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[CDO] Some observations after upgrading to the current integration build [message #1826563] Mon, 27 April 2020 07:46 Go to next message
Robert Schulk is currently offline Robert SchulkFriend
Messages: 109
Registered: July 2015
Senior Member
Recently, we upgraded from an old CDO version (R20170614-0227) to a new integration build (I20200410-0100).

First, I would like to thank the CDO team (Eike?) for the work. We are very happy with CDO, especially the new version.

After upgrading, our integration tests found some new potential issues which I would like to discuss.

1.) Occasional exception when updating the security realm. See attachment: stacktrace_1._securityrealm.txt. This happens only in rare cases. But the impact is quite severy for us: repeating the action with a new transaction also fails.

2.) Accessing a resource from a view shortly after a transaction created the resource. See attachment: stacktrace_2_cdoid.txt. The exception points to a CDOResourceFolder which contains the new resource. Maybe this is a problem on our side? Do we need to ensure a proper timeout between a commit and accessing the resource?

3.) Under heavy load, we sometimes see the this exception. See attachment: stacktrace_3_heavyload.txt.

4.) Potentially a false-positive exception? Occurs during heavy load, but seems to have no bad effect on our side. See: stacktrace_4_unknownvalue.txt
Re: [CDO] Some observations after upgrading to the current integration build [message #1834218 is a reply to message #1826563] Thu, 05 November 2020 09:27 Go to previous messageGo to next message
Eike Stepper is currently offline Eike StepperFriend
Messages: 6557
Registered: July 2009
Senior Member
Robert Schulk wrote on Mon, 27 April 2020 09:46
Recently, we upgraded from an old CDO version (R20170614-0227) to a new integration build (I20200410-0100).

First, I would like to thank the CDO team (Eike?) for the work. We are very happy with CDO, especially the new version.


Thank you very much! And sorry for this late reply.

Quote:
After upgrading, our integration tests found some new potential issues which I would like to discuss.

1.) Occasional exception when updating the security realm. See attachment: stacktrace_1._securityrealm.txt. This happens only in rare cases. But the impact is quite severy for us: repeating the action with a new transaction also fails.


That looks like https://bugs.eclipse.org/bugs/show_bug.cgi?id=545114 . I'm very interested in finding and fixing the cause of this problem, but so far I haven't been able to reproduce it. Perhaps you can help with a test case?

Quote:
2.) Accessing a resource from a view shortly after a transaction created the resource. See attachment: stacktrace_2_cdoid.txt. The exception points to a CDOResourceFolder which contains the new resource. Maybe this is a problem on our side? Do we need to ensure a proper timeout between a commit and accessing the resource?


The only view that is updated in sync with a commit is the committing transaction itself. All other views/transaction of all other sessions on all clients are updated asynchronously. You can not expect them to be in sync with the server unless you call CDOView.waitForUpdate(timeStamp), where the timeStamp should be the time of the commit. You can get this timeStamp like so:

CDOCommitInfo info = tx.commit();
long commitTime = info.getTimeStamp();

otherLocalView.waitForUpdate(commitTime);


Quote:
3.) Under heavy load, we sometimes see the this exception. See attachment: stacktrace_3_heavyload.txt.


Unfortunately the stacktrace is slightly out of sync with the current tip of master. But I think that this exception is just an artifact caused by two things happening concurrently:

a) The conflict resolver of a transaction TX is notified about a remote change and is about to handle it.
b) The same transaction TX is currently in state INACTIVE, i.e., has been closed before.

(rest risk: the NPE is caused by event== null, not transaction==null)

If you submit a bugzilla I could try to avoid logging exceptions in this case.

Quote:
4.) Potentially a false-positive exception? Occurs during heavy load, but seems to have no bad effect on our side. See: stacktrace_4_unknownvalue.txt


That looks like https://bugs.eclipse.org/bugs/show_bug.cgi?id=568214 , which I've fixed 10 days ago ;-)


Re: [CDO] Some observations after upgrading to the current integration build [message #1834263 is a reply to message #1834218] Fri, 06 November 2020 08:11 Go to previous messageGo to next message
Robert Schulk is currently offline Robert SchulkFriend
Messages: 109
Registered: July 2015
Senior Member
1) I already tried to create a test case, but I was not able to do so ;). It is most probably some kind of timing issue. Our integration tests run fine 19/20 times. In our live system, we never saw the issue. If I find the time, I will take another run at creating a test case.

2) Yes, thanks. I already found this and it works fine for us now.

3) I will create a bugzilla once we upgraded to a newer cdo version and get a usable stack trace.

4) Sounds good :)
Re: [CDO] Some observations after upgrading to the current integration build [message #1834480 is a reply to message #1834263] Wed, 11 November 2020 07:50 Go to previous message
Robert Schulk is currently offline Robert SchulkFriend
Messages: 109
Registered: July 2015
Senior Member
I upgraded to build S20201104-0901

I can confirm, that 4) is fixed for us.
Also, I could not observe 3) anymore! So I guess it was somehow fixed along the way.

But I have got a new one ;). Whenever we apply a lock (write option in our case) and then close the transaction without explicitly releasing the lock, we sometimes see stacktrace1 and/or stacktrace2. See attachments.

I created this ticket:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=568709
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