Hi,
Ok, this is a slightly different question than the one I thought you were
asking, and as you say, 2pc is not relevant. Here are my thoughts on your
proposed design:
1. I assume that you do not want to hold transactions open while waiting
for human input. If you need to for some reason, you are apt to be in
trouble under high load as all those open transactions consume server
resources for unknown and long periods of time.
2. I like to think of the architecture of applications like this, in 5
layers.
presentation layer (what do I see)----------- jsp
presentation manager (workflow control, what do I see next) ------------
servlet
service subsystem (business logic, data manipulation) -------------session
ejb
model subsystem (data model, system state) -------------------entity ejb
persistence subsystem ---------(jdbc, db)
I find this really clears up most of my questions about where to put code,
and makes changes much simpler and more local. In this framework, I
haven't found a case where knowledge of transactions need to get above the
business logic layer. I would be curious to know if you have an example
where this is appropriate.
Thanks
david jencks
On 2001.06.16 21:07:20 -0400 Phan Anh Tran wrote:
> Let's forget the 2PC stuff for now...Here is a scenaro:
>
> [APP/VM-1] <-> [EJB-1,EJB-2,...EJB-n/JBOSS/VM2] <-JDBC-> [DataStore-1]
>
> Each method of each of the EJBs forms a transaction by themselves if
> noone
> else issues explicit transaction control a la "begin,commit,abort".
>
> APP takes on this role. APP decides the set of EJBs' methods will form 1
> transaction. Same problem, replace APP with say a servlet running in a
> Servlet Container in a different VM and you still need the solution where
> it
> is possible to obtain a transaction from a separate VM.
>
> Sure, you could move the all the APP transaction control into one single
> method of one single EJB...but that's not always desirable, I believe...
>
> Anh
>
> ----- Original Message -----
> From: "David Jencks" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Saturday, June 16, 2001 11:34 AM
> Subject: Re: [JBoss-user] Obtaining a transaction from outside JBoss in
> another VM Plan
>
>
> > Hi,
> > I think the advice to stay away from distributed transactions is
> universal
> > design advice. Basically using distributed transactions just about
> > guarantees bad performance, as resources get tied up waiting for the
> 2pc
> to
> > make its way to all those other machines or vms not once but twice. If
> at
> > all possible, if you need things to happen on several machines, use
> > transactional messaging (jms, jbossmq) to break the work up into pieces
> > that can be all done on one machine + 1 resource manager + 1 message to
> the
> > next machine. I don't know what jboss/jbossmq actually does in this
> > scenario, however with a db and a message que as your transactional
> > resources the db (the slow part) could use 1pc:
> >
> > 1. prepare message commit
> > 2. 1pc on db
> > 3. commit message.
> >
> > This should be roughly as fast as 1pc to the db, since jbossmq is
> running
> > in the same vm as the rest of jboss.
> >
> > I learned the most about this subject from the (pre ejb) book "High
> > Performance Client Server" by Loosley and Douglas, isbn 0-471-16269-8
> >
> > david jencks
> >
> > On 2001.06.16 12:57:44 -0400 Phan Anh Tran wrote:
> > > We are at design time for a real system. Your suggestion "don't use
> it"
> > > is
> > > that due to JBOSS specific implementation issues or is it a
> universal
> > > design advice?
> > >
> > > Do you have a copy of Vlada talk? Thanks.
> > >
> > > Anh
> > >
> > > ----- Original Message -----
> > > From: "marc fleury" <[EMAIL PROTECTED]>
> > > To: <[EMAIL PROTECTED]>
> > > Sent: Saturday, June 16, 2001 3:24 AM
> > > Subject: RE: [JBoss-user] Obtaining a transaction from outside JBoss
> in
> > > another VM Plan
> > >
> > >
> > > > yes anatoly ackerman finished an integration of Tyrex (real DTM) in
> > > JBoss.
> > > >
> > > > We truly truly discourage the use of DTx (even Vlada matena had a
> full
> > > talk
> > > > on that). So my question is "are you at design time" (in which case
> > > don't
> > > > use it) or is this "real life".
> > > >
> > > > marcf
> > > >
> > > > |-----Original Message-----
> > > > |From: [EMAIL PROTECTED]
> > > > |[mailto:[EMAIL PROTECTED]]On Behalf Of Phan
> Anh
> > > > |Tran
> > > > |Sent: Saturday, June 16, 2001 3:11 AM
> > > > |To: [EMAIL PROTECTED]
> > > > |Subject: [JBoss-user] Obtaining a transaction from outside JBoss
> in
> > > > |another VM Plan
> > > > |
> > > > |
> > > > |When does JBOSS plan to support the obtaining and using a
> transaction
> > > from
> > > > |another VM? 2.2.3? 2.3? Anytime in the near future?
> > > > |
> > > > |[App/VM1] <-> [EJB1,EJB2,.../JBOSS/VM2]
> > > > |
> > > > |App needs to setup and control the transactions, so in essence, my
> > > > |App needs
> > > > |to be able to obtain a UserTransaction via JNDI from a separate
> VM.
> I
> > > > |believe this feature is not supported right now, but I would like
> to
> > > > |understand when the feature is planned to be incorporated into
> JBOSS?
> > > > |Thanks.
> > > > |
> > > > |Anh
> > > > |
> > > > |
> > > > |
> > > > |_________________________________________________________
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