guozhangwang commented on code in PR #13265: URL: https://github.com/apache/kafka/pull/13265#discussion_r1115047665
########## clients/src/main/java/org/apache/kafka/clients/consumer/StubbedAsyncKafkaConsumer.java: ########## @@ -0,0 +1,548 @@ +/* + * 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.kafka.clients.consumer; + +import org.apache.kafka.clients.consumer.internals.Fetcher; +import org.apache.kafka.clients.consumer.internals.SubscriptionState; +import org.apache.kafka.clients.consumer.internals.NoOpConsumerRebalanceListener; +import org.apache.kafka.clients.consumer.internals.events.ApplicationEventProcessor; +import org.apache.kafka.clients.consumer.internals.events.AssignPartitionsEvent; +import org.apache.kafka.clients.consumer.internals.events.CommitAsyncEvent; +import org.apache.kafka.clients.consumer.internals.events.CommitSyncEvent; +import org.apache.kafka.clients.consumer.internals.events.EventHandler; +import org.apache.kafka.clients.consumer.internals.events.FetchCommittedOffsetsEvent; +import org.apache.kafka.clients.consumer.internals.events.FetchOffsetsEvent; +import org.apache.kafka.clients.consumer.internals.events.FetchRecordsEvent; +import org.apache.kafka.clients.consumer.internals.events.RequestRebalanceEvent; +import org.apache.kafka.clients.consumer.internals.events.SubscribePatternEvent; +import org.apache.kafka.clients.consumer.internals.events.SubscribeTopicsEvent; +import org.apache.kafka.clients.consumer.internals.events.UnsubscribeEvent; +import org.apache.kafka.common.Metric; +import org.apache.kafka.common.MetricName; +import org.apache.kafka.common.PartitionInfo; +import org.apache.kafka.common.TopicPartition; +import org.apache.kafka.common.errors.InvalidGroupIdException; +import org.apache.kafka.common.errors.RecordDeserializationException; +import org.apache.kafka.common.header.Headers; +import org.apache.kafka.common.header.internals.RecordHeaders; +import org.apache.kafka.common.record.Record; +import org.apache.kafka.common.record.TimestampType; +import org.apache.kafka.common.requests.ListOffsetsRequest; +import org.apache.kafka.common.serialization.Deserializer; +import org.apache.kafka.common.utils.Time; +import org.apache.kafka.common.utils.Timer; +import org.apache.kafka.common.utils.Utils; + +import java.nio.ByteBuffer; +import java.time.Duration; +import java.util.Collection; +import java.util.Collections; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.Optional; +import java.util.OptionalLong; +import java.util.Set; +import java.util.regex.Pattern; + +/** + * This {@link StubbedAsyncKafkaConsumer stub} implementation of {@link Consumer} serves as a <i>wireframe</i> or + * <i>sketch</i>, showing the interaction between the foreground and background threads. Each of the main API methods + * will need to answer the following questions: + * + * <ol> + * <li>Does this method block?</li> + * <li>Does this method interact with the background thread?</li> + * <li>If yes, what data is passed as input to the background thread?</li> + * <li>If yes, what data is returned as output from the background thread?</li> + * </ol> + * + * @param <K> Key + * @param <V> Value + * @see ApplicationEventProcessor for the logic of the background event handler + */ +public class StubbedAsyncKafkaConsumer<K, V> implements Consumer<K, V> { + + /** + * These instance variables are intentionally left unassigned, to avoid clutter... + */ + private Time time; + + private EventHandler eventHandler; + + private SubscriptionState subscriptions; + + private Deserializer<K> keyDeserializer; + + private Deserializer<V> valueDeserializer; + + private long defaultApiTimeoutMs; + + private List<ConsumerPartitionAssignor> assignors; + + private Optional<String> groupId; + + /** + * Answers to the above questions: + * + * <ol> + * <li>No</li> + * <li>No</li> + * <li><i>n/a</i></li> + * <li><i>n/a</i></li> + * </ol> + */ + @Override + public Set<TopicPartition> assignment() { Review Comment: In the `assign()` -> `assignment()` example above, there is no "rebalance" triggered and hence there's no rebalance listener triggered either. The rebalance listener is only relevant with the `subscribe()` scenarios. So just to summarize all the scenarios here to avoid confusions between us :) 1. `assign()`: the followed `assignment()` should always reflect the latest partition list from the previous `assign()`, and also the followed `poll()` should return data from the latest partition list only (i.e. the background thread, upon getting this new partition list, should cleanup the buffered records accordingly, and the followed `poll` call should return empty data if no new data is retrieved within the poll timeout yet). 2. `subscribe()`: the followed `assignment()` could potentially still return current assignment which is inconsistent with the `subscribe()` --- this is the case today, but as I mentioned above I think could be open for discussion whether we can to change --- or return the new assignment after the rebalance if enough time has elapsed so that the rebalance is done; the followed `poll()` though should also only return data from the latest partition list as a result of the new subscription. 3. `seek/seekToB/E`: the followed `position` should reflect the newly set position, and also the followed `poll` should only return data from the new seeking position. -- This is an automated message from the Apache Git Service. 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