content: /*
   * Copyright (C) 2010-2101 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.otter.shared.arbitrate.impl.setl.memory;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.util.Assert;
  
  import com.alibaba.otter.shared.arbitrate.impl.setl.ArbitrateFactory;
  import com.alibaba.otter.shared.arbitrate.impl.setl.ExtractArbitrateEvent;
  import com.alibaba.otter.shared.arbitrate.impl.setl.monitor.PermitMonitor;
  import com.alibaba.otter.shared.arbitrate.model.EtlEventData;
  import com.alibaba.otter.shared.arbitrate.model.TerminEventData.TerminType;
  import com.alibaba.otter.shared.common.model.config.channel.ChannelStatus;
  import com.alibaba.otter.shared.common.model.config.enums.StageType;
  
  /**
   * 基于memory的仲裁器实现
   * 
   * @author jianghang 2012-9-27 下午10:05:08
   * @version 4.1.0
   */
  public class ExtractMemoryArbitrateEvent implements ExtractArbitrateEvent {
  
      private static final Logger logger = LoggerFactory.getLogger(ExtractMemoryArbitrateEvent.class);
  
      public EtlEventData await(Long pipelineId) throws InterruptedException {
          Assert.notNull(pipelineId);
  
          PermitMonitor permitMonitor = ArbitrateFactory.getInstance(pipelineId, PermitMonitor.class);
          permitMonitor.waitForPermit();// 阻塞等待授权
  
          MemoryStageController stageController = ArbitrateFactory.getInstance(pipelineId, MemoryStageController.class);
          Long processId = stageController.waitForProcess(StageType.EXTRACT); // 符合条件的processId
  
          ChannelStatus status = permitMonitor.getChannelPermit();
          if (status.isStart()) {// 即时查询一下当前的状态，状态随时可能会变
              return stageController.getLastData(processId);
          } else {
              logger.warn("pipelineId[{}] extract ignore processId[{}] by status[{}],rollback now",
                  new Object[] { pipelineId,
                      processId, status });
              // 进行ROLLBACK，触发释放下processId，信号量及EventStore里面的读位置点。
              // 1)因为MemoryStageController的load是等待processId最小值完成Tranform才继续，如果这里不释放，会一直卡死等待
              // 2)SELECT信号量消耗完selectTask任务会停止3)EventStore里面的读位置点不回置，如果正好队列已经满并且读取了最后，BINLOG新的数据进不来
              stageController.termin(TerminType.ROLLBACK);
              return await(pipelineId);// 递归调用
          }
      }
  
      public void single(EtlEventData data) {
          Assert.notNull(data);
          MemoryStageController stageController = ArbitrateFactory.getInstance(data.getPipelineId(),
                                                                               MemoryStageController.class);
          stageController.single(StageType.EXTRACT, data);// 通知下一个节点
      }
  
  }
  