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 backtype.storm.transactional;
  
  import backtype.storm.coordination.BatchOutputCollector;
  import backtype.storm.task.TopologyContext;
  import backtype.storm.topology.IComponent;
  import java.math.BigInteger;
  import java.util.Map;
  
  public interface ITransactionalSpout<T> extends IComponent {
      interface Coordinator<X> {
          /**
           * Create metadata for this particular transaction id which has never been emitted before. The metadata should contain whatever is necessary to be able
           * to replay the exact batch for the transaction at a later point.
           *
           * The metadata is stored in Zookeeper.
           *
           * Storm uses the Kryo serializations configured in the component configuration for this spout to serialize and deserialize the metadata.
           *
           * @param txid         The id of the transaction.
           * @param prevMetadata The metadata of the previous transaction
           * @return the metadata for this new transaction
           */
          X initializeTransaction(BigInteger txid, X prevMetadata);
  
          /**
           * Returns true if its ok to emit start a new transaction, false otherwise (will skip this transaction).
           *
           * You should sleep here if you want a delay between asking for the next transaction (this will be called repeatedly in a loop).
           */
          boolean isReady();
  
          /**
           * Release any resources from this coordinator.
           */
          void close();
      }
  
      interface Emitter<X> {
          /**
           * Emit a batch for the specified transaction attempt and metadata for the transaction. The metadata was created by the Coordinator in the
           * initializeTranaction method. This method must always emit the same batch of tuples across all tasks for the same transaction id.
           *
           * The first field of all emitted tuples must contain the provided TransactionAttempt.
           */
          void emitBatch(TransactionAttempt tx, X coordinatorMeta, BatchOutputCollector collector);
  
          /**
           * Any state for transactions prior to the provided transaction id can be safely cleaned up, so this method should clean up that state.
           */
          void cleanupBefore(BigInteger txid);
  
          /**
           * Release any resources held by this emitter.
           */
          void close();
      }
  
      /**
       * The coordinator for a TransactionalSpout runs in a single thread and indicates when batches of tuples should be emitted and when transactions should
       * commit. The Coordinator that you provide in a TransactionalSpout provides metadata for each transaction so that the transactions can be replayed.
       */
      Coordinator<T> getCoordinator(Map conf, TopologyContext context);
  
      /**
       * The emitter for a TransactionalSpout runs as many tasks across the cluster. Emitters are responsible for emitting batches of tuples for a transaction and
       * must ensure that the same batch of tuples is always emitted for the same transaction id.
       */
      Emitter<T> getEmitter(Map conf, TopologyContext context);
  }
  