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.spark.launcher;
  
  import java.io.BufferedReader;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.concurrent.ThreadFactory;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  /**
   * Redirects lines read from a given input stream to a j.u.l.Logger (at INFO level).
   */
  class OutputRedirector {
  
    private final BufferedReader reader;
    private final Logger sink;
    private final Thread thread;
  
    private volatile boolean active;
  
    OutputRedirector(InputStream in, ThreadFactory tf) {
      this(in, OutputRedirector.class.getName(), tf);
    }
  
    OutputRedirector(InputStream in, String loggerName, ThreadFactory tf) {
      this.active = true;
      this.reader = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8));
      this.thread = tf.newThread(new Runnable() {
        @Override
        public void run() {
          redirect();
        }
      });
      this.sink = Logger.getLogger(loggerName);
      thread.start();
    }
  
    private void redirect() {
      try {
        String line;
        while ((line = reader.readLine()) != null) {
          if (active) {
            sink.info(line.replaceFirst("\\s*$", ""));
          }
        }
      } catch (IOException e) {
        sink.log(Level.FINE, "Error reading child process output.", e);
      }
    }
  
    /**
     * This method just stops the output of the process from showing up in the local logs.
     * The child's output will still be read (and, thus, the redirect thread will still be
     * alive) to avoid the child process hanging because of lack of output buffer.
     */
    void stop() {
      active = false;
    }
  
  }
  