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.master;
  
  import alluxio.conf.Configuration;
  import alluxio.conf.PropertyKey;
  import alluxio.grpc.NodeState;
  import alluxio.master.journal.ufs.UfsJournalMultiMasterPrimarySelector;
  import alluxio.util.interfaces.Scoped;
  
  import java.net.InetSocketAddress;
  import java.util.function.Consumer;
  
  /**
   * Interface for a class which can determine whether the local master is the primary.
   */
  public interface PrimarySelector {
    /**
     * Factory for creating primary selectors.
     */
    final class Factory {
      /**
       * @return a primary selector based on zookeeper configuration
       */
      public static PrimarySelector createZkPrimarySelector() {
        String zkAddress = Configuration.getString(PropertyKey.ZOOKEEPER_ADDRESS);
        String zkElectionPath = Configuration.getString(PropertyKey.ZOOKEEPER_ELECTION_PATH);
        String zkLeaderPath = Configuration.getString(PropertyKey.ZOOKEEPER_LEADER_PATH);
        return new UfsJournalMultiMasterPrimarySelector(zkAddress, zkElectionPath, zkLeaderPath);
      }
  
      /**
       * @return a job master primary selector based on zookeeper configuration
       */
      public static PrimarySelector createZkJobPrimarySelector() {
        String zkAddress = Configuration.getString(PropertyKey.ZOOKEEPER_ADDRESS);
        String zkElectionPath = Configuration.getString(
            PropertyKey.ZOOKEEPER_JOB_ELECTION_PATH);
        String zkLeaderPath = Configuration.getString(PropertyKey.ZOOKEEPER_JOB_LEADER_PATH);
        return new UfsJournalMultiMasterPrimarySelector(zkAddress, zkElectionPath, zkLeaderPath);
      }
  
      private Factory() {} // Not intended for instantiation.
    }
  
    /**
     * Starts the primary selector.
     *
     * @param localAddress the address of the local master
     */
    void start(InetSocketAddress localAddress);
  
    /**
     * Stops the primary selector.
     */
    void stop();
  
    /**
     * @return the current state
     */
    NodeState getState();
  
    /**
     * @return the current state without the lock acquired
     */
    NodeState getStateUnsafe();
  
    /**
     * Registers a listener to be executed whenever the selector's state updates.
     *
     * The listener will be executed synchronously in the state update thread, so it should run
     * quickly.
     *
     * @param listener the listener
     * @return an object which will unregister the listener when closed
     */
    Scoped onStateChange(Consumer<NodeState> listener);
  
    /**
     * Blocks until the primary selector enters the specified state.
     *
     * @param state the state to wait for
     */
    void waitForState(NodeState state) throws InterruptedException;
  }
  