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[CDO] High level change notifications between clients [message #1752045]

Wed, 18 January 2017 09:26

Marcus Rosell

Messages: 3
Registered: January 2017
Location: Gothenburg, Sweden

Junior Member

Hi.
We're in the process of moving our RCP application to CDO from a XMI-based resource.
For the RCP-application we use long running CDO transactions and a lot of commands can have been executed before a commit.

Today we process the complete change notification set, and dig out, what parts of the GUI and which Caches we need to update. This has proven quite cumbersome and, in some cases, impossible to do reliably.

Because of this, we have identified that we need to communicate some kind of "high level" change events to the other clients. Is there a way to send such messages through CDO?

Best regards
Marcus

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Re: [CDO] High level change notifications between clients [message #1752087 is a reply to message #1752045]

Wed, 18 January 2017 16:54

Eike Stepper

Messages: 6682
Registered: July 2009

Senior Member

Yes, you can use CDORemoteSessionManager.sendMessage() to broadcast messages to all subscribed remote sessions or CDORemoteSession.sendMessage() to send a a message to a single remote session. The API is explained in http://download.eclipse.org/modeling/emf/cdo/drops/R20160607-1209/help/org.eclipse.emf.cdo.doc/javadoc/org/eclipse/emf/cdo/session/remote/package-summary.html

If you need even more (full) control you can register your own Net4j protocol and multiplex it through a channel of the connection that's used by CDO. A file upload expample is explained in https://thegordian.blogspot.de/2008/12/remoting-with-iprogressmonitor.html

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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Re: [CDO] High level change notifications between clients [message #1752132 is a reply to message #1752087]

Thu, 19 January 2017 07:19

Marcus Rosell

Messages: 3
Registered: January 2017
Location: Gothenburg, Sweden

Junior Member

Thanks.
Timing wise, lets say that I commit a transaction and afterward I do a sendMessage(), will the other clients receive, first, the change notifications and later the messages?
Will the events be fired in the "correct" order?

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Re: [CDO] High level change notifications between clients [message #1752136 is a reply to message #1752132]

Thu, 19 January 2017 07:53

Eike Stepper

Messages: 6682
Registered: July 2009

Senior Member

No, there's no guarantee about the order in which these different types of signals arrive at other clients. Only the correct order of commit notifications is guaranteed.

But you can achieve the correct ordering yourself with not much effort. Capture the commit timestamp with transaction.commit().getTimeStamp() or CDOTransaction.getLastCommitTime() and encode it into the CDORemoteMessage that you'll send to the other clients. The receiving clients decode the timestamp from the message and call transaction.waitForUpdate(timestamp) before they act upon the rest of the message.

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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