caught " + oe + ". One possible reason is that ulimit" + " setting of 'max user processes' is too low. If so, do" + " 'ulimit -u <largerNum>' and try again."); throw oe; } try { parseExecResult(inReader); // parse the output // clear the input stream buffer String line = inReader.readLine(); while (line != null) { line = inReader.readLine(); } // wait for the process to finish and check the exit code exitCode = process.waitFor(); // make sure that the error thread exits joinThread(errThread); completed.set(true); //the timeout thread handling //taken care in finally block if (exitCode != 0) { throw new ExitCodeException(exitCode, errMsg.toString()); } } catch (InterruptedException ie) { throw new IOException(ie.toString()); } finally { if (timeOutTimer != null) { timeOutTimer.cancel(); } // close the input stream try { // JDK 7 tries to automatically drain the input streams for us // when the process exits, but since close is not synchronized, // it creates a race if we close the stream first and the same // fd is recycled. the stream draining thread will attempt to // drain that fd!! it may block, OOM, or cause bizarre behavior // see: https://bugs.openjdk.java.net/browse/JDK-8024521 // issue is fixed in build 7u60 InputStream stdout = process.getInputStream(); synchronized (stdout) { inReader.close(); } } catch (IOException ioe) { LOG.warn("Error while closing the input stream", ioe); } if (!completed.get()) { errThread.interrupt(); joinThread(errThread); } try { InputStream stderr = process.getErrorStream(); synchronized (stderr) { errReader.close(); } } catch (IOException ioe) { LOG.warn("Error while closing the error stream", ioe); } process.destroy(); lastTime = Time.monotonicNow(); } } private static void joinThread(Thread t) { while (t.isAlive()) { try { t.join(); } catch (InterruptedException ie) { if (LOG.isWarnEnabled()) { LOG.warn("Interrupted while joining on: " + t, ie); } t.interrupt(); // propagate interrupt } } } /** return an array containing the command name & its parameters */ protected abstract String[] getExecString(); /** Parse the execution result */ protected abstract void parseExecResult(BufferedReader lines) throws IOException; /** * Get the environment variable */ public String getEnvironment(String env) { return environment.get(env); } /** get the current sub-process executing the given command * @return process executing the command */ public Process getProcess() { return process; } /** get the exit code * @return the exit code of the process */ public int getExitCode() { return exitCode; } /** * This is an IOException with exit code added. */ public static class ExitCodeException extends IOException { private final int exitCode; public ExitCodeException(int exitCode, String message) { super(message); this.exitCode = exitCode; } public int getExitCode() { return exitCode; } @Override public String toString() { final StringBuilder sb = new StringBuilder("ExitCodeException "); sb.append("exitCode=").append(exitCode).append(": "); sb.append(super.getMessage()); return sb.toString(); } } public interface CommandExecutor { void execute() throws IOException; int getExitCode() throws IOException; String getOutput() throws IOException; void close(); } /** * A simple shell command executor. * * <code>ShellCommandExecutor</code>should be used in cases where the output * of the command needs no explicit parsing and where the command, working * directory and the environment remains unchanged. The output of the command * is stored as-is and is expected to be small. */ public static class ShellCommandExecutor extends Shell implements CommandExecutor { private String[] command; private StringBuffer output; public ShellCommandExecutor(String[] execString) { this(execString, null); } public ShellCommandExecutor(String[] execString, File dir) { this(execString, dir, null); } public ShellCommandExecutor(String[] execString, File dir, Map<String, String> env) { this(execString, dir, env, 0L); } /** * Create a new instance of the ShellCommandExecutor to execute a command. * * @param execString The command to execute with arguments * @param dir If not-null, specifies the directory which should be set * as the current working directory for the command. * If null, the current working directory is not modified. * @param env If not-null, environment of the command will include the * key-value pairs specified in the map. If null, the current * environment is not modified. * @param timeout Specifies the time in milliseconds, after which the * command will be killed and the status marked as timedout. * If 0, the command will not be timed out. */ public ShellCommandExecutor(String[] execString, File dir, Map<String, String> env, long timeout) { command = execString.clone(); if (dir != null) { setWorkingDirectory(dir); } if (env != null) { setEnvironment(env); } timeOutInterval = timeout; } /** Execute the shell command. */ public void execute() throws IOException { this.run(); } @Override public String[] getExecString() { return command; } @Override protected void parseExecResult(BufferedReader lines) throws IOException { output = new StringBuffer(); char[] buf = new char[512]; int nRead; while ((nRead = lines.read(buf, 0, buf.length)) > 0) { output.append(buf, 0, nRead); } } /** Get the output of the shell command.*/ public String getOutput() { return (output == null) ? "" : output.toString(); } /** * Returns the commands of this instance. * Arguments with spaces in are presented with quotes round; other * arguments are presented raw * * @return a string representation of the object. */ @Override public String toString() { StringBuilder builder = new StringBuilder(); String[] args = getExecString(); for (String s : args) { if (s.indexOf(' ') >= 0) { builder.append('"').append(s).append('"'); } else { builder.append(s); } builder.append(' '); } return builder.toString(); } @Override public void close() { } } /** * To check if the passed script to shell command executor timed out or * not. * * @return if the script timed out. */ public boolean isTimedOut() { return timedOut.get(); } /** * Set if the command has timed out. * */ private void setTimedOut() { this.timedOut.set(true); } /** * Static method to execute a shell command. * Covers most of the simple cases without requiring the user to implement * the <code>Shell</code> interface. * @param cmd shell command to execute. * @return the output of the executed command. */ public static String execCommand(String... cmd) throws IOException { return execCommand(null, cmd, 0L); } /** * Static method to execute a shell command. * Covers most of the simple cases without requiring the user to implement * the <code>Shell</code> interface. * @param env the map of environment key=value * @param cmd shell command to execute. * @param timeout time in milliseconds after which script should be marked timeout * @return the output of the executed command.o */ public static String execCommand(Map<String, String> env, String[] cmd, long timeout) throws IOException { ShellCommandExecutor exec = new ShellCommandExecutor(cmd, null, env, timeout); exec.execute(); return exec.getOutput(); } /** * Static method to execute a shell command. * Covers most of the simple cases without requiring the user to implement * the <code>Shell</code> interface. * @param env the map of environment key=value * @param cmd shell command to execute. * @return the output of the executed command. */ public static String execCommand(Map<String, String> env, String... cmd) throws IOException { return execCommand(env, cmd, 0L); } /** * Timer which is used to timeout scripts spawned off by shell. */ private static class ShellTimeoutTimerTask extends TimerTask { private Shell shell; public ShellTimeoutTimerTask(Shell shell) { this.shell = shell; } @Override public void run() { Process p = shell.getProcess(); try { p.exitValue(); } catch (Exception e) { //Process has not terminated. //So check if it has completed //if not just destroy it. if (p != null && !shell.completed.get()) { shell.setTimedOut(); p.destroy(); } } } } }