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Date: Tue, 30 Oct 2012 22:36:12 +0000 (UTC)
From: "Stirling Chow (JIRA)" <jira@apache.org>
To: dev@activemq.apache.org
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In-Reply-To: <1557548802.47192.1351635492329.JavaMail.jiratomcat@arcas>
Subject: [jira] [Updated] (AMQ-4147) Memory usage incorrectly updated across
 network of brokers when VMTransport is used.
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     [ https://issues.apache.org/jira/browse/AMQ-4147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stirling Chow updated AMQ-4147:
-------------------------------

    Attachment: AMQ4147Test.java

Unit test demonstrating issue on VM transport, but no problem with TCP transport
                
> Memory usage incorrectly updated across network of brokers when VMTransport is used.
> ------------------------------------------------------------------------------------
>
>                 Key: AMQ-4147
>                 URL: https://issues.apache.org/jira/browse/AMQ-4147
>             Project: ActiveMQ
>          Issue Type: Bug
>    Affects Versions: 5.8.0
>            Reporter: Stirling Chow
>         Attachments: AMQ4147Test.java
>
>
> Symptom
> =======
> I was writing some unit tests based on {{org.apache.activemq.JmsMultipleBrokersTestSupport}}, and noticed the following issue:
> When brokers are connected in a network using VMTransport (i.e., VMTransport on both the local and remote ends of a bridge), and a message moves from broker1 to broker2, the memory usage of the message continues to be accounted for on broker1 until the message is actually consumed on broker2.  
> If the brokers are bridged using a non-VM transport (e.g., TCP), memory usage on broker1 is reduced as soon as the message is bridged to broker2, and broker2's memory usage increases until the message is consumed.
> Cause
> =====
> The cause is the same as in AMQ-4116: {{Message.copy()}} copies the {{memoryUsage}} object.  As a result, when the message moves from broker1 to broker2, the original {{memoryUsage}} object, which refers to broker1 is copied through to broker2 and never updated to broker2's {{memoryUsage}} object.
> Specifically, the message is copied from the local transport before being sent to the remote transport by this code:
> {code:title=DemandForwardingBridgeSupport.java}
> protected void serviceLocalCommand(Command command) {
>     if (!disposed.get()) {
>         try {
>             if (command.isMessageDispatch()) {
>                 enqueueCounter.incrementAndGet();
>                 final MessageDispatch md = (MessageDispatch) command;
>                 final DemandSubscription sub = subscriptionMapByLocalId.get(md.getConsumerId());
>                 if (sub != null && md.getMessage() != null && sub.incrementOutstandingResponses()) {
>                     if (suppressMessageDispatch(md, sub)) {
>                         if (LOG.isDebugEnabled()) {
>                             LOG.debug(configuration.getBrokerName() + " message not forwarded to " + remoteBrokerName + " because message came from there or fails networkTTL, brokerPath: " + Arrays.toString(md.getMessage().getBrokerPath()) + ", message: " + md.getMessage());
>                         }
>                         // still ack as it may be durable
>                         try {
>                             localBroker.oneway(new MessageAck(md, MessageAck.INDIVIDUAL_ACK_TYPE, 1));
>                         } finally {
>                             sub.decrementOutstandingResponses();
>                         }
>                         return;
>                     }
>                     Message message = configureMessage(md);
> ...
> protected Message configureMessage(MessageDispatch md) {
>     Message message = md.getMessage().copy();
> ...
> {code}
> This bug is not present when a non-VM transport is used for the bridge because {{Message.memoryUsage}} is marked transient *not* copied during serialization/deserialization over the transport.
> Solution
> ========
> Since this is at least the second bug to result from the current {{Message.copy()}} behaviour, I think "Solution 1" proposed from AMQ-4116 is starting to look attractive as both a solution to AMQ-4116 and this bug:
> Modify {{Message.copy()}} so that it sets the resulting message's {{memoryUsage}} object to {{null}}.  This would make {{Message.copy()}} behave more similarly to serialization/deserialization.

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