/**
    * 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.hadoop.hbase.ipc;
  
  import java.util.Deque;
  import java.util.concurrent.BlockingQueue;
  import java.util.concurrent.ConcurrentLinkedDeque;
  import java.util.concurrent.atomic.AtomicInteger;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Abortable;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * RPC Executor that extends {@link RWQueueRpcExecutor} with fast-path feature, used in
   * {@link FastPathBalancedQueueRpcExecutor}.
   */
  @InterfaceAudience.LimitedPrivate({ HBaseInterfaceAudience.COPROC, HBaseInterfaceAudience.PHOENIX})
  @InterfaceStability.Evolving
  public class FastPathRWQueueRpcExecutor extends RWQueueRpcExecutor {
    private static final Logger LOG = LoggerFactory.getLogger(RWQueueRpcExecutor.class);
  
    private final Deque<FastPathRpcHandler> readHandlerStack = new ConcurrentLinkedDeque<>();
    private final Deque<FastPathRpcHandler> writeHandlerStack = new ConcurrentLinkedDeque<>();
    private final Deque<FastPathRpcHandler> scanHandlerStack = new ConcurrentLinkedDeque<>();
  
    public FastPathRWQueueRpcExecutor(String name, int handlerCount, int maxQueueLength,
      PriorityFunction priority, Configuration conf, Abortable abortable) {
      super(name, handlerCount, maxQueueLength, priority, conf, abortable);
    }
  
    @Override
    protected RpcHandler getHandler(final String name, final double handlerFailureThreshhold,
      final int handlerCount, final BlockingQueue<CallRunner> q,
      final AtomicInteger activeHandlerCount, final AtomicInteger failedHandlerCount,
      final Abortable abortable) {
      Deque<FastPathRpcHandler> handlerStack = name.contains("read") ? readHandlerStack :
        name.contains("write") ? writeHandlerStack : scanHandlerStack;
      return new FastPathRpcHandler(name, handlerFailureThreshhold, handlerCount, q,
        activeHandlerCount, failedHandlerCount, abortable, handlerStack);
    }
  
    @Override
    public boolean dispatch(final CallRunner callTask) throws InterruptedException {
      RpcServer.Call call = callTask.getCall();
      boolean shouldDispatchToWriteQueue = isWriteRequest(call.getHeader(), call.param);
      boolean shouldDispatchToScanQueue = shouldDispatchToScanQueue(callTask);
      FastPathRpcHandler handler = shouldDispatchToWriteQueue ? writeHandlerStack.poll() :
        shouldDispatchToScanQueue ? scanHandlerStack.poll() : readHandlerStack.poll();
      return handler != null ? handler.loadCallRunner(callTask) :
        dispatchTo(shouldDispatchToWriteQueue, shouldDispatchToScanQueue, callTask);
    }
  }