Hi Markus,

What group communications are you using?  How were you able to deduce that
the problems were coming from group communications?

Thanks, Robert

On 9/18/08 7:07 AM, "Markus Wolf" <[EMAIL PROTECTED]> wrote:

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> Hi Emmanuel,
>
> we have had do reinitalize the whole cluster. To our luck this was only
> a test environment and no production system.
> After further investigating the problem we tracked it down to an error
> in the controller group communication. We are uploading files in our
> webapp which are afterwards stored as blobs in the database.
> The whole process does work when only one controller is running, but if
> the second controller is active only part of the transaction is
> replicated to the second one and the transaction on both controller hangs.
> The problem also only occurs if the file is larger than 2,7k (at least
> in our tests). We also tested with a 27k file which result in hanging
> transactions.
> No exception is thrown from the controller or no log entry is done.
>
> Is there an option to specify the file limits? Or maybe could it be
> related to our hsqldb recovery log and blob handling?
>
> Thanks for any help
> Markus Wolf
>
>>> we are using Sequoia 2.10.10 and have two controllers on dedicated
>>> systems each with one backend database.
>>> Yesterday I started a backup on controller2 and after that the database
>>> was not enabled again. So I restarted the virtual-database but since
>>> that the controller hangs.
>>> After searching for some info about the problem (no log file entries) I
>>> dicovered that there are 7 pending transactions on controller1 which
>>> seem to block the controller. They do not seem to timeout and I have
>>> found no option to rollback/timeout them with the console or JMX.
>>>
>> Yes, it is true that there is no option in the console to rollback a
>> transaction, this is probably a feature we should add. If you close the
>> client connections (can probably easily be done by resetting the app.
>> side connection pool) that will automatically rollback the connections.
>> Open transactions usually come from an application that does not
>> commit/rollback transactions in all cases (and thus transactions remain
>> uncommitted). Another caveat of the JDBC API is that a commit/rollback
>> automatically starts a new transaction. So if you don't force the
>> connection to setAutoCommit(true) after a commit/rollback they will be
>> in a new transaction. And Sequoia can only perform
>> enable.disable/backup/shutdown operations on transaction boundaries.
>> We never implemented a kill/abort command because it cannot be
>> implemented deterministically (what do you do is the transaction has
>> already committed on a backend and you try to cancel cluster-wide?).
>> This could however be implemented for open transaction with no active
>> request. Feel free to add a feature request in JIRA if you think this
>> could be a useful tool to have.
>>> Am I missing something? Can someone give me a hint on how to stabilize
>>> the system again. Or is the only solution to kill both controllers,
>>> initialize the database again (or restore from dump) and synchronize the
>>> controllers again afterwards?
>>>
>> In your case, the 2nd backend was still in backup mode waiting for
>> transactions to complete. If you are not able to terminate the
>> transactions by closing your application connections, you can reset the
>> virtual database by using a force shutdown (this will abort pending
>> transactions). You will probably have to resynchronize the 2nd
>> controller with its backend upon restart to make sure that they are
>> properly synchronized.
>>
>> Hope this helps,
>> Emmanuel
>>
>
>
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--
Robert Hodges, CTO, Continuent, Inc.
Email:  [EMAIL PROTECTED]
Mobile:  +1-510-501-3728  Skype:  hodgesrm


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