content: /*
   * 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.kafka.common.utils;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.nio.charset.StandardCharsets;
  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>.
   */
  public abstract class Shell {
  
      private static final Logger LOG = LoggerFactory.getLogger(Shell.class);
  
      /** Return an array containing the command name and its parameters */
      protected abstract String[] execString();
  
      /** Parse the execution result */
      protected abstract void parseExecResult(BufferedReader lines) throws IOException;
  
      private final long timeout;
  
      private int exitCode;
      private Process process; // sub process used to execute the command
  
      /* If or not script finished executing */
      private volatile AtomicBoolean completed;
  
      /**
       * @param timeout Specifies the time in milliseconds, after which the command will be killed. -1 means no timeout.
       */
      public Shell(long timeout) {
          this.timeout = timeout;
      }
  
      /** get the exit code
       * @return the exit code of the process
       */
      public int exitCode() {
          return exitCode;
      }
  
      /** get the current sub-process executing the given command
       * @return process executing the command
       */
      public Process process() {
          return process;
      }
  
      protected void run() throws IOException {
          exitCode = 0; // reset for next run
          runCommand();
      }
  
      /** Run a command */
      private void runCommand() throws IOException {
          ProcessBuilder builder = new ProcessBuilder(execString());
          Timer timeoutTimer = null;
          completed = new AtomicBoolean(false);
  
          process = builder.start();
          if (timeout > -1) {
              timeoutTimer = new Timer();
              //One time scheduling.
              timeoutTimer.schedule(new ShellTimeoutTimerTask(this), timeout);
          }
          final BufferedReader errReader = new BufferedReader(
              new InputStreamReader(process.getErrorStream(), StandardCharsets.UTF_8));
          BufferedReader inReader = new BufferedReader(
              new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8));
          final StringBuffer errMsg = new StringBuffer();
  
          // read error and input streams as this would free up the buffers
          // free the error stream buffer
          Thread errThread = KafkaThread.nonDaemon("kafka-shell-thread", () -> {
              try {
                  String line = errReader.readLine();
                  while ((line != null) && !Thread.currentThread().isInterrupted()) {
                      errMsg.append(line);
                      errMsg.append(System.lineSeparator());
                      line = errReader.readLine();
                  }
              } catch (IOException ioe) {
                  LOG.warn("Error reading the error stream", ioe);
              }
          });
          errThread.start();
  
          try {
              parseExecResult(inReader); // parse the output
              // wait for the process to finish and check the exit code
              exitCode = process.waitFor();
              try {
                  // make sure that the error thread exits
                  errThread.join();
              } catch (InterruptedException ie) {
                  LOG.warn("Interrupted while reading the error stream", ie);
              }
              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 {
                  inReader.close();
              } catch (IOException ioe) {
                  LOG.warn("Error while closing the input stream", ioe);
              }
              if (!completed.get())
                  errThread.interrupt();
  
              try {
                  errReader.close();
              } catch (IOException ioe) {
                  LOG.warn("Error while closing the error stream", ioe);
              }
  
              process.destroy();
          }
      }
  
  
      /**
       * This is an IOException with exit code added.
       */
      public static class ExitCodeException extends IOException {
          int exitCode;
  
          public ExitCodeException(int exitCode, String message) {
              super(message);
              this.exitCode = exitCode;
          }
  
          public int getExitCode() {
              return exitCode;
          }
      }
  
      /**
       * 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 {
  
          private final String[] command;
          private StringBuffer output;
  
          /**
           * Create a new instance of the ShellCommandExecutor to execute a command.
           *
           * @param execString The command to execute with arguments
           * @param timeout Specifies the time in milliseconds, after which the
           *                command will be killed. -1 means no timeout.
           */
  
          public ShellCommandExecutor(String[] execString, long timeout) {
              super(timeout);
              command = execString.clone();
          }
  
  
          /** Execute the shell command. */
          public void execute() throws IOException {
              this.run();
          }
  
          protected String[] execString() {
              return command;
          }
  
          protected void parseExecResult(BufferedReader reader) throws IOException {
              output = new StringBuffer();
              char[] buf = new char[512];
              int nRead;
              while ((nRead = reader.read(buf, 0, buf.length)) > 0) {
                  output.append(buf, 0, nRead);
              }
          }
  
          /** Get the output of the shell command.*/
          public String output() {
              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.
           */
          public String toString() {
              StringBuilder builder = new StringBuilder();
              String[] args = execString();
              for (String s : args) {
                  if (s.indexOf(' ') >= 0) {
                      builder.append('"').append(s).append('"');
                  } else {
                      builder.append(s);
                  }
                  builder.append(' ');
              }
              return builder.toString();
          }
      }
  
      /**
       * 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(cmd, -1);
      }
  
      /**
       * 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.
       * @param timeout time in milliseconds after which script should be killed. -1 means no timeout.
       * @return the output of the executed command.
       */
      public static String execCommand(String[] cmd, long timeout) throws IOException {
          ShellCommandExecutor exec = new ShellCommandExecutor(cmd, timeout);
          exec.execute();
          return exec.output();
      }
  
      /**
       * Timer which is used to timeout scripts spawned off by shell.
       */
      private static class ShellTimeoutTimerTask extends TimerTask {
  
          private final Shell shell;
  
          public ShellTimeoutTimerTask(Shell shell) {
              this.shell = shell;
          }
  
          @Override
          public void run() {
              Process p = shell.process();
              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()) {
                      p.destroy();
                  }
              }
          }
      }
  
  }
  