storm-client/src/jvm/org/apache/storm/grouping/CustomStreamGrouping.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 org.apache.storm.grouping;

import java.io.Serializable;
import java.util.List;
import org.apache.storm.generated.GlobalStreamId;
import org.apache.storm.task.WorkerTopologyContext;

public interface CustomStreamGrouping extends Serializable {

    /**
     * Tells the stream grouping at runtime the tasks in the target bolt. This information should be used in chooseTasks to determine the
     * target tasks.
     *
     * <p>It also tells the grouping the metadata on the stream this grouping will be used on.
     */
    void prepare(WorkerTopologyContext context, GlobalStreamId stream, List<Integer> targetTasks);

    /**
     * This function implements a custom stream grouping. It takes in as input the number of tasks in the target bolt in prepare and returns
     * the tasks to send the tuples to.
     *
     * @param values the values to group on
     */
    List<Integer> chooseTasks(int taskId, List<Object> values);
}