giraph-core/src/main/java/org/apache/giraph/utils/PipelineUtils.java

/*
 * 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.giraph.utils;

import io.netty.channel.Channel;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelPipeline;
import io.netty.util.concurrent.EventExecutorGroup;

/**
 * Utility class for ChannelPipeline
 */
public class PipelineUtils {
  /** Do not instantiate. */
  private PipelineUtils() { }

  /**
   * Add a handler to pipeline if it is not already added
   * and configure the handler to use an executor group based on equality
   * of compareTo and handlerName
   *
   * @param handlerName string name of the handler
   * @param handler channelhandler object
   * @param compareTo string name to compare to for executorgroup usage check
   * @param executor executorgroup instance
   * @param channel netty channel
   */
  public static void addLastWithExecutorCheck(String handlerName,
    ChannelHandler handler, String compareTo, EventExecutorGroup executor,
    Channel channel) {
    ChannelPipeline pipeline = channel.pipeline();
    if (channel.pipeline().get(handlerName) != null) {
      return;
    }
    if (compareTo.equals(handlerName)) {
      pipeline.addLast(executor, handlerName, handler);
    } else {
      pipeline.addLast(handlerName, handler);
    }
  }
}