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.distributedlog.lock;
  
  import java.io.IOException;
  import java.util.concurrent.CancellationException;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicReference;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.bookkeeper.common.util.OrderedScheduler;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.distributedlog.ZooKeeperClient;
  import org.apache.distributedlog.exceptions.DLInterruptedException;
  
  /**
   * Factory to create zookeeper based locks.
   */
  public class ZKSessionLockFactory implements SessionLockFactory {
  
      private final ZooKeeperClient zkc;
      private final String clientId;
      private final OrderedScheduler lockStateExecutor;
      private final long lockOpTimeout;
      private final int lockCreationRetries;
      private final long zkRetryBackoffMs;
  
      // Stats
      private final StatsLogger lockStatsLogger;
  
      public ZKSessionLockFactory(ZooKeeperClient zkc,
                                  String clientId,
                                  OrderedScheduler lockStateExecutor,
                                  int lockCreationRetries,
                                  long lockOpTimeout,
                                  long zkRetryBackoffMs,
                                  StatsLogger statsLogger) {
          this.zkc = zkc;
          this.clientId = clientId;
          this.lockStateExecutor = lockStateExecutor;
          this.lockCreationRetries = lockCreationRetries;
          this.lockOpTimeout = lockOpTimeout;
          this.zkRetryBackoffMs = zkRetryBackoffMs;
  
          this.lockStatsLogger = statsLogger.scope("lock");
      }
  
      @Override
      public CompletableFuture<SessionLock> createLock(String lockPath,
                                                       DistributedLockContext context) {
          AtomicInteger numRetries = new AtomicInteger(lockCreationRetries);
          final AtomicReference<Throwable> interruptedException = new AtomicReference<Throwable>(null);
          CompletableFuture<SessionLock> createPromise = FutureUtils.createFuture();
          createPromise.whenComplete((value, cause) -> {
              if (null != cause && cause instanceof CancellationException) {
                  interruptedException.set(cause);
              }
          });
          createLock(
                  lockPath,
                  context,
                  interruptedException,
                  numRetries,
                  createPromise,
                  0L);
          return createPromise;
      }
  
      void createLock(final String lockPath,
                      final DistributedLockContext context,
                      final AtomicReference<Throwable> interruptedException,
                      final AtomicInteger numRetries,
                      final CompletableFuture<SessionLock> createPromise,
                      final long delayMs) {
          lockStateExecutor.scheduleOrdered(lockPath, () -> {
              if (null != interruptedException.get()) {
                  createPromise.completeExceptionally(interruptedException.get());
                  return;
              }
              try {
                  SessionLock lock = new ZKSessionLock(
                          zkc,
                          lockPath,
                          clientId,
                          lockStateExecutor,
                          lockOpTimeout,
                          lockStatsLogger,
                          context);
                  createPromise.complete(lock);
              } catch (DLInterruptedException dlie) {
                  // if the creation is interrupted, throw the exception without retrie.
                  createPromise.completeExceptionally(dlie);
                  return;
              } catch (IOException e) {
                  if (numRetries.getAndDecrement() < 0) {
                      createPromise.completeExceptionally(e);
                      return;
                  }
                  createLock(
                          lockPath,
                          context,
                          interruptedException,
                          numRetries,
                          createPromise,
                          zkRetryBackoffMs);
              }
          }, delayMs, TimeUnit.MILLISECONDS);
      }
  }
  