philipnee commented on code in PR #12672: URL: https://github.com/apache/kafka/pull/12672#discussion_r998532115
########## clients/src/main/java/org/apache/kafka/clients/consumer/internals/DefaultBackgroundThread.java: ########## @@ -0,0 +1,226 @@ +/* + * 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.CommonClientConfigs; +import org.apache.kafka.clients.consumer.ConsumerConfig; +import org.apache.kafka.clients.consumer.internals.events.ApplicationEvent; +import org.apache.kafka.clients.consumer.internals.events.BackgroundEvent; +import org.apache.kafka.clients.consumer.internals.events.NoopApplicationEvent; +import org.apache.kafka.common.KafkaException; +import org.apache.kafka.common.errors.InterruptException; +import org.apache.kafka.common.errors.WakeupException; +import org.apache.kafka.common.metrics.Metrics; +import org.apache.kafka.common.utils.KafkaThread; +import org.apache.kafka.common.utils.LogContext; +import org.apache.kafka.common.utils.Time; +import org.apache.kafka.common.utils.Utils; +import org.slf4j.Logger; + +import java.util.Optional; +import java.util.concurrent.BlockingQueue; +import java.util.concurrent.atomic.AtomicReference; + +/** + * Background thread runnable that consumes {@code ApplicationEvent} and + * produces {@code BackgroundEvent}. It uses an event loop to consume and + * produce events, and poll the network client to handle network IO. + * + * It holds a reference to the {@link SubscriptionState}, which is + * initialized by the polling thread. + */ +public class DefaultBackgroundThread extends KafkaThread { + private static final String BACKGROUND_THREAD_NAME = + "consumer_background_thread"; + private final Time time; + private final Logger log; + private final BlockingQueue<ApplicationEvent> applicationEventQueue; + private final BlockingQueue<BackgroundEvent> backgroundEventQueue; + private final ConsumerNetworkClient networkClient; + private final SubscriptionState subscriptions; + private final ConsumerMetadata metadata; + private final Metrics metrics; + private final ConsumerConfig config; + + private String clientId; + private long retryBackoffMs; + private int heartbeatIntervalMs; + private boolean running; + private Optional<ApplicationEvent> inflightEvent = Optional.empty(); + private final AtomicReference<Optional<RuntimeException>> exception = + new AtomicReference<>(Optional.empty()); + + public DefaultBackgroundThread(ConsumerConfig config, + LogContext logContext, + BlockingQueue<ApplicationEvent> applicationEventQueue, + BlockingQueue<BackgroundEvent> backgroundEventQueue, + SubscriptionState subscriptions, + ConsumerMetadata metadata, + ConsumerNetworkClient networkClient, + Metrics metrics) { + this(Time.SYSTEM, + config, + logContext, + applicationEventQueue, + backgroundEventQueue, + subscriptions, + metadata, + networkClient, + metrics); + } + + public DefaultBackgroundThread(Time time, + ConsumerConfig config, + LogContext logContext, + BlockingQueue<ApplicationEvent> applicationEventQueue, + BlockingQueue<BackgroundEvent> backgroundEventQueue, + SubscriptionState subscriptions, + ConsumerMetadata metadata, + ConsumerNetworkClient networkClient, + Metrics metrics) { + super(BACKGROUND_THREAD_NAME, true); + try { + this.time = time; + this.log = logContext.logger(DefaultBackgroundThread.class); + this.applicationEventQueue = applicationEventQueue; + this.backgroundEventQueue = backgroundEventQueue; + this.config = config; + setConfig(); + this.inflightEvent = Optional.empty(); + // subscriptionState is initialized by the polling thread + this.subscriptions = subscriptions; + this.metadata = metadata; + this.networkClient = networkClient; + this.metrics = metrics; + this.running = true; + } catch (Exception e) { + // now propagate the exception + close(); + throw new KafkaException("Failed to construct background processor", e); + } + } + + private void setConfig() { + this.retryBackoffMs = this.config.getLong(ConsumerConfig.RETRY_BACKOFF_MS_CONFIG); + this.clientId = config.getString(CommonClientConfigs.CLIENT_ID_CONFIG); + this.heartbeatIntervalMs = config.getInt(ConsumerConfig.HEARTBEAT_INTERVAL_MS_CONFIG); + } + + @Override + public void run() { + try { + log.debug("{} started", getClass()); + while (running) { + try { + runOnce(); + } catch (WakeupException | InterruptException e) { + log.debug("Exception thrown, background thread won't " + + "terminate", e); + // swallow + } + } + } catch (Throwable t) { + log.error("The background thread failed due to unexpected error", + t); + if (t instanceof RuntimeException) + this.exception.set(Optional.of((RuntimeException) t)); Review Comment: We could, there are other places in the code that uses RTE so trying to be consistent with the existing code. -- This is an automated message from the Apache Git Service. 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