content: /*
   * Copyright 2022 Alibaba Group Holding Limited.
   *
   * Licensed 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 com.alibaba.graphscope.example.giraph;
  
  import org.apache.giraph.conf.LongConfOption;
  import org.apache.giraph.graph.BasicComputation;
  import org.apache.giraph.graph.Vertex;
  import org.apache.hadoop.io.LongWritable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.util.Objects;
  
  /**
   * Only send msg.
   */
  public class MessageApp
          extends BasicComputation<LongWritable, LongWritable, LongWritable, LongWritable> {
  
      public static LongConfOption MAX_SUPER_STEP;
      private static Logger logger = LoggerFactory.getLogger(MessageApp.class);
  
      static {
          String maxSuperStep = System.getenv("MAX_SUPER_STEP");
          if (Objects.isNull(maxSuperStep) || maxSuperStep.isEmpty()) {
              MAX_SUPER_STEP = new LongConfOption("maxSuperStep", 1, "max super step");
          } else {
              MAX_SUPER_STEP =
                      new LongConfOption(
                              "maxSuperStep", Long.valueOf(maxSuperStep), "max super step");
          }
      }
  
      /**
       * Must be defined by user to do computation on a single Vertex.
       *
       * @param vertex   Vertex
       * @param messages Messages that were sent to this vertex in the previous superstep. Each
       *                 message is only guaranteed to have
       */
      @Override
      public void compute(
              Vertex<LongWritable, LongWritable, LongWritable> vertex,
              Iterable<LongWritable> messages)
              throws IOException {
          if (getSuperstep() == 0) {
              logger.info("There should be no messages in step0, " + vertex.getId());
              boolean flag = false;
              for (LongWritable message : messages) {
                  flag = true;
              }
              if (flag) {
                  throw new IllegalStateException(
                          "Expect no msg received in step 1, but actually received");
              }
              LongWritable msg = new LongWritable(vertex.getId().get());
              sendMessageToAllEdges(vertex, msg);
          } else if (getSuperstep() < MAX_SUPER_STEP.get(getConf())) {
              logger.info("step [{}] Checking received msg", getSuperstep());
              int msgCnt = 0;
              for (LongWritable message : messages) {
                  msgCnt += 1;
              }
              vertex.setValue(new LongWritable(msgCnt));
          } else if (getSuperstep() == MAX_SUPER_STEP.get(getConf())) {
              vertex.voteToHalt();
          } else {
              logger.info("Impossible: " + getSuperstep());
          }
      }
  }
  