org.apache.rocketmq.client.java.misc.Dispatcher Maven / Gradle / Ivy
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* 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.rocketmq.client.java.misc;
import org.apache.rocketmq.shaded.com.google.common.util.concurrent.AbstractIdleService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.apache.rocketmq.shaded.org.slf4j.Logger;
import org.apache.rocketmq.shaded.org.slf4j.LoggerFactory;
/**
* A driver to notify downstream to dispatch task.
*
* Data flows from the upstream worker to the downstream processor, but there are many worker threads from
* upstream which produce data concurrently, and the downstream processor could process the data quickly, so it is
* not necessary for all workers to trigger the downstream task. To address this issue, there is a task queue whose
* capacity is 1.
*
*
The invocation of {@link #notify()} from upstream is collected, once there is no task existed in task queue,
* new task is created and delivered into the task queue, or the existed task in the queue could ensure the data workers
* represented is processed by {@link #dispatch()} in time.
*
*
* ┌───────────┐
* │ processor │
* └──────▲────┘
* │ dispatch
* │
* ┌───┴──┐
* │ │ task queue
* │ │
* │size=1│
* │ │
* ┌─────────►│ ◄──────────┐
* notify │ └───▲──┘ │
* │ notify │ notify │
* ┌───┴────┐ ┌────┴───┐ ┌────┴───┐
* │ worker │ │ worker │ │ worker │
* └────────┘ └────────┘ └────────┘
*
*/
public abstract class Dispatcher extends AbstractIdleService {
private static final Logger LOGGER = LoggerFactory.getLogger(Dispatcher.class);
private final String clientId;
/**
* Flag indicates that whether task is queued or not.
*/
private final AtomicBoolean dispatched;
private final ThreadPoolExecutor dispatcherExecutor;
public Dispatcher(String clientId) {
this.clientId = clientId;
this.dispatched = new AtomicBoolean(false);
this.dispatcherExecutor = new ThreadPoolExecutor(
1,
1,
60,
TimeUnit.SECONDS,
new LinkedBlockingQueue<>(),
new ThreadFactoryImpl("Dispatcher"));
}
@Override
public void startUp() {
}
@Override
public void shutDown() throws InterruptedException {
dispatcherExecutor.shutdown();
if (!ExecutorServices.awaitTerminated(dispatcherExecutor)) {
LOGGER.error("[Bug] Failed to shutdown the batch dispatcher, clientId={}", clientId);
}
}
/**
* The implementation should never ever throw any exception.
*/
public abstract void dispatch();
/**
* Signal downstream to execute {@link #dispatch()} in time.
*/
public void signal() {
if (dispatched.compareAndSet(false, true)) {
try {
dispatcherExecutor.submit(() -> {
dispatched.compareAndSet(true, false);
try {
dispatch();
} catch (Throwable t) {
LOGGER.error("Exception raised while dispatching task, clientId={}", clientId, t);
}
});
} catch (Throwable t) {
if (!dispatcherExecutor.isShutdown()) {
LOGGER.error("[Bug] Failed to submit dispatch task, clientId={}", clientId, t);
}
}
}
}
}