SPAM Re: ServiceMix integration

[Guillaume Nodet]

Thanks Dain.

As Aaron just pointed in its previous mail, the component may have its 
own JNDI context, but Service Units may need some too.  And the problem 
is that a service unit may not contain any code, just some data: the 
components will handle the data and perform the necessary tasks.  So the 
use of JNDI references can only work for components, not for service units.

I really think that a global JNDI context would be the most appropriate 
thing, though the problem is to determine which resources will be in it 
i guess. 
I had in mind to create a context and binding resources dynamically with 
a gbean query by querying JCAManagedConnectionFactory with 
J2EEApplication=null.  I have looked at the code for geronimo-naming  
and related context creation upon deployment, and I do not really see 
how resources can be bind in a JNDI context without knowing their main 
interface.  This information is provided when referencing such a 
resource from a web-app deployment descriptor, but in my case, I do not 
have such information.  If you have any hints on that it would be cool ...

Cheers,
Guillaume Nodet


Dain Sundstrom wrote:

It appears that the JBI spec didn't provide any way to normalize the  
JNDI environment between different app servers (JBI 1.0 page 241):

getNamingContext()
  public javax.naming.InitialContext getNamingContext()
  Get the JNDI naming context for this component. This context is a  
standard JNDI InitialContext but
  its content will vary based based on the environment in which the  
JBI implementation is running.
  Returns: the JNDI naming context; must be non-null.

Rather than try to shoehorn ServiceMix into a Geronimo paradigm,  
Guillaume how do you want this to work in Geronimo?

Based on the number of requests for a global JNDI, I think we need to  
finally implement it regardless of how distasteful some may find it.   
Of course, I'd schedule it for Geronimo 1.2 :)

-dain

On Apr 4, 2006, at 9:46 AM, Aaron Mulder wrote:

I guess I'm wondering how this will work with other app servers, and
how portable the code will be.  Let's say you're trying to deploy the
same EJB+JBI configuration in ServiceMix+Geronimo and also
ServiceMix+App Server X where that product supports a global JNDI
space.

Will the code look like this?

SomeEJBHome home = null;
if(amIinGeronimo()) {
    // Geronimo uses local JNDI space with mapping file
    home = new InitialContext().lookup("java:comp/env/ejb/SomeEJB");
} else if(amIinAppServerX()) {
    // App Server X uses global JNDI space
    home = new InitialContext().lookup("ejb/SomeEJB");
} else ...

Or would you plan to have geronimo-jbi.xml and also appserverx-jbi.xml
so that the code could be the same for both
("java:comp/env/ejb/SomeEJB") and it would just be the mapping
strategy that was different depending on which product you were
deploying in?

I think it would be "more portable" to have the code always use the
local JNDI space and assume that each app server will have their own
way to write a mapping file (product-jbi.xml or whatever) to force
something into a local JNDI space accessible to the JBI components.
This way the code wouldn't be different for different servers, only
the config files.  However, 1) that requires you always write a
mapping file and 2) we have no proof that any other app server would
allow a local JNDI space for JBI components...

It seems like a bit of a dilemma.  I'm comfortable going with a
geronimo-jbi.xml strategy if you are.

If we wanted to minimize mapping requirements, we could try to do
something like map all EJBs in the same EAR into the local JNDI space
of the JBI component by default, though the auto-generated names might
be a bit ugly (java:comp/env/name-of-ejb-jar-in-ear/name-of-ejb-in- 
ejb-jar).
 Then you'd only need to provide manual mapping for any EJBs in a
different EAR.  I'm not sure how easy this would be to implement (in
particular, I think it would be hard if we couldn't force the EJB
deployer to run before the JBI deployer), but we might as well think
about what we'd like to see and then we can figure out how easy it is
to do it.  :)


Another related question I have is, will you be able to deploy both
JBI components (containers, such as a BPEL engine) and also JBI
service units (things to deploy into those JBI components, such as a
specific BPEL process) using the Geronimo deployer infrastructure?  I
think I understand deploying Service Units (in a Service Assembly zip)
but I don't understand what a JBI component deployment looks like
(other than it's a JAR).  Will both of these require resource mapping,
or will it only be the service units that need specific resources?
That is, will it be the case that you give the BPEL Engine a database
to save its state to for all its processes, or will you only give each
BPEL Business Process a database that the engine should save its state
to?

Thanks,
    Aaron

P.S. I'd also like to have a way to automatically connect Session EJBs
to the JBI bus if they define a WSDL interface.  But this is a
different issue.  :)

On 4/4/06, Guillaume Nodet <[EMAIL PROTECTED]> wrote:

Thanks Aaron, see comments inline...

Aaron Mulder wrote:

Guillaume,

You're right that there's generally no server-wide JNDI context.   
It's
possible to look up any resource in the server at runtime using
Geronimo-specific APIs (such as Kernel.listGBeans, or using the  
JSR-77
management APIs).  For J2EE apps, the standard practice leans  towards
binding everything at deployment time, so we have a deployment
descriptor that maps the declared resources to actual resources  in 
the
server during deployment.  Then we create the component-specific  JNDI
space during deployment containing the resources to be made  avaliable
to the component, because that's what J2EE dictates.  But it's  not 
the
only possible way things could work.


Thanks for these precisions.  It confirms what i was thinking by  
looking
at the code.

I'm having trouble wrapping my head around how resources should
normally work in ServiceMix.  Is there some place in jbi.xml or  other
standard JBI deployment information for, say, a service unit to
declare that it needs resources like a JMS connection factory and
destination?  If not, how is ServiceMix/Geronimo supposed to know  
what
resources to provide?  Is there just an assumption that a global  JNDI
namespace will be present containing every resource in the server  and
each component can look up whatever it wants to?


The only relationship between JBI and JNDI is that the JBI container
should provide an InitialContext for a JBI component.
See
http://java.sun.com/integration/1.0/docs/sdk/api/javax/jbi/ 
component/ComponentContext.html
In addition to the JNDI context, a MBeanServer and a  
TransactionManager
should be provided.  These are really the only links between JBI  
and J2EE.
However, the purpose of JBI is to integrate things, so I guess  
accessing
JMS resources, EJBs or JDBC datasources ia a must.
Let's take a real example: the BPE BPEL engine (in incubating ODE  
apache
project) uses EJB as a persistence mechanism (the current JBI  
component
for BPE only uses memory persistence), so the BPEL engine itself  
has to
be deployed in Geronimo.  Then the JBI component would need to lookup
and call these EJB to actually perform the work.

The questions you are asking are really the ones for which i look
answers.  I have no real idea what is the best way.  The only thing I
know is that the JBI spec does not define anything on that.  I was
thinking of creating a geronimo-jbi.xml deployment plan where JNDI
resources would be specified and where gbeans could be added.  I  guess
this is the only solution to work around the problem that there is no
global JNDI context.

In addition, if we take the ODE-BPE engine, I think that the EJB  
jar and
the JBI component could be deployed inside the same EAR.  This means
that the J2EE deployer should be enhanced to support JBI modules.
Obviously, this is not supported by the J2EE specs, and as djencks  
said,
this need to be tuned off if needed.
(Though if the JBI container configuration is stopped, I think  this 
will
be automatic).

I 'm really looking for feedback on this as I am not not a J2EE  
expert,
nor a Geronimo expert ...

Cheers,
Guillaume Nodet

Thanks,
   Aaron

On 4/4/06, Guillaume Nodet <[EMAIL PROTECTED]> wrote:


Thanks to dain and djencks advises, I have began to write a real
ServiceMix integration for Geronimo.
However I am facing a number of problems.

The problem is that the JBI spec needs some things to be done when
undeploying jbi artifacts so I will be in need of an event fired  
before
undeployment (and not after as this is the current case).  Let me
explain the use case for this.
The JBI container is a server (like a web server or EJB server): it
accepts three kind of deployment artifacts: component, shared  
libraries
and service assemblies.  A shared library is a collection of  jars 
to be
added to the classpath of a component.  A component is also a  
container,
like a BPEL engine for example.  A service assembly is a package
containing service units.  These service units are given to a  target
component upon deployment.  A service unit could a BPEL process.
When deploying a BPEL process onto a BPEL engine, the engine may  
have to
store the process in a database at deployment time and remove  the 
clean
the database when undeploying the service unit.  The JBI spec  has 
all
the needed interfaces to perform these deployment / undeployment  
steps.
The only problem is that I have not found any way to know when a
configuration is being undeployed.
Looking at the kernel, it seems it should be quite easy to do, so I
think I will raise a JIRA for that and attach a patch at a later  
time.

The next problem, which is IMHO more important, is how to access  
managed
resources.  In the previous BPEL engine example, the component  
has to
access a database.  A JMS component would access a JMS connection
factory.  These resources should be accessed via JNDI.  I have  
browsed
the naming / deployer code these past days and AFAIK, there is no
server-wide JNDI context.  When a web app is deployed, a  specific 
JNDI
context is created (and bound to the thread with interceptors),  that
includes all the bindings referenced in the web deployment  
descriptor.
This leads me to think that I have to create a geronimo-jbi.xml
deployment descriptor which will contain resource references  and 
/ or
additional gbeans for the configuration.
I fear this will lead to another problem, which is the fact that  
these
resources are usually deployed inside an EAR and JBI artifacts  
can not...
So the main questions is: did I miss something ? Is there any  
easier way
to access server-wide resources or do I really have to create a  
specific
deployment plan of some kind ?

Cheers,
Guillaume Nodet