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 com.google.common.base.Preconditions;
  import com.google.common.collect.ImmutableMap;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.Closeable;
  import java.io.File;
  import java.io.IOException;
  import java.util.Map;
  import javax.annotation.Nullable;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Class for running and interacting with an Alluxio master in a separate process.
   */
  @ThreadSafe
  public abstract class BaseMaster implements Closeable {
    private static final Logger LOG = LoggerFactory.getLogger(BaseMaster.class);
  
    private final File mLogsDir;
    final Map<PropertyKey, Object> mProperties;
  
    private ExternalProcess mProcess;
  
    /**
     * @param logsDir logs directory
     * @param properties alluxio properties
     */
    public BaseMaster(File logsDir, Map<PropertyKey, Object> properties) throws IOException {
      mLogsDir = logsDir;
      mProperties = properties;
    }
  
    /**
     * Updates the master's configuration. This update will take effect the next time the master
     * is started.
     *
     * @param key the conf key to update
     * @param value the value to set, or null to unset the key
     */
    public void updateConf(PropertyKey key, @Nullable Object value) {
      if (value == null) {
        mProperties.remove(key);
      } else {
        mProperties.put(key, value);
      }
    }
  
    abstract int getPort();
  
    abstract Class<?> getProcessClass();
  
    /**
     * Launches the master process.
     */
    public synchronized void start() {
      Preconditions.checkState(mProcess == null, "Master is already running");
      LOG.info("Starting master type {} with port {}", getProcessClass(), getPort());
      mProcess = new ExternalProcess(mProperties, getProcessClass(),
          new File(mLogsDir, "master.out"));
      try {
        mProcess.start();
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
  
    /**
     * @return the configuration used by this master
     */
    public Map<PropertyKey, Object> getConf() {
      return ImmutableMap.copyOf(mProperties);
    }
  
    @Override
    public synchronized void close() {
      if (mProcess != null) {
        mProcess.stop();
        mProcess = null;
      }
    }
  }
  