jstorm-core/src/main/java/backtype/storm/transactional/partitioned/IPartitionedTransactionalSpout.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 backtype.storm.transactional.partitioned;

import backtype.storm.task.TopologyContext;
import backtype.storm.topology.IComponent;
import backtype.storm.transactional.TransactionAttempt;
import backtype.storm.coordination.BatchOutputCollector;
import java.util.Map;

/**
 * This interface defines a transactional spout that reads its tuples from a partitioned set of brokers. It automates the storing of metadata for each partition
 * to ensure that the same batch is always emitted for the same transaction id. The partition metadata is stored in Zookeeper.
 */
public interface IPartitionedTransactionalSpout<T> extends IComponent {
    public interface Coordinator {
        /**
         * Return the number of partitions currently in the source of data. The idea is is that if a new partition is added and a prior transaction is replayed,
         * it doesn't emit tuples for the new partition because it knows how many partitions were in that transaction.
         */
        int numPartitions();

        /**
         * 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();

        void close();
    }

    public interface Emitter<X> {
        /**
         * Emit a batch of tuples for a partition/transaction that's never been emitted before. Return the metadata that can be used to reconstruct this
         * partition/batch in the future.
         */
        X emitPartitionBatchNew(TransactionAttempt tx, BatchOutputCollector collector, int partition, X lastPartitionMeta);

        /**
         * Emit a batch of tuples for a partition/transaction that has been emitted before, using the metadata created when it was first emitted.
         */
        void emitPartitionBatch(TransactionAttempt tx, BatchOutputCollector collector, int partition, X partitionMeta);

        void close();
    }

    Coordinator getCoordinator(Map conf, TopologyContext context);

    Emitter<T> getEmitter(Map conf, TopologyContext context);
}