[GitHub] [rocketmq-clients] lizhimins commented on a diff in pull request #342: Add API of PullConsumer

["lizhimins (via GitHub)" <gi...@apache.org>]

lizhimins commented on code in PR #342:
URL: https://github.com/apache/rocketmq-clients/pull/342#discussion_r1124298004


##########
java/client-apis/src/main/java/org/apache/rocketmq/client/apis/consumer/PullConsumer.java:
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@@ -0,0 +1,136 @@
+/*
+ * 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.rocketmq.client.apis.consumer;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.time.Duration;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import org.apache.rocketmq.client.apis.ClientException;
+import org.apache.rocketmq.client.apis.message.MessageQueue;
+import org.apache.rocketmq.client.apis.message.MessageView;
+
+public interface PullConsumer extends Closeable {
+    /**
+     * Get the consumer group of the consumer.
+     */
+    String getConsumerGroup();
+
+    /**
+     * @param topic    the topic that needs to be monitored.
+     * @param listener the callback to detect the message queue changes.
+     */
+    void registerMessageQueueChangeListenerByTopic(String topic, TopicMessageQueueChangeListener listener);
+
+    /**
+     * Fetch message queues of the topic.
+     */
+    Collection<MessageQueue> fetchMessageQueues(String topic) throws ClientException;
+
+    /**
+     * Manually assign a list of message queues to this consumer.
+     *
+     * <p>This interface does not allow for incremental assignment and will replace the previous assignment (if
+     * previous assignment existed).
+     *
+     * @param messageQueues the list of message queues that are to be assigned to this consumer.
+     */
+    void assign(Collection<MessageQueue> messageQueues);
+
+    /**
+     * Fetch messages from assigned message queues specified by {@link #assign(Collection)}.
+     *
+     * <p>The messages polled from remote are across the message queue.
+     *
+     * @param timeout the maximum time to block.
+     * @return list of fetched messages.
+     */
+    List<MessageView> poll(Duration timeout);
+
+    /**
+     * Overrides the fetch offsets that the consumer will use on the next poll. If this method is invoked for the same
+     * message queue more than once, the latest offset will be used on the next {@link #poll(Duration)}.
+     *
+     * @param messageQueue the message queue to override the fetch offset.
+     * @param offset       message offset.
+     */
+    void seek(MessageQueue messageQueue, long offset);
+
+    /**
+     * Suspending message pulling from the message queues.
+     *
+     * @param messageQueues message queues that need to be suspended.
+     */
+    void pause(Collection<MessageQueue> messageQueues);
+
+    /**
+     * Resuming message pulling from the message queues.
+     *
+     * @param messageQueues message queues that need to be resumed.
+     */
+    void resume(Collection<MessageQueue> messageQueues);
+
+    /**
+     * Look up the offsets for the given message queue by timestamp. The returned offset for each message queue is the
+     * earliest offset whose timestamp is greater than or equal to the given timestamp in the corresponding message
+     * queue.
+     *
+     * @param messageQueue message queue that needs to be looked up.
+     * @param timestamp    the timestamp for which to search.
+     * @return the offset of the message queue, or {@link Optional#empty()} if there is no message.
+     */
+    Optional<Long> offsetForTimestamp(MessageQueue messageQueue, Long timestamp);
+
+    /**
+     * Get the latest committed offset for the given message queue.
+     *
+     * @return the latest committed offset, or {@link Optional#empty()} if there was no prior commit.
+     */
+    Optional<Long> committed(MessageQueue messageQueue);
+
+    /**
+     * Commit offset manually.
+     */
+    void commit() throws ClientException;

Review Comment:
   commit 的语义不明确，比如说对于单个队列客户端 pull 进度是 200，poll 此时返回了 100，我们是不知道消费进度的，此时 commit 200 那就丢消息了，commit 100 也不对，对用户来说并不是说前一批消息消费完才能来拿下一批。所以这里的含义是 auto commit。对于流框架来说，通常希望 commit 和 ckpt 是原子的，我认为还应该增加 commit(mq, offset) 作为手动接口。



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