当队列有n个待处理消息时，ActiveMQ不返回消息

Environment/Background:

环境/背景:

Using PHP Stomp library to send and receive message from ActiveMQ (v5.4.3).

使用PHP Stomp库从ActiveMQ (v5.4.3)发送和接收消息。

Steps:

步骤:

Client sends a message with reply-to & correlation-id headers to request queue (say /queue/request)
客户端向请求队列发送具有应答和关联id头的消息(例如/queue/request)
Subscribe to the response queue (say /queue/response)
订阅响应队列(例如/队列/响应)
Read frame
阅读框架
ack
消
unsubscribe
退订

The above steps works fine when there is no pending message or pending message < n. In my case, n =200. When the number of pending message is > 200, the message is not delivered. The process waits till timeout and finally timeout without response. I can see the message (using admin UI) after timeout. Here is the code that I'm using for this case:

当没有等待消息或等待消息< n时，上述步骤可以正常工作。在我的例子中，n =200。当挂起消息的数量为>200时，该消息不会被传递。进程等待超时，最后超时而没有响应。超时后我可以看到消息(使用admin UI)。这是我在这个案例中使用的代码:

<?php

// make a connection
$con = new Stomp("tcp://localhost:61616");
// Set read timeout.
$con->setReadTimeout(10);

// Prepare request variables.
$correlation_id = rand();    
$request_queue = '/queue/com.domain.service.request';
$response_queue = '/queue/com.domain.service.response';
$selector =  "JMSCorrelationID='$correlation_id'";
$headers = array('correlation-id' => $correlation_id, 'reply-to' => $response_queue);
$message = '<RequestBody></RequestBody>';

// send a message to the queue.
$con->send($request_queue, $message, $headers);

// subscribe to the queue
$con->subscribe($response_queue, array('selector' => $selector, 'ack' => 'auto'));

// receive a message from the queue
$msg = $con->readFrame();

// do what you want with the message
if ( $msg != null) {
    echo "Received message with body\n";
    var_dump($msg);
    // mark the message as received in the queue
    $con->ack($msg);
} else {
    echo "Failed to receive a message\n";
}
unset($con);

Other findings:

其他的发现:

Sending messages from one file (say from sender.php) and receive using another script (say receiver.php) working fine.

从一个文件(比如sender.php)发送消息，然后使用另一个脚本(比如receiver.php)接收消息，效果很好。
Allows to send more than 1000 message in the same request queue(and eventually processed and placed in response queue). So it doesn't look like memory issue.

允许在同一个请求队列中发送超过1000条消息(并最终处理并放置在响应队列中)。看起来不像是记忆问题。
Funny enough, while waiting for timeout, if I browse the queue on admin UI, I get the response.

有趣的是，在等待超时时，如果我在admin UI上浏览队列，就会得到响应。
By default, the stomp broker that I use set the prefetch size to 1.

默认情况下，我使用的stomp代理将预取大小设置为1。

2 个解决方案

#1

Without knowing more my guess is that you have multiple consumers and one is hogging the messages in it's prefetch buffer, the default size is 1000 I think. To debug situations like this it's usually a good idea to look at the web console or connect with jconsole and inspect the Queue MBean to see the stats for in-flight messages, number of consumers etc.

我不知道的是，您有多个消费者，其中一个在它的预取缓冲区中占用消息，我认为默认大小是1000。要调试这样的情况，最好查看web控制台或连接jconsole并检查队列MBean，以查看航班消息的统计信息、用户数量等。

#2

Answering my own question.

回答我的问题。

The problem I'm facing is exactly what is described in http://trenaman.blogspot.co.uk/2009/01/message-selectors-and-activemq.html and the solution is to increase the maxPageSize as specified in ActiveMQ and maxPageSize

我所面临的问题正是在http://trenaman.blogspot.co.uk/2009/01/message- selectorand -activemq中所描述的问题。html和解决方案是增加ActiveMQ和maxPageSize中指定的maxPageSize

As you can match that the 200 is not a varying number, but the default value of maxPageSize.

正如您可以匹配的那样，200不是一个变化的数字，而是maxPageSize的默认值。

More references:

更多的引用:

http://activemq.2283324.n4.nabble.com/Consumer-is-not-able-to-pick-messages-from-queue-td2531722.html

http://activemq.2283324.n4.nabble.com/Consumer-is-not-able-to-pick-messages-from-queue-td2531722.html
https://issues.apache.org/jira/browse/AMQ-2217

https://issues.apache.org/jira/browse/amq - 2217
https://issues.apache.org/jira/browse/AMQ-2745

https://issues.apache.org/jira/browse/amq - 2745

#1

#2