On 2001.06.27 16:14:29 -0400 marc fleury wrote:
> this is an educating discussion, I never had before to think precisely of
> all the objects involved..
>
> however
>
> |I think you are agreeing with what I proposed earlier, if you have say a
> |session bean method with Requires/Serialiable calling 17 entity bean
> |methods with Requires/Read Committed, the entire transaction (started
> when
> |you get to the session bean) will be Serializable. If only one resource
>
> I am not following
>
> |manager is available, only it will be used.(one pool) This means
> different
> |methods on one bean can have different transaction isolations.
>
> what it means to me is that a transaction can be updating records with
> different isolation levels with the SAME connection to the database.
>
> I AM WRONG ON THIS ASSUMPTION? (that is ALL my discussion)
>
For most drivers, you are wrong, we'd need 2 pools and xa drivers.
> If no then 2 pools (2 types of connection IL) and 1 transaction uses 2
> connections, XA required
>
> if yes then 1 pool (2 types of connection IL) and 1 transaction uses 1
> connection, no XA required
>
> |Bill wants each entity bean to have an immutable transaction isolation
> for
>
> yes and my question is "why immutable", it is the yes and no above.
>
> |all its methods, and to be able to have several transaction isolations
> |within one transaction, using several pools connected to the same db.
> As I
> |have pointed out previously, this doesn't work the the wrapped jbosspool
> |fake xa. You get 2 indenpendent concurrent transactions, but there is
> no
> |guarantee that they will both succeed or fail. To get real
> transactions,
> |you need read xa drivers and probably to use real 2pc. ( it is
> conceivable
> |that a sophisticated driver could recognize that both resources are the
> |same, and use 1pc. THIS DOES NOT MEAN THE FAKE XA WRAPPERS WILL DO
> THIS).
>
> yes that is a problem with his multi-pool design, that you do require XA
> synchronization for using different ILs with the db (WHICH WOULD SEEM
> VERY
> NORMAL TO ME). On the other hand 1 connection does not require XA and
> 2PC,
> not that they are bad, just that they are much slower. XA is for many
> connections, we are talking about requiring many connections because of a
> claim that we cannot reset ILs within one connection.
>
> I want to make sure that the multipool design is a *requirement*, a "no
> other way" as he seems to indicate. The contention point in my mind is
> the
> simple question above
>
> can we set different ILs on a jdbc connection within one transaction
For most drivers, no. Some (informix) may, but I think there are logical
consistency problems with this.(don't have my example yet)
What I was suggesting is that possibly different methods on one (entity)
bean might want different isolations, perhaps depending on where they are
called from. I think one transaction branch <-> one isolation level is
pretty much a requirement.
However, after thinking about how this might be implemented, I think the
per-pool configuration is probably the way to go. I think there is a
design problem in the java classes: I would put the isolation as a property
of the transaction, set when the transaction is started. However, the
method to set it is on Connection, which is not enterprise-ready and
doesn't know about explicit transaction starts. Of course, putting
isolation in a global transaction would have problems of its own, such as
implying that all your resources have the same kind of isolation concepts,
and that all branches want to share isolation.... so I have no good
solution.
david jencks
>
> respect,
>
> marcf
> |
> |david jencks
> |
> |
> |>
> |> marcf
> |>
> |>
> |> |
> |> |
> |> |
> |> |_______________________________________________
> |> |Jboss-development mailing list
> |> |[EMAIL PROTECTED]
> |> |http://lists.sourceforge.net/lists/listinfo/jboss-development
> |>
> |>
> |>
> |> _______________________________________________
> |> Jboss-development mailing list
> |> [EMAIL PROTECTED]
> |> http://lists.sourceforge.net/lists/listinfo/jboss-development
> |>
> |
> |
> |_______________________________________________
> |Jboss-development mailing list
> |[EMAIL PROTECTED]
> |http://lists.sourceforge.net/lists/listinfo/jboss-development
>
>
>
> _______________________________________________
> Jboss-development mailing list
> [EMAIL PROTECTED]
> http://lists.sourceforge.net/lists/listinfo/jboss-development
>
_______________________________________________
Jboss-development mailing list
[EMAIL PROTECTED]
http://lists.sourceforge.net/lists/listinfo/jboss-development
