merlimat commented on a change in pull request #2471: PIP-23: Pulsar Java Client Interceptors. URL: https://github.com/apache/incubator-pulsar/pull/2471#discussion_r213911333
########## File path: pulsar-client/src/main/java/org/apache/pulsar/client/api/ConsumerInterceptor.java ########## @@ -0,0 +1,96 @@ +/** + * 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.pulsar.client.api; + +import java.util.List; + +/** + * A plugin interface that allows you to intercept (and possibly mutate) + * messages received by the consumer. + * <p> + * A primary use case is to hook into consumer applications for custom + * monitoring, logging, etc. + * <p> + * Exceptions thrown by interceptor methods will be caught, logged, but + * not propagated further. + */ +public interface ConsumerInterceptor<T> extends AutoCloseable { + + /** + * Close the interceptor. + */ + void close(); + + /** + * This is called just before the message is returned by + * {@link Consumer#receive()}, {@link MessageListener#received(Consumer, + * Message)} or the {@link java.util.concurrent.CompletableFuture} returned by + * {@link Consumer#receiveAsync()} completes. + * <p> + * This method is allowed to modify message, in which case the new message + * will be returned. + * <p> + * Any exception thrown by this method will be caught by the caller, logged, + * but not propagated to client. + * <p> + * Since the consumer may run multiple interceptors, a particular + * interceptor's + * <tt>beforeConsume</tt> callback will be called in the order specified by + * {@link ConsumerBuilder#intercept(ConsumerInterceptor[])}. The first + * interceptor in the list gets the consumed message, the following + * interceptor will be passed + * the message returned by the previous interceptor, and so on. Since + * interceptors are allowed to modify message, interceptors may potentially + * get the messages already modified by other interceptors. However building a + * pipeline of mutable + * interceptors that depend on the output of the previous interceptor is + * discouraged, because of potential side-effects caused by interceptors + * potentially failing to modify the message and throwing an exception. + * if one of interceptors in the list throws an exception from + * <tt>beforeConsume</tt>, the exception is caught, logged, + * and the next interceptor is called with the message returned by the last + * successful interceptor in the list, or otherwise the original consumed + * message. + * + * @param message the message to be consumed by the client. + * @return message that is either modified by the interceptor or same message + * passed into the method. + */ + Message<T> beforeConsume(Message<T> message); + + /** + * This is called consumer sends the acknowledgment to the broker. + * + * <p>Any exception thrown by this method will be ignored by the caller. + * + * @param messageId message to ack, null if acknowledge fail. + * @param cause the exception on acknowledge. + */ + void onAcknowledge(MessageId messageId, Throwable cause); Review comment: This should actually only be called when the consumer has been closed. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
