[jboss-jira] [JBoss JIRA] Closed: (JBMESSAGING-1120) Data channel from MultiplexerChannelFactory prevents state transfers from other users of the shared channel

[Tim Fox (JIRA)]

     [ http://jira.jboss.com/jira/browse/JBMESSAGING-1120?page=all ]

Tim Fox closed JBMESSAGING-1120.
--------------------------------

    Resolution: Done

> Data channel from MultiplexerChannelFactory prevents state transfers from other users of the shared channel
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: JBMESSAGING-1120
>                 URL: http://jira.jboss.com/jira/browse/JBMESSAGING-1120
>             Project: JBoss Messaging
>          Issue Type: Bug
>          Components: Messaging Core Distributed Support
>    Affects Versions: 1.4.0.GA
>            Reporter: Brian Stansberry
>         Assigned To: Tim Fox
>             Fix For: 1.4.0.SP1
>
>
> JBM's usage of the JGroups JChannelFactory is causing the startup of the AS to hang.
> Problem is JBM's MultiplexerChannelFactory creates the data channel as follows:
> public Channel createDataChannel() throws Exception
> {
>       return (Channel) server.invoke(this.channelFactory, MUX_OPERATION,
>          new Object[]{dataStack, uniqueID + "-DATA", Boolean.TRUE, uniqueID}, MUX_SIGNATURE);
> }
> The Boolean.TRUE argument tells the JGroups multiplexer that a getState() call will be invoked for this service.  JBM never calls getState(), so it *must not* pass Boolean.TRUE.  Valid usages are:
> public Channel createDataChannel() throws Exception
> {
>       String[] simpleMuxSignature = new String[] {"java.lang.String", "java.lang.String"};
>       return (Channel) server.invoke(this.channelFactory, MUX_OPERATION,
>          new Object[]{dataStack, uniqueID + "-DATA"}, simpleMuxSignature);
> }
> or 
> public Channel createDataChannel() throws Exception
> {
>       return (Channel) server.invoke(this.channelFactory, MUX_OPERATION,
>          new Object[]{dataStack, uniqueID + "-DATA", Boolean.FALSE, null}, MUX_SIGNATURE);
> }
> The former invokes a convenience method that delegates to the latter.
> Passing true for the "register_for_state_transfer" param tells JGroups that you will call getState().  If several services create MuxChannels based on the same underlying JChannel, JGroups will try to group together their state transfer calls. If several callers have created mux channels, it will block any initial getState() call until all of the callers call getState(), executing the state transfer when all the getState calls have been invoked. (Each service gets only its own state; the above just describes how JGroups attempts to coordinate things internally.)
> When JBM creates a mux channel with register_for_state_transfer=true and then never calls getState(), any other service that later creates a mux channel on the same underlying channel will not be able to properly execute a state transfer when it calls getState().
> I'll open a JGroups JIRA to get proper javadoc for this interface. It's obviously pretty complex.

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