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.bookkeeper.replication;
  
  import static org.apache.bookkeeper.replication.ReplicationStats.AUDITOR_SCOPE;
  
  import com.google.common.annotations.VisibleForTesting;
  import java.io.IOException;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.RejectedExecutionException;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.atomic.AtomicBoolean;
  import org.apache.bookkeeper.client.BKException;
  import org.apache.bookkeeper.client.BookKeeper;
  import org.apache.bookkeeper.conf.ServerConfiguration;
  import org.apache.bookkeeper.meta.LedgerAuditorManager;
  import org.apache.bookkeeper.net.BookieId;
  import org.apache.bookkeeper.replication.ReplicationException.UnavailableException;
  import org.apache.bookkeeper.stats.NullStatsLogger;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.bookkeeper.stats.annotations.StatsDoc;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Performing auditor election using Apache ZooKeeper. Using ZooKeeper as a
   * coordination service, when a bookie bids for auditor, it creates an ephemeral
   * sequential file (znode) on ZooKeeper and considered as their vote. Vote
   * format is 'V_sequencenumber'. Election will be done by comparing the
   * ephemeral sequential numbers and the bookie which has created the least znode
   * will be elected as Auditor. All the other bookies will be watching on their
   * predecessor znode according to the ephemeral sequence numbers.
   */
  @StatsDoc(
      name = AUDITOR_SCOPE,
      help = "Auditor related stats"
  )
  public class AuditorElector {
      private static final Logger LOG = LoggerFactory
              .getLogger(AuditorElector.class);
  
      private final String bookieId;
      private final ServerConfiguration conf;
      private final BookKeeper bkc;
      private final boolean ownBkc;
      private final ExecutorService executor;
      private final LedgerAuditorManager ledgerAuditorManager;
  
      Auditor auditor;
      private AtomicBoolean running = new AtomicBoolean(false);
  
  
      private final StatsLogger statsLogger;
  
  
      @VisibleForTesting
      public AuditorElector(final String bookieId, ServerConfiguration conf) throws UnavailableException {
          this(
              bookieId,
              conf,
              Auditor.createBookKeeperClientThrowUnavailableException(conf),
              true);
      }
  
      /**
       * AuditorElector for performing the auditor election.
       *
       * @param bookieId
       *            - bookie identifier, comprises HostAddress:Port
       * @param conf
       *            - configuration
       * @param bkc
       *            - bookkeeper instance
       * @throws UnavailableException
       *             throws unavailable exception while initializing the elector
       */
      public AuditorElector(final String bookieId,
                            ServerConfiguration conf,
                            BookKeeper bkc,
                            boolean ownBkc) throws UnavailableException {
          this(bookieId, conf, bkc, NullStatsLogger.INSTANCE, ownBkc);
      }
  
      /**
       * AuditorElector for performing the auditor election.
       *
       * @param bookieId
       *            - bookie identifier, comprises HostAddress:Port
       * @param conf
       *            - configuration
       * @param bkc
       *            - bookkeeper instance
       * @param statsLogger
       *            - stats logger
       * @throws UnavailableException
       *             throws unavailable exception while initializing the elector
       */
      public AuditorElector(final String bookieId,
                            ServerConfiguration conf,
                            BookKeeper bkc,
                            StatsLogger statsLogger,
                            boolean ownBkc) throws UnavailableException {
          this.bookieId = bookieId;
          this.conf = conf;
          this.bkc = bkc;
          this.ownBkc = ownBkc;
          this.statsLogger = statsLogger;
          try {
              this.ledgerAuditorManager = bkc.getLedgerManagerFactory().newLedgerAuditorManager();
          } catch (Exception e) {
              throw new UnavailableException("Failed to instantiate the ledger auditor manager", e);
          }
          executor = Executors.newSingleThreadExecutor(new ThreadFactory() {
                  @Override
                  public Thread newThread(Runnable r) {
                      return new Thread(r, "AuditorElector-" + bookieId);
                  }
              });
      }
  
      public Future<?> start() {
          running.set(true);
          return submitElectionTask();
      }
  
      /**
       * Run cleanup operations for the auditor elector.
       */
      private Future<?> submitShutdownTask() {
          return executor.submit(shutdownTask);
      }
  
      Runnable shutdownTask = new Runnable() {
          @Override
          public void run() {
              if (!running.compareAndSet(true, false)) {
                  return;
              }
  
              try {
                  ledgerAuditorManager.close();
              } catch (InterruptedException ie) {
                  Thread.currentThread().interrupt();
                  LOG.warn("InterruptedException while closing ledger auditor manager", ie);
              } catch (Exception ke) {
                  LOG.error("Exception while closing ledger auditor manager", ke);
              }
          }
      };
  
      /**
       * Performing the auditor election using the ZooKeeper ephemeral sequential
       * znode. The bookie which has created the least sequential will be elect as
       * Auditor.
       */
      @VisibleForTesting
      Future<?> submitElectionTask() {
  
          Runnable r = new Runnable() {
                  @Override
                  public void run() {
                      if (!running.get()) {
                          return;
                      }
                      try {
                          ledgerAuditorManager.tryToBecomeAuditor(bookieId, e -> handleAuditorEvent(e));
  
                          auditor = new Auditor(bookieId, conf, bkc, false, statsLogger);
                          auditor.start();
                      } catch (InterruptedException e) {
                          LOG.error("Interrupted while performing auditor election", e);
                          Thread.currentThread().interrupt();
                          submitShutdownTask();
                      } catch (Exception e) {
                          LOG.error("Exception while performing auditor election", e);
                          submitShutdownTask();
                      }
                  }
              };
          try {
              return executor.submit(r);
          } catch (RejectedExecutionException e) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("Executor was already closed");
              }
              return CompletableFuture.completedFuture(null);
          }
      }
  
      private void handleAuditorEvent(LedgerAuditorManager.AuditorEvent e) {
          switch (e) {
              case SessionLost:
                  LOG.error("Lost ZK connection, shutting down");
                  submitShutdownTask();
                  break;
  
              case VoteWasDeleted:
                  submitElectionTask();
                  break;
          }
      }
  
      @VisibleForTesting
      Auditor getAuditor() {
          return auditor;
      }
  
  
      public BookieId getCurrentAuditor() throws IOException, InterruptedException {
          return ledgerAuditorManager.getCurrentAuditor();
      }
  
      /**
       * Shutting down AuditorElector.
       */
      public void shutdown() throws InterruptedException {
          synchronized (this) {
              if (executor.isShutdown()) {
                  return;
              }
              // close auditor manager
              try {
                  submitShutdownTask().get(10, TimeUnit.SECONDS);
                  executor.shutdown();
              } catch (ExecutionException e) {
                  LOG.warn("Failed to close auditor manager", e);
                  executor.shutdownNow();
                  shutdownTask.run();
              } catch (TimeoutException e) {
                  LOG.warn("Failed to close auditor manager in 10 seconds", e);
                  executor.shutdownNow();
                  shutdownTask.run();
              }
          }
  
          if (auditor != null) {
              auditor.shutdown();
              auditor = null;
          }
          if (ownBkc) {
              try {
                  bkc.close();
              } catch (BKException e) {
                  LOG.warn("Failed to close bookkeeper client", e);
              }
          }
      }
  
      /**
       * If current bookie is running as auditor, return the status of the
       * auditor. Otherwise return the status of elector.
       *
       * @return
       */
      public boolean isRunning() {
          if (auditor != null) {
              return auditor.isRunning();
          }
          return running.get();
      }
  
      @Override
      public String toString() {
          return "AuditorElector for " + bookieId;
      }
  }
  