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.zookeeper;
  
  import com.google.common.util.concurrent.RateLimiter;
  import java.util.concurrent.Callable;
  import java.util.concurrent.TimeUnit;
  import org.apache.bookkeeper.common.util.MathUtils;
  import org.apache.bookkeeper.stats.OpStatsLogger;
  import org.apache.zookeeper.KeeperException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Provide a mechanism to perform an operation on ZooKeeper that is safe on disconnections
   * and recoverable errors.
   */
  class ZooWorker {
  
      private static final Logger logger = LoggerFactory.getLogger(ZooWorker.class);
  
      int attempts = 0;
      long startTimeNanos;
      long elapsedTimeMs = 0L;
      final RetryPolicy retryPolicy;
      final OpStatsLogger statsLogger;
  
      ZooWorker(RetryPolicy retryPolicy, OpStatsLogger statsLogger) {
          this.retryPolicy = retryPolicy;
          this.statsLogger = statsLogger;
          this.startTimeNanos = MathUtils.nowInNano();
      }
  
      public boolean allowRetry(int rc) {
          elapsedTimeMs = MathUtils.elapsedMSec(startTimeNanos);
          if (!ZooWorker.isRecoverableException(rc)) {
              if (KeeperException.Code.OK.intValue() == rc) {
                  statsLogger.registerSuccessfulEvent(MathUtils.elapsedMicroSec(startTimeNanos), TimeUnit.MICROSECONDS);
              } else {
                  statsLogger.registerFailedEvent(MathUtils.elapsedMicroSec(startTimeNanos), TimeUnit.MICROSECONDS);
              }
              return false;
          }
          ++attempts;
          return retryPolicy.allowRetry(attempts, elapsedTimeMs);
      }
  
      public long nextRetryWaitTime() {
          return retryPolicy.nextRetryWaitTime(attempts, elapsedTimeMs);
      }
  
      /**
       * Check whether the given result code is recoverable by retry.
       *
       * @param rc result code
       * @return true if given result code is recoverable.
       */
      public static boolean isRecoverableException(int rc) {
          return KeeperException.Code.CONNECTIONLOSS.intValue() == rc
              || KeeperException.Code.OPERATIONTIMEOUT.intValue() == rc
              || KeeperException.Code.SESSIONMOVED.intValue() == rc
              || KeeperException.Code.SESSIONEXPIRED.intValue() == rc;
      }
  
      /**
       * Check whether the given exception is recoverable by retry.
       *
       * @param exception given exception
       * @return true if given exception is recoverable.
       */
      public static boolean isRecoverableException(KeeperException exception) {
          return isRecoverableException(exception.code().intValue());
      }
  
      interface ZooCallable<T> {
          /**
           * Be compatible with ZooKeeper interface.
           *
           * @return value
           * @throws InterruptedException
           * @throws KeeperException
           */
          T call() throws InterruptedException, KeeperException;
      }
  
      /**
       * Execute a sync zookeeper operation with a given retry policy.
       *
       * @param client
       *          ZooKeeper client.
       * @param proc
       *          Synchronous zookeeper operation wrapped in a {@link Callable}.
       * @param retryPolicy
       *          Retry policy to execute the synchronous operation.
       * @param rateLimiter
       *          Rate limiter for zookeeper calls
       * @param statsLogger
       *          Stats Logger for zookeeper client.
       * @return result of the zookeeper operation
       * @throws KeeperException any non-recoverable exception or recoverable exception exhausted all retires.
       * @throws InterruptedException the operation is interrupted.
       */
      public static<T> T syncCallWithRetries(ZooKeeperClient client,
                                             ZooCallable<T> proc,
                                             RetryPolicy retryPolicy,
                                             RateLimiter rateLimiter,
                                             OpStatsLogger statsLogger)
      throws KeeperException, InterruptedException {
          T result = null;
          boolean isDone = false;
          int attempts = 0;
          long startTimeNanos = MathUtils.nowInNano();
          while (!isDone) {
              try {
                  if (null != client) {
                      client.waitForConnection();
                  }
                  logger.debug("Execute {} at {} retry attempt.", proc, attempts);
                  if (null != rateLimiter) {
                      rateLimiter.acquire();
                  }
                  result = proc.call();
                  isDone = true;
                  statsLogger.registerSuccessfulEvent(MathUtils.elapsedMicroSec(startTimeNanos), TimeUnit.MICROSECONDS);
              } catch (KeeperException e) {
                  ++attempts;
                  boolean rethrow = true;
                  long elapsedTime = MathUtils.elapsedMSec(startTimeNanos);
                  if (((null != client && isRecoverableException(e)) || null == client)
                      && retryPolicy.allowRetry(attempts, elapsedTime)) {
                      rethrow = false;
                  }
                  if (rethrow) {
                      statsLogger.registerFailedEvent(MathUtils.elapsedMicroSec(startTimeNanos), TimeUnit.MICROSECONDS);
                      logger.debug("Stopped executing {} after {} attempts.", proc, attempts);
                      throw e;
                  }
                  TimeUnit.MILLISECONDS.sleep(retryPolicy.nextRetryWaitTime(attempts, elapsedTime));
              }
          }
          return result;
      }
  
  }
  