philipnee commented on code in PR #13265: URL: https://github.com/apache/kafka/pull/13265#discussion_r1114928370
########## 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: I feel we need an explicit synchronization barrier to ensure state changes happen in a deterministic sequence. I mentioned this idea in our previous meeting, but I just want to bring it up again for discussion: (feel free to strike down this idea) Is it reasonable to ask users to invoke poll() after any sort of assignment to trigger the rebalance? I think we could use poll() as an explicit barrier to synchronize both threads. So back to your example, 1. User updates assignment via `assign()` 2. Read calls (`assignments()`) here will still returns the previous state 3. client invoke poll() - update client and background state and triggers rebalance. Rebalance callback triggered. 4. `assignments()` returns the updated version of the assignment. Invalid fetches will be dropped here. I think it kind of breaks the current contract, as `assign()` -> `assignment()` should already reflect to the current assignment. But I do think regardless of how we handle this, there will be some kind of behavioral changes as the threading model is now asynchronous, which kind of implies data update is expected to be asynchronous. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
