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/*
* Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file 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 com.amazonaws.services.sqs.buffered;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
import com.amazonaws.AmazonClientException;
import com.amazonaws.handlers.AsyncHandler;
import com.amazonaws.services.sqs.AmazonSQSAsync;
import com.amazonaws.services.sqs.model.ChangeMessageVisibilityRequest;
import com.amazonaws.services.sqs.model.ChangeMessageVisibilityResult;
import com.amazonaws.services.sqs.model.DeleteMessageRequest;
import com.amazonaws.services.sqs.model.DeleteMessageResult;
import com.amazonaws.services.sqs.model.ReceiveMessageRequest;
import com.amazonaws.services.sqs.model.ReceiveMessageResult;
import com.amazonaws.services.sqs.model.SendMessageRequest;
import com.amazonaws.services.sqs.model.SendMessageResult;
/**
* A buffer to operate on an SQS queue. The buffer batches outbound ( {@code SendMessage},
* {@code DeleteMessage}, {@code ChangeMessageVisibility}) requests to the queue and pre-fetches
* messages to receive. In practice, the buffer does almost no work itself, and delegates it to
* SendQueueBufer and ReceiveQueueBuffer classes.
*
* Any errors encountered are passed through to the callers, either as the appropriate Result
* objects or as exceptions.
*
* When the buffer is not used, all internal processing associated with the buffer stops when any
* outstanding request to SQS completes. In that idle state, the buffer uses neither connections nor
* threads.
*
* Instances of {@code QueueBuffer} are thread-safe.
*/
class QueueBuffer {
private final SendQueueBuffer sendBuffer;
private final ReceiveQueueBuffer receiveBuffer;
private final AmazonSQSAsync realSqs;
QueueBufferConfig config;
/**
* This executor that will be shared among all queue buffers. Since a single JVM can access
* hundreds of queues, it won't do to have hundreds of executors spinning up hundreds of threads
* for each queue. The DaemonThreadFactory creates daemon threads, which means they won't block
* the JVM from exiting if only they are still around.
*/
static ExecutorService executor = Executors.newCachedThreadPool(new DaemonThreadFactory());;
QueueBuffer(QueueBufferConfig paramConfig, String url, AmazonSQSAsync sqs) {
realSqs = sqs;
config = paramConfig;
sendBuffer = new SendQueueBuffer(sqs, executor, paramConfig, url);
receiveBuffer = new ReceiveQueueBuffer(sqs, executor, paramConfig, url);
}
/**
* asynchronously enqueues a message to SQS.
*
* @return a Future object that will be notified when the operation is completed; never null
*/
public Future sendMessage(SendMessageRequest request,
AsyncHandler handler) {
QueueBufferCallback callback = null;
if (handler != null) {
callback = new QueueBufferCallback(handler, request);
}
QueueBufferFuture future = sendBuffer.sendMessage(request, callback);
future.setBuffer(this);
return future;
}
/**
* Sends a message to SQS and returns the SQS reply.
*
* @return never null
*/
public SendMessageResult sendMessageSync(SendMessageRequest request) {
Future future = sendMessage(request, null);
return waitForFuture(future);
}
/**
* Asynchronously deletes a message from SQS.
*
* @return a Future object that will be notified when the operation is completed; never null
*/
public Future deleteMessage(DeleteMessageRequest request,
AsyncHandler handler) {
QueueBufferCallback callback = null;
if (handler != null) {
callback = new QueueBufferCallback(handler, request);
}
QueueBufferFuture future = sendBuffer.deleteMessage(request, callback);
future.setBuffer(this);
return future;
}
/**
* Deletes a message from SQS. Does not return until a confirmation from SQS has been received
*
* @return never null
*/
public DeleteMessageResult deleteMessageSync(DeleteMessageRequest request) {
Future future = deleteMessage(request, null);
return waitForFuture(future);
}
/**
* asynchronously adjust a message's visibility timeout to SQS.
*
* @return a Future object that will be notified when the operation is completed; never null
*/
public Future changeMessageVisibility(ChangeMessageVisibilityRequest request,
AsyncHandler handler) {
QueueBufferCallback callback = null;
if (handler != null) {
callback = new QueueBufferCallback(handler, request);
}
QueueBufferFuture future =
sendBuffer.changeMessageVisibility(request, callback);
future.setBuffer(this);
return future;
}
/**
* Changes visibility of a message in SQS. Does not return until a confirmation from SQS has
* been received.
* @return
*/
public ChangeMessageVisibilityResult changeMessageVisibilitySync(ChangeMessageVisibilityRequest request) {
Future future = sendBuffer.changeMessageVisibility(request, null);
return waitForFuture(future);
}
/**
* Submits a request to receive some messages from SQS.
*
* @return a Future object that will be notified when the operation is completed; never null;
*/
public Future receiveMessage(ReceiveMessageRequest rq,
AsyncHandler handler) {
if (canBeRetrievedFromQueueBuffer(rq)) {
QueueBufferCallback callback = null;
if (handler != null) {
callback = new QueueBufferCallback(handler, rq);
}
QueueBufferFuture future = receiveBuffer.receiveMessageAsync(
rq, callback);
future.setBuffer(this);
return future;
} else if (handler != null) {
return realSqs.receiveMessageAsync(rq, handler);
} else {
return realSqs.receiveMessageAsync(rq);
}
}
/**
* Retrieves messages from an SQS queue.
*
* @return never null
*/
public ReceiveMessageResult receiveMessageSync(ReceiveMessageRequest rq) {
Future future = receiveMessage(rq, null);
return waitForFuture(future);
}
/**
* Shuts down the queue buffer. Once this method has been called, the queue buffer is not
* operational and all subsequent calls to it may fail
*/
public void shutdown() {
// send buffer does not require shutdown, only
// shut down receive buffer
receiveBuffer.shutdown();
}
/**
* We prefetch and load results in the buffer by making basic requests. I.E. we don't request
* queue or message attributes and we have a default visibility timeout. If the user's request
* deviates from the basic request we can't fulfill the request directly from the buffer, we
* have to hit SQS directly (Note that when going to SQS directly messages currently in the
* buffer may be unavailable due to the visibility timeout).
*
* @return True if the request can be fulfilled directly from the buffer, false if we have to go
* back to the service to fetch the results
*/
private boolean canBeRetrievedFromQueueBuffer(ReceiveMessageRequest rq) {
return !hasRequestedQueueAttributes(rq) && !hasRequestedMessageAttributes(rq) && isBufferingEnabled()
&& (rq.getVisibilityTimeout() == null);
}
/**
* @return True if request has been configured to return queue attributes. False otherwise
*/
private boolean hasRequestedQueueAttributes(ReceiveMessageRequest rq) {
return rq.getAttributeNames() != null && !rq.getAttributeNames().isEmpty();
}
/**
* @return True if request has been configured to return message attributes. False otherwise
*/
private boolean hasRequestedMessageAttributes(ReceiveMessageRequest rq) {
return rq.getMessageAttributeNames() != null && !rq.getMessageAttributeNames().isEmpty();
}
/**
* @return True if the client has been configured to prefetch batches of messages. False
* otherwise
*/
private boolean isBufferingEnabled() {
return (config.getMaxInflightReceiveBatches() > 0 && config.getMaxDoneReceiveBatches() > 0);
}
/**
* this method carefully waits for futures. If waiting throws, it converts the exceptions to the
* exceptions that SQS clients expect. This is what we use to turn asynchronous calls into
* synchronous ones
*/
private ResultType waitForFuture(Future future) {
ResultType toReturn = null;
try {
toReturn = future.get();
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
AmazonClientException ce = new AmazonClientException(
"Thread interrupted while waiting for execution result");
ce.initCause(ie);
throw ce;
} catch (ExecutionException ee) {
// if the cause of the execution exception is an SQS exception, extract it
// and throw the extracted exception to the clients
// otherwise, wrap ee in an SQS exception and throw that.
Throwable cause = ee.getCause();
if (cause instanceof AmazonClientException) {
throw (AmazonClientException) cause;
}
AmazonClientException ce = new AmazonClientException(
"Caught an exception while waiting for request to complete...");
ce.initCause(ee);
throw ce;
}
return toReturn;
}
/**
* We need daemon threads in our executor so that we don't keep the process running if our
* executor threads are the only ones left in the process.
*/
private static class DaemonThreadFactory implements ThreadFactory {
static AtomicInteger threadCount = new AtomicInteger(0);
public Thread newThread(Runnable r) {
int threadNumber = threadCount.addAndGet(1);
Thread thread = new Thread(r);
thread.setDaemon(true);
thread.setName("SQSQueueBufferWorkerThread-" + threadNumber);
return thread;
}
}
}