content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.multi.process;
  
  import alluxio.conf.PropertyKey;
  import alluxio.util.io.PathUtils;
  
  import com.google.common.base.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Map;
  import java.util.Map.Entry;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Class for launching another class in a new processes.
   */
  @ThreadSafe
  public final class ExternalProcess {
    private static final Logger LOG = LoggerFactory.getLogger(ExternalProcess.class);
    private final Map<PropertyKey, Object> mConf;
    private final Class<?> mClazz;
    private final File mOutFile;
  
    private Process mProcess;
  
    /**
     * @param conf alluxio configuration properties for the process
     * @param clazz the class to run
     * @param outfile the file to write process output to
     */
    public ExternalProcess(Map<PropertyKey, Object> conf, Class<?> clazz, File outfile) {
      mConf = conf;
      mClazz = clazz;
      mOutFile = outfile;
    }
  
    /**
     * Starts the process.
     */
    public synchronized void start() throws IOException {
      Preconditions.checkState(mProcess == null, "Process is already running");
      String java = PathUtils.concatPath(System.getProperty("java.home"), "bin", "java");
      String classpath = System.getProperty("java.class.path");
      List<String> args = new ArrayList<>(Arrays.asList(java, "-cp", classpath));
      for (Entry<PropertyKey, Object> entry : mConf.entrySet()) {
        args.add(String.format("-D%s=%s", entry.getKey().toString(), entry.getValue()));
      }
      args.add(mClazz.getCanonicalName());
      ProcessBuilder pb = new ProcessBuilder(args);
      pb.redirectError(mOutFile);
      pb.redirectOutput(mOutFile);
      mProcess = pb.start();
    }
  
    /**
     * Stops the process.
     */
    public synchronized void stop() {
      if (mProcess != null) {
        try {
          mProcess.destroyForcibly().waitFor();
        } catch (InterruptedException e) {
          LOG.warn("Interrupted while waiting for process to close", e);
        }
        mProcess = null;
      }
    }
  }
  