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Posted to dev@activemq.apache.org by "Chris Dolan (Created) (JIRA)" <ji...@apache.org> on 2012/03/19 21:51:38 UTC
[jira] [Created] (AMQ-3776) synchronization error in
MessageListenerServlet.getAjaxWebClient
synchronization error in MessageListenerServlet.getAjaxWebClient
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Key: AMQ-3776
URL: https://issues.apache.org/jira/browse/AMQ-3776
Project: ActiveMQ
Issue Type: Bug
Affects Versions: 5.5.0
Reporter: Chris Dolan
Priority: Minor
Note: I found this problem by reading code, not by an actual behavior problem!
In the latest revision of MessageListenerServlet.getAjaxWebClient() you can see that the ajaxWebClients map is read outside of a synchronized block and then edited inside the block. This looks like a simple mistake, and the get() should be moved down one line.
http://svn.apache.org/viewvc/activemq/trunk/activemq-web/src/main/java/org/apache/activemq/web/MessageListenerServlet.java?revision=1177026&view=markup#l438
Theoretically, the downside of this bug will be that new clients will be unnecessarily created if a single web session connects to the servlet from two or more concurrent connections. In practice, this almost never happens because most ajax users of ActiveMQ should have only one connection in flight at a time.
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[jira] [Resolved] (AMQ-3776) synchronization error in
MessageListenerServlet.getAjaxWebClient
Posted by "Timothy Bish (Resolved) (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/AMQ-3776?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Timothy Bish resolved AMQ-3776.
-------------------------------
Resolution: Fixed
Fix Version/s: 5.6.0
Assignee: Timothy Bish
Fix applied in trunk.
> synchronization error in MessageListenerServlet.getAjaxWebClient
> ----------------------------------------------------------------
>
> Key: AMQ-3776
> URL: https://issues.apache.org/jira/browse/AMQ-3776
> Project: ActiveMQ
> Issue Type: Bug
> Affects Versions: 5.5.0
> Reporter: Chris Dolan
> Assignee: Timothy Bish
> Priority: Minor
> Fix For: 5.6.0
>
>
> Note: I found this problem by reading code, not by an actual behavior problem!
> In the latest revision of MessageListenerServlet.getAjaxWebClient() you can see that the ajaxWebClients map is read outside of a synchronized block and then edited inside the block. This looks like a simple mistake, and the get() should be moved down one line.
> http://svn.apache.org/viewvc/activemq/trunk/activemq-web/src/main/java/org/apache/activemq/web/MessageListenerServlet.java?revision=1177026&view=markup#l438
> Theoretically, the downside of this bug will be that new clients will be unnecessarily created if a single web session connects to the servlet from two or more concurrent connections. In practice, this almost never happens because most ajax users of ActiveMQ should have only one connection in flight at a time.
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