kirktrue commented on code in PR #14670: URL: https://github.com/apache/kafka/pull/14670#discussion_r1378275567
########## clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerDelegateCreator.java: ########## @@ -0,0 +1,132 @@ +/* + * 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.internals; + +import org.apache.kafka.clients.consumer.Consumer; +import org.apache.kafka.clients.consumer.ConsumerConfig; +import org.apache.kafka.clients.consumer.KafkaConsumer; +import org.apache.kafka.common.KafkaException; +import org.apache.kafka.common.serialization.Deserializer; + +import java.util.Map; +import java.util.Properties; +import java.util.function.Supplier; + +/** + * {@code ConsumerDelegateCreator} implements a quasi-factory pattern to allow the caller to remain unaware of the + * underlying {@link Consumer} implementation that is created. This provides the means by which {@link KafkaConsumer} + * can remain the top-level facade for implementations, but allow different implementations to co-exist under + * the covers. + * + * <p/> + * + * The current logic for the {@code ConsumerCreator} inspects the incoming configuration and determines if + * it is using the new KIP-848 consumer protocol or if it should fall back to the existing, legacy group protocol. + * This is based on the presence and value of the {@code group.protocol} configuration value. If the value is present + * and equals {@code consumer}, the {@link AsyncKafkaConsumer} will be returned. Otherwise, the + * {@link LegacyKafkaConsumer} will be returned. + * + * <p/> + * + * This is not to be called by end users and callers should not attempt to determine the underlying implementation + * as this will make such code very brittle. Users of this facility should honor the top-level {@link Consumer} API + * contract as-is. + */ +public class ConsumerDelegateCreator { + + /** + * This is it! This is the core logic. It's extremely rudimentary. + */ + private static boolean useNewConsumer(Map<?, ?> configs) { + Object groupProtocol = configs.get("group.protocol"); + + // Takes care of both the null and type checks. + if (!(groupProtocol instanceof String)) + return false; + + return ((String) groupProtocol).equalsIgnoreCase("consumer"); + } + + public <K, V> Consumer<K, V> create(Map<String, Object> configs) { + return createInternal(() -> { + if (useNewConsumer(configs)) { + return new AsyncKafkaConsumer<>(configs); + } else { + return new LegacyKafkaConsumer<>(configs); + } + }); + } + + public <K, V> Consumer<K, V> create(Properties properties) { + return createInternal(() -> { + if (useNewConsumer(properties)) { + return new AsyncKafkaConsumer<>(properties); + } else { + return new LegacyKafkaConsumer<>(properties); + } + }); + } + + public <K, V> Consumer<K, V> create(Properties properties, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(properties)) { + return new AsyncKafkaConsumer<>(properties, keyDeserializer, valueDeserializer); + } else { + return new LegacyKafkaConsumer<>(properties, keyDeserializer, valueDeserializer); + } + }); + } + + public <K, V> Consumer<K, V> create(Map<String, Object> configs, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(configs)) { + return new AsyncKafkaConsumer<>(configs, keyDeserializer, valueDeserializer); + } else { + return new LegacyKafkaConsumer<>(configs, keyDeserializer, valueDeserializer); + } + }); + } + + public <K, V> Consumer<K, V> create(ConsumerConfig config, + Deserializer<K> keyDeserializer, + Deserializer<V> valueDeserializer) { + return createInternal(() -> { + if (useNewConsumer(config.values())) { Review Comment: Yep. I don't really care for it, either. As above, I wanted to preserve a 1:1 mapping between the constructor that was invoked in `KafkaConsumer` and the constructor in the delegate. If we feel that's overkill, we can change it. -- 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
