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/*
* Copyright 2016 dorkbox, llc
*
* Licensed 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 dorkbox.messagebus.synchrony;
import dorkbox.messagebus.util.NamedThreadFactory;
import dorkbox.messagebus.error.ErrorHandler;
import dorkbox.messagebus.error.PublicationError;
import dorkbox.messagebus.dispatch.Dispatch;
import dorkbox.messagebus.synchrony.disruptor.MessageType;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.locks.LockSupport;
/**
* By default, it is the calling thread that has to get the subscriptions, which the sync/async logic then uses.
*
* The exception to this rule is when checking/calling DeadMessage publication.
*
* This is similar in behavior to the disruptor in that it does not generate garbage, however the downside of this implementation is it is
* slow, but faster than other messagebus implementations.
*
* Basically, the disruptor is fast + noGC.
*
* @author dorkbox, llc Date: 2/3/16
*/
public final
class AsyncABQ_noGc implements Synchrony {
private final ArrayBlockingQueue dispatchQueue;
// have two queues to prevent garbage, So we pull off one queue to add to another queue and when done, we put it back
private final ArrayBlockingQueue gcQueue;
private final Collection threads;
private final Collection shutdown;
private final ErrorHandler errorHandler;
/**
* Notifies the consumers during shutdown that it's on purpose.
*/
private volatile boolean shuttingDown = false;
public
AsyncABQ_noGc(final int numberOfThreads, final ErrorHandler errorHandler) {
this.errorHandler = errorHandler;
this.dispatchQueue = new ArrayBlockingQueue(1024);
this.gcQueue = new ArrayBlockingQueue(1024);
// this is how we prevent garbage
for (int i = 0; i < 1024; i++) {
gcQueue.add(new MessageHolder());
}
// each thread will run forever and process incoming message publication requests
Runnable runnable = new Runnable() {
@SuppressWarnings({"ConstantConditions", "UnnecessaryLocalVariable"})
@Override
public
void run() {
final ArrayBlockingQueue IN_QUEUE = AsyncABQ_noGc.this.dispatchQueue;
final ArrayBlockingQueue OUT_QUEUE = AsyncABQ_noGc.this.gcQueue;
final ErrorHandler errorHandler1 = errorHandler;
while (!AsyncABQ_noGc.this.shuttingDown) {
process(IN_QUEUE, OUT_QUEUE, errorHandler1);
}
synchronized (shutdown) {
shutdown.add(Boolean.TRUE);
}
}
};
this.threads = new ArrayDeque(numberOfThreads);
this.shutdown = new ArrayList();
final NamedThreadFactory threadFactory = new NamedThreadFactory("MessageBus");
for (int i = 0; i < numberOfThreads; i++) {
Thread thread = threadFactory.newThread(runnable);
this.threads.add(thread);
thread.start();
}
}
@SuppressWarnings("Duplicates")
private
void process(final ArrayBlockingQueue queue,
final ArrayBlockingQueue gcQueue, final ErrorHandler errorHandler) {
MessageHolder event;
int messageType = MessageType.ONE;
Dispatch dispatch;
Object message1 = null;
Object message2 = null;
Object message3 = null;
try {
event = queue.take();
messageType = event.type;
dispatch = event.dispatch;
message1 = event.message1;
message2 = event.message2;
message3 = event.message3;
gcQueue.put(event);
switch (messageType) {
case MessageType.ONE: {
dispatch.publish(message1);
return;
}
case MessageType.TWO: {
dispatch.publish(message1, message2);
return;
}
case MessageType.THREE: {
dispatch.publish(message1, message2, message3);
//noinspection UnnecessaryReturnStatement
return;
}
}
} catch (InterruptedException e) {
if (!this.shuttingDown) {
switch (messageType) {
case MessageType.ONE: {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message dequeue.")
.setCause(e)
.setPublishedObject(message1));
return;
}
case MessageType.TWO: {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message dequeue.")
.setCause(e)
.setPublishedObject(message1, message2));
return;
}
case MessageType.THREE: {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message dequeue.")
.setCause(e)
.setPublishedObject(message1, message2, message3));
//noinspection UnnecessaryReturnStatement
return;
}
}
}
}
}
@Override
public
void publish(final Dispatch dispatch, final Object message1) {
try {
MessageHolder job = gcQueue.take();
job.type = MessageType.ONE;
job.dispatch = dispatch;
job.message1 = message1;
this.dispatchQueue.put(job);
} catch (InterruptedException e) {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message queue.")
.setCause(e)
.setPublishedObject(message1));
}
}
@Override
public
void publish(final Dispatch dispatch, final Object message1, final Object message2) {
try {
MessageHolder job = gcQueue.take();
job.type = MessageType.TWO;
job.dispatch = dispatch;
job.message1 = message1;
job.message2 = message2;
this.dispatchQueue.put(job);
} catch (InterruptedException e) {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message queue.")
.setCause(e)
.setPublishedObject(message1, message2));
}
}
@Override
public
void publish(final Dispatch dispatch, final Object message1, final Object message2, final Object message3) {
try {
MessageHolder job = gcQueue.take();
job.type = MessageType.THREE;
job.dispatch = dispatch;
job.message1 = message1;
job.message2 = message2;
job.message3 = message3;
this.dispatchQueue.put(job);
} catch (InterruptedException e) {
errorHandler.handlePublicationError(new PublicationError().setMessage("Interrupted error during message queue.")
.setCause(e)
.setPublishedObject(message1, message2, message3));
}
}
@Override
public
boolean hasPendingMessages() {
return !this.dispatchQueue.isEmpty();
}
@SuppressWarnings("Duplicates")
@Override
public
void shutdown() {
this.shuttingDown = true;
for (Thread t : this.threads) {
t.interrupt();
}
while (true) {
synchronized (shutdown) {
if (shutdown.size() == threads.size()) {
return;
}
LockSupport.parkNanos(100L); // wait 100ms for threads to quit
}
}
}
}
