storm-client/src/jvm/org/apache/storm/trident/operation/Operation.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.trident.operation;

import java.io.Serializable;
import java.util.Map;

/**
 * Parent interface for Trident `Filter`s and `Function`s.
 *
 * <p>`Operation` defines two lifecycle methods for Trident components. The `prepare()` method is called once when the `Operation` is first
 * initialized. The `cleanup()` method is called in local mode when the local cluster is being shut down. In distributed mode, the
 * `cleanup()` method is not guaranteed to be called in every situation, but Storm will make a best effort call `cleanup()` whenever
 * possible.
 */
public interface Operation extends Serializable {
    /**
     * Called when the `Operation` is first initialized.
     *
     * @param conf    the Storm configuration map
     * @param context the operation context which provides information such as the number of partitions in the stream, and the current
     *                partition index. It also provides methods for registering operation-specific metrics.
     * @see org.apache.storm.trident.operation.TridentOperationContext
     */
    void prepare(Map<String, Object> conf, TridentOperationContext context);

    /**
     * When running in local mode, called when the local cluster is being shut down.
     */
    void cleanup();
}