Ok,
I read a lot of confusion here, and I am very confused.
Short answer, it belongs in jboss.xml.
However first things first. We do not implement transaction isolation
settings on the database connections we get (do we?). I want to understand
how to implement it.
Re: Transaction isolation level. It is a JDBC only call and we set it once
on the connection. The database isolates the *records* that are accessed by
the application server by enrolling these in the transaction that is running
and releasing the records when the transaction is done.
It is then my understanding that when a driver enrolls a resource it must do
so through the XA protocols and I am fuzzy as to who registers the XA
resource in the ongoing transaction. Do the minerva pools make sure that if
there is a JBoss transaction then we register a listener?
Do the connectors provide a unified way to do this, how do they map to say a
Oracle driver or a postgreSQL driver.
Another question I have is the following: what is the default isolation
level set on databases with JDBC? I would imagine that since there is very
little usage of JTS infrastructure that there is *very* spotty support for
the stuff I described... jdbc is such a mess.
Simply speaking, we can define the transaction isolation tag in jboss.xml
that is the easy part, what we do with it is still a bit of a mistery... I
am not surprised that Mad Andy couldn't get it to work in WebLogic.
|> Does anyone have opinions on whether this would be a good feature or
|> not? The 1.1 spec does not specify how isolation levels should be
|> handled, except for BMT session beans, and by saying/implying that beans
|> can call resource manager specific APIs to set it themselves (carefully).
sure, still how does the driver listen for the JBoss demarcation, if someone
can explain that clearly to me it would be great. But to answer your
question directly, I would say that *possibly* CMT/CMP is the only one where
we *need* to specify the isolation level.
|What do mean by "cover BMP and CMP entities as well as sessions"? This
|can only apply to JDBC connections, right? Do you propose to set the
Yes,
|isolation level when a connection handle is obtained by the bean? If
In case of CMP/BMP whenever we obtain a connection we need to set the
isolation levels on it. We would need to put these calls in the CMP code
for jaws and we can set it ourselves (explicit call). In the case of BMP it
is a bit more complicated as the only indirection that we have is that one
that comes out of the naming and the one in the pools which are today
minerva. We would need to either find the wrapper JCA approach to do it
with JBoss or pass jboss.xml information to minerva. Again, in both cases,
I am interested in hearing clearly how this is implemented by the driver
vendors (does postgresSQL support this for example)
Also I find myself wondering if a BMP call should not be set by the bean
directly... i.e. let's NOT go through 1000 lines of code to save the bean
developer **1** line.
|so, this should probably be implemented using the same mechanism I have
|in mind to implement beans hanging onto connection handles across
|transactions.
|
|JBossCX defines the JBossConnectionListener interface for this purpose,
|although it is not currently used. The idea is that when a resource
|adapter gives out a connection handle, the app server is notified so
|that it can make sure it is participating in the correct transaction.
|It would be easy to extend that to any transaction-specific setup we
|wanted to do.
Ok so in that indirected code the appserver is notified of the fact the
connection was handed out and I assume that the connection object is passed
to the container. You would have to cast that connection to a "JDBC"
connection and set the isolation levels on it. The locking is clearly an
application level issue (lock these records like this) since the same
connection can access different records we set the isolation at the
container level ** with app knowledge** and that is controlled by JBoss.
In case of CMP we can set the transaction isolation levels in the jaws code,
we are in the body of the container code (CMP) and we can take a look at the
isolation levels passed by the jboss.xml.
In case we are BMP... it becomes really complex since the bodies of code
where we can indirect (the naming and the container notification you show in
JCA) have **no** knowledge of the application flow (or does JCA know?)... in
ANY case, I would argue that in case of ***BMP*** we SHOULD'NT set anything
ourselves and if I remember the spec correctly (but these memories get
fuzzy) we must NOT set anything in BMP... the user does it ... one freaking
line in his body of code.
CMP' case is trivial. We just go in the JAWS code where we "get" the
connection and we set the isolation level (everytime?) on it. Again I would
really appreciate someone explaining clearly to me the "under the hood" of
how a driver listens for JBoss demarcations (the association of the thread
is JBoss only, how can Oracle know that we are running in front of them.. I
JUST DON'T SEE THAT!!!!!!! can JCA help there at ALL?). But again it would
be TRIVIAL to implement the CMP case (2 lines of code). The BMP case I
argue that we don't have to do ANYTHING. The CMT/BMT cases are irrelevant.
marc
|
|Toby.
marc
|
|
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