[Engine-devel] Global transaction in ovirt-engine

[Yair Zaslavsky]

----- Original Message -----
> From: "Michael Kublin" <mkublin at redhat.com>
> To: "engine-devel" <engine-devel at ovirt.org>
> Sent: Tuesday, February 12, 2013 4:59:19 PM
> Subject: Re: [Engine-devel] Global transaction in ovirt-engine
> 
> 
> 
> ----- Original Message -----
> > From: "Omer Frenkel" <ofrenkel at redhat.com>
> > To: "Michael Kublin" <mkublin at redhat.com>
> > Cc: "engine-devel" <engine-devel at ovirt.org>
> > Sent: Tuesday, February 12, 2013 4:32:44 PM
> > Subject: Re: [Engine-devel] Global transaction in ovirt-engine
> > 
> > 
> > 
> > ----- Original Message -----
> > > From: "Michael Kublin" <mkublin at redhat.com>
> > > To: "engine-devel" <engine-devel at ovirt.org>
> > > Sent: Tuesday, February 12, 2013 11:38:33 AM
> > > Subject: [Engine-devel] Global transaction in ovirt-engine
> > > 
> > > The issue is a following (I think I had raised it once),
> > > by default when any command is invoked in ovirt-engine a
> > > transaction
> > > is opened.
> > > Now, lets take a look on complicated command which is performing
> > > a
> > > lot of XML-RPC/HTTP calls and just simple update ,
> > > such command is a main cause for the following problems:
> > > 1. Long transactions, each call increase a time of transaction
> > > 2. When transaction is opened a connection which is associated
> > > with
> > > it also in used, so a number of available DB connections reduced
> > > from
> > > connection pool.
> > > 3. A errors : transaction was cancelled and operation is failed
> > > on
> > > engine side, but successes at host side.
> > > 4. Performance - "try to keep transactions as short as possible".
> > > 5. Performance - to many unneeded transactions
> > > 6. Bug debugging - it is very difficult to understand why
> > > something
> > > was committed and something not why transaction was reverted or
> > > not,
> > >    when we have a lot of nested transactions.
> > > 
> > > Now, what should be done by my opinion:
> > > 1. Change default behaviour - by default not to open a
> > > transaction
> > > (Today, transaction is opened and if we don't want a command
> > > should
> > > be marked
> > >    by NonTransactiveCommandAttribute) - it is simple
> > > 2. The change described at 1 will require to rewrite and redesign
> > > some flows - more difficult, but also can be done pretty fast.
> > >    By the way this can be or even should be done at any case.
> > > 3. All new commands should not be based on global transaction or
> > > keep
> > > in mind that global transaction can be disabled
> > > 
> > > Benefits,
> > > 1. Better performance
> > > 2. Cleaner code
> > > 3. Less bugs
> > > 4. Increased scale
> > > 
> > > Regards Michael
> > > _______________________________________________
> > > Engine-devel mailing list
> > > Engine-devel at ovirt.org
> > > http://lists.ovirt.org/mailman/listinfo/engine-devel
> > > 
> > 
> > need to remember that transaction also gave us 10-min limit for
> > command execution,
> > not saying its good or bad, but disabling the transactions will
> > allow
> > commands to run forever,
> > this 10 min limit actually, saved us few times when commands got
> > stuck in all kind of locks etc..
> > 
> Not exactly, if transaction has expired the JBOSS transaction
> framework (Arjuna)
> will not stop a running thread attached to such thread.
> We can configure it in such way that a running thread will be
> cancelled, but for now
> it is not.

So current behavior is somewhat "unexpected" - it all determines if the thread will try to use the transaction after it was "reaped off" from him.
Right?
If this is the case - I think this is bad.
Do we have a real requirement for commands to end their execution phase at 10 minutes? 

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