philipnee commented on code in PR #12672: URL: https://github.com/apache/kafka/pull/12672#discussion_r998527530
########## 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)); + else + this.exception.set(Optional.of(new RuntimeException(t))); + } finally { + close(); + log.debug("{} closed", getClass()); + } + } + + /** + * Process event from a single poll + */ + void runOnce() { + this.inflightEvent = maybePollEvent(); + log.debug("processing application event: {}", this.inflightEvent); + if (this.inflightEvent.isPresent() && maybeConsumeInflightEvent(this.inflightEvent.get())) { + // clear inflight event upon successful consumption + this.inflightEvent = Optional.empty(); + } + + // if there are pending events to process, poll then continue without + // blocking. + if (!applicationEventQueue.isEmpty() || inflightEvent.isPresent()) { + networkClient.poll(time.timer(0)); + return; + } + // if there are no events to process, poll until timeout. The timeout + // will be the minimum of the requestTimeoutMs, nextHeartBeatMs, and + // nextMetadataUpdate. See NetworkClient.poll impl. + networkClient.poll(time.timer(timeToNextHeartbeatMs(time.milliseconds()))); + } + + private long timeToNextHeartbeatMs(long nowMs) { + // TODO: implemented when heartbeat is added to the impl + return 100; + } + + private Optional<ApplicationEvent> maybePollEvent() { + if (this.inflightEvent.isPresent() || this.applicationEventQueue.isEmpty()) { + return this.inflightEvent; + } + return Optional.ofNullable(this.applicationEventQueue.poll()); + } + + /** + * ApplicationEvent are consumed here. + * @param event an {@link ApplicationEvent} + * @return true when successfully consumed the event. + */ + private boolean maybeConsumeInflightEvent(ApplicationEvent event) { + log.debug("try consuming event: {}", Optional.ofNullable(event)); + switch (event.type) { + case NOOP: + process((NoopApplicationEvent) event); + return true; + default: + inflightEvent = Optional.empty(); + log.warn("unsupported event type: {}", event.type); + return true; + } + } + + /** + * Processes {@link NoopApplicationEvent} and equeue a + * {@link NoopBackgroundEvent}. This is intentionally left here for + * demonstration purpose. + * @param event a {@link NoopApplicationEvent} + */ + private void process(NoopApplicationEvent event) { + backgroundEventQueue.add(new NoopBackgroundEvent(event.message)); + } + + public boolean isRunning() { + return this.running; + } + + public void wakeup() { + networkClient.wakeup(); + } + + public void close() { + this.wakeup(); + this.running = false; + Utils.closeQuietly(networkClient, "consumer network client"); + Utils.closeQuietly(metadata, "consumer network client"); Review Comment: thanks... copy paste error -- 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
