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From "Michael Chen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (AMQ-2929) Compressed text message received by consumer uncompressed
Date Tue, 09 Nov 2010 01:59:00 GMT

    [ https://issues.apache.org/activemq/browse/AMQ-2929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=63188#action_63188
] 

Michael Chen commented on AMQ-2929:
-----------------------------------

Latest findings
============
An unconsumed message in a queue is decompressed when a JMX client code calls "browse()" on
that Queue's MBean. Below is a stack trace captured by Eclipse (sorry about not having full
class names).

"ActiveMQMonitorModule ... line: 86" is where our code calls the "browse" method of the Queue's
MBean. This led to "ActiveMQTextMessage.getText() line: 83", which decompressed the message,
allocating large amount of memory, and possibly killing the broker altogether.

Another side effect is that the message is permanently decompressed in the queue, and due
to the other bug mentioned in my 9/22 comment, the consumer receives a message that is decompressed
but with the wrong (isCompressed() == true) result.

Our work-around is to call the MBean's "browseMessages()" with the patch for AMQ-3023. However,
if you use JConsole to browse the unconsumed messages, it too will trigger the decompression
of messages (possibly killing the broker due to out of memory). A nasty booby trap.

One possible fix is for OpenTypeSupport.TextMessageOpenTypeFactory.getFields(Object) to check
for m.isCompressed(), and if true not to call m.getText().  See line 367 of OpenTypeSupport.java.

{code}
Thread [SelfMonitor] (Evaluating)	
	InflaterInputStream(InputStream) line: 91 [local variables unavailable]
	ActiveMQTextMessage.getText() line: 83 [local variables unavailable]	
	OpenTypeSupport$TextMessageOpenTypeFactory.getFields(Object) line: 367	
	OpenTypeSupport.convert(Message) line: 397	
	QueueView(DestinationView).browse(String) line: 151	
	QueueView(DestinationView).browse() line: 132	
	GeneratedMethodAccessor43.invoke(Object, Object[]) line: not available	
	DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 25	
	Method.invoke(Object, Object...) line: 597	
	StandardMBeanIntrospector.invokeM2(Method, Object, Object[], Object) line: 93	
	StandardMBeanIntrospector.invokeM2(Object, Object, Object[], Object) line: 27	
	StandardMBeanIntrospector(MBeanIntrospector<M>).invokeM(M, Object, Object[], Object)
line: 208	
	PerInterface<M>.invoke(Object, String, Object[], String[], Object) line: 120	
	StandardMBeanSupport(MBeanSupport<M>).invoke(String, Object[], String[]) line: 262

	AnnotatedMBean(StandardMBean).invoke(String, Object[], String[]) line: 391	
	DefaultMBeanServerInterceptor.invoke(ObjectName, String, Object[], String[]) line: 836	
	JmxMBeanServer.invoke(ObjectName, String, Object[], String[]) line: 761	
	ActiveMQMonitorModule$1QueueValueAccessor.getValue() line: 86	
	ActiveMQMonitorModule$1QueueValueAccessor.getValue() line: 67	
	BaseModuleAttribute<D>.getCurrentValue() line: 106	
	ActiveMQMonitorModule(BaseMonitorModule).getCurrentModuleData() line: 105	
	MonitorData.populateModuleData(MonitorModule) line: 195	
	MonitorGenerator.process() line: 135	
	BaseRouteBuilder$1.run() line: 81	
	BaseRouteBuilder$2.run() line: 176	
	TimerThread.mainLoop() line: 512	
	TimerThread.run() line: 462	
{code}

> Compressed text message received by consumer uncompressed
> ---------------------------------------------------------
>
>                 Key: AMQ-2929
>                 URL: https://issues.apache.org/activemq/browse/AMQ-2929
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.3.2
>         Environment: ActiveMQ 5.3.2 / Camel 2.2.0
>            Reporter: Michael Chen
>         Attachments: ActiveMQConsumerTest.java, ActiveMQConsumerTest.xml, ActiveMQProducerTest.java,
ActiveMQProducerTest.xml
>
>
> I have a queue setup to send and consume compressed text messages.  This is done via
Spring setting ActiveMQConnectionFactory.useCompression to true.  If the consumer connects
to this queue before the first message is arrives, everything works great.
> If the messages are sent to this queue before the consumer connects, those early messages
will cause ZipException "unknown compression method" when consumed by the belated consumer.
Debugger shows that the ActiveMQTextMessage.content already contains the uncompressed text
(with 4 leading length bytes) when ActiveMQTextMessage.getText() is called.
> If I set useCompression to false, early messages are consumed with no problems.  Please
look into this.
> I notice that after ActiveMQTextMessage.getText() decompress the message, it does not
set compressed to false. Not sure if that is the cause.

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