CallbackHandler.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 io.jafka.producer.async;

import java.util.List;
import java.util.Properties;

/**
 * Callback handler APIs for use in the async producer. The purpose is to
 * give the user some callback handles to insert custom functionality at
 * various stages as the data flows through the pipeline of the async
 * producer
 *
 * @author adyliu (imxylz@gmail.com)
 * @see AbstractCallbackHandler
 * @since 1.0
 */
public interface CallbackHandler<T> {

    /**
     * Initializes the callback handler using a Properties object
     *
     * @param properties properties used to initialize the callback handler
     */
    void init(Properties properties);

    /**
     * Callback to process the data before it enters the batching queue of
     * the asynchronous producer
     *
     * @param data the data sent to the producer
     * @return the processed data that enters the queue or null
     */
    QueueItem<T> beforeEnqueue(QueueItem<T> data);

    /**
     * Callback to process the data right after it enters the batching
     * queue of the asynchronous producer
     *
     * @param data  the data sent to the producer after {@link #beforeEnqueue(QueueItem)}
     * @param added flag that indicates if the data was successfully added
     *              to the queue
     * @return the data
     */
    QueueItem<T> afterEnqueue(QueueItem<T> data, boolean added);

    /**
     * Callback to process the data item right after it has been dequeued
     * by the background sender thread of the asynchronous producer
     *
     * @param data the data item dequeued from the async producer queue
     * @return the processed list of data items that gets added to the data
     * handled by the event handler
     */
    List<QueueItem<T>> afterDequeuingExistingData(QueueItem<T> data);

    /**
     * Callback to process the batched data right before it is being sent
     * by the handle API of the event handler
     *
     * @param data the batched data received by the event handler
     * @return the processed batched data that gets sent by the handle()
     * API of the event handler
     */
    List<QueueItem<T>> beforeSendingData(List<QueueItem<T>> data);

    /**
     * Callback to process the last batch of data right before the producer
     * send thread is shutdown
     *
     * @return the last batch of data that is sent to the EventHandler
     */
    List<QueueItem<T>> lastBatchBeforeClose();

    /**
     * Cleans up and shuts down the callback handler
     */
    void close();
}