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 storm.trident.spout;
  
  import java.util.Map;
  
  import backtype.storm.task.TopologyContext;
  import backtype.storm.tuple.Fields;
  import storm.trident.operation.TridentCollector;
  import storm.trident.topology.TransactionAttempt;
  
  public interface ITridentSpout<T> extends ITridentDataSource {
      interface BatchCoordinator<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 JSON encoding to store the metadata.  Only simple types
           * such as numbers, booleans, strings, lists, and maps should be used.
           * 
           * @param txid The id of the transaction.
           * @param prevMetadata The metadata of the previous transaction
           * @param currMetadata The metadata for this transaction the last time it was initialized.
           *                     null if this is the first attempt
           * @return the metadata for this new transaction
           */
          X initializeTransaction(long txid, X prevMetadata, X currMetadata);
  
          /**
           * This attempt committed successfully, so all state for this commit and before can be safely cleaned up.
           *
           * @param txid transaction id that completed
           */
          void success(long txid);
  
          /**
           * hint to Storm if the spout is ready for the transaction id
           *
           * @param txid the id of the transaction
           * @return true, if the spout is ready for the given transaction id
           */
          boolean isReady(long txid);
  
          /**
           * 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 initializeTransaction method. This method must always emit
           * the same batch of tuples across all tasks for the same transaction id.
           * @param tx transaction id
           * @param coordinatorMeta metadata from the coordinator defining this transaction
           * @param collector output tuple collector
           */
          void emitBatch(TransactionAttempt tx, X coordinatorMeta, TridentCollector collector);
          
          /**
           * This attempt committed successfully, so all state for this commit and before can be safely cleaned up.
           * @param tx attempt object containing transaction id and attempt number
           */
          void success(TransactionAttempt tx);
  
          /**
           * 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. The Coordinator that you provide in a TransactionalSpout provides metadata for each
       * transaction so that the transactions can be replayed in case of failure.
       *
       * Two instances are requested, one on the master batch coordinator where isReady() is called, and an instance
       * in the coordinator bolt which is used for all other operations. The two instances do not necessarily share a
       * worker JVM.
       *
       * @param txStateId stream id
       * @param conf Storm config map
       * @param context topology context
       * @return spout coordinator instance
       */
      BatchCoordinator<T> getCoordinator(String txStateId, 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.
       *
       * All emitter tasks get the same transaction metadata. The topology context parameter contains the instance
       * task id that can be used to distribute the work across the tasks.
       *
       * @param txStateId stream id
       * @param conf Storm config map
       * @param context topology context
       * @return spout emitter
       */
      Emitter<T> getEmitter(String txStateId, Map conf, TopologyContext context); 
      
      Map<String, Object> getComponentConfiguration();
      Fields getOutputFields();
  }
  