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Bug 370979

Summary: New API for opening Transactions on a specific branch with durable locking ID
Product: [Modeling] EMF Reporter: Alex Lagarde <alex.lagarde>
Component: cdo.coreAssignee: Project Inbox <emf.cdo-inbox>
Status: CLOSED WORKSFORME QA Contact:
Severity: enhancement    
Priority: P3 CC: stepper
Version: 4.1   
Target Milestone: ---   
Hardware: PC   
OS: Windows 7   
Whiteboard:

Description Alex Lagarde CLA 2012-02-08 12:03:04 EST 
Hi everyone !

I'm currently playing with CDO branches, and I noticed that CDO does not provide API for opening transaction with durable locking ID on specific branches.

http://download.eclipse.org/modeling/emf/cdo/drops/I20120203-0410/help/org.eclipse.emf.cdo.doc/javadoc/org/eclipse/emf/cdo/transaction/CDOTransactionContainer.html

If there is no technical reason explaining this limitation, I think that the following methods should be added to CDOTransactionContainer : 
- openTransaction(String durableLockingID, CDOBranch branch, ResourceSet resourceSet)
- openTransaction(String durableLockingID, CDOBranch branch)

Alex
Comment 1 Eike Stepper CLA 2012-02-08 12:29:02 EST 
Hi Alex,

Locks are generally scoped to a specific branch and can not be transfered to other branches. In addition to the absence of API for that there are server side checks to prevent from accidentally "reinterpreting" locks from other branches. This is by design and I can not see a reason why one would like to relax that. I'm closing this as WONTFIX until someone can explain to me why moving locks between branches makes sense.

Please note that durable locks really lock objects in a branch to a view/owner. That ownership can be transfered to other views, but nothing else.
Comment 2 Alex Lagarde CLA 2012-02-09 02:30:15 EST 
Hi Eike,

thanks for your fast reply.

If I open a transaction on a branch b1, with enableLockindID() == true, and then try to reopen it later using my lockingID, will the transaction be opened automatically on the branch b1 ? If this is the case then the existing API fulfill my need.

I agree with you that transfering locks from one branch to another does not have any sense.
Comment 3 Eike Stepper CLA 2012-02-09 06:43:23 EST 
Yes, this code in CDOViewImpl shows it:

  protected void doActivate() throws Exception
  {
    CDOSessionProtocol sessionProtocol = session.getSessionProtocol();
    if (durableLockingID != null)
    {
      CDOBranchPoint branchPoint = sessionProtocol.openView(viewID, isReadOnly(), durableLockingID);
      basicSetBranchPoint(branchPoint);
    }
    else
    {
      sessionProtocol.openView(viewID, isReadOnly(), this);
    }
  }

;-)