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.util;
  
  import java.util.Map;
  import java.util.concurrent.RejectedExecutionException;
  import org.apache.bookkeeper.common.util.MdcUtils;
  import org.apache.bookkeeper.common.util.OrderedExecutor;
  import org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallback;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.slf4j.MDC;
  
  /**
   * Generic callback implementation which will run the
   * callback in the thread which matches the ordering key.
   */
  public abstract class OrderedGenericCallback<T> implements GenericCallback<T> {
      private static final Logger LOG = LoggerFactory.getLogger(OrderedGenericCallback.class);
  
      private final OrderedExecutor executor;
      private final long orderingKey;
      private final Map<String, String> mdcContextMap;
  
      /**
       * @param executor The executor on which to run the callback
       * @param orderingKey Key used to decide which thread the callback
       *                    should run on.
       */
      public OrderedGenericCallback(OrderedExecutor executor, long orderingKey) {
          this.executor = executor;
          this.orderingKey = orderingKey;
          this.mdcContextMap = executor.preserveMdc() ? MDC.getCopyOfContextMap() : null;
      }
  
      @Override
      public final void operationComplete(final int rc, final T result) {
          MdcUtils.restoreContext(mdcContextMap);
          try {
              // during closing, callbacks that are error out might try to submit to
              // the scheduler again. if the submission will go to same thread, we
              // don't need to submit to executor again. this is also an optimization for
              // callback submission
              if (Thread.currentThread().getId() == executor.getThreadID(orderingKey)) {
                  safeOperationComplete(rc, result);
              } else {
                  try {
                      executor.executeOrdered(orderingKey, new Runnable() {
                          @Override
                          public void run() {
                              safeOperationComplete(rc, result);
                          }
  
                          @Override
                          public String toString() {
                              return String.format("Callback(key=%s, name=%s)",
                                      orderingKey,
                                      OrderedGenericCallback.this);
                          }
                      });
                  } catch (RejectedExecutionException re) {
                      LOG.warn("Failed to submit callback for {} : ", orderingKey, re);
                  }
              }
          } finally {
              MDC.clear();
          }
      }
  
      public abstract void safeOperationComplete(int rc, T result);
  }
  