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From Amila Suriarachchi <amilasuriarach...@gmail.com>
Subject Re: WSDL generation for the services exposed only in local transport
Date Wed, 15 Jun 2011 04:28:56 GMT
hi,

There are two questions here.

1. Exposing a service only with local transport.

This is not related to synapse. Say I have two services A and B deployed in
same AxisConfiguration. I need to invoke service B from A using local
transport only.

The problem is once we deployed Service B it is exposed through all the
transports available. We can limit the exposed transports only by specifying
the transports to be exposed in the services.xml. Since there is no listner
for local transport it can not only be exposed through local transport. Then
we can add a listener for local transport to fix this. Once we add this
listener it will show the local transport end points in the WSDL as well.
This is wrong since local transport has no meaning to out side users.

I think we need to do some change in Axis2 to not to show local transport
endpoints since local transport is part of Axis2.


2. Accessing a Service through local transport which intern calls another
service using synapse nhttp transport.

Say we have three services A, B and C. Now A invoke B using local transport
and B invokes C using synapse nhttp transport.

 A -- local --> B ---- synapse nhttp --> C

This won't work with the normal local transport since synapes nhttp
transport is not blocking. As you have pointed out this nhttp transport does
not work with Any Axis2 client since it does not wait until the response
comes. Due to same reason it won't work with existing local transport as
well.

The NonBlockingLocal transport allows synapse proxy service to talk to
another web service which intern calls another service since it is not
blocking. Further synapse kernal is written not to block its wroker threads
and this transport work accordingly as well.

thanks,
Amila.


On Wed, Jun 15, 2011 at 1:27 AM, Andreas Veithen
<andreas.veithen@gmail.com>wrote:

> On Tue, Jun 14, 2011 at 08:48, Heshan Suriyaarachchi
> <heshan.suriyaarachchi@gmail.com> wrote:
> > Hi Devs,
> > I am opening up this thread to discuss $subject.
> > Recently, I did some improvements [1] to the Axis2 local transport,
> inorder
> > to get it working against Synapse nhttp transport. Now the local
> transport
> > is working fine against the nhttp transport.
>
> To me the statement "getting transport A working against transport B"
> doesn't make sense. Two distinct transports A and B never interact
> directly. Each of them interacts with the Axis2 engine through (in
> principle) well defined APIs. If a component (Synapse in this case)
> based on Axis2 has an issue when using A and B together, then either
> transport A, transport B, the component or the Axis2 engine has an
> issue (or multiple components have an issue), but saying that
> transport A needs to be fixed to work with transport B doesn't make
> sense and is an indication that the fundamental issue has not been
> identified properly.
>
> At this point, what we know is this:
> * NHTTP doesn't work as a transport sender in a standard Axis2 setup
> [1]. It only works in Synapse. That means that from the point of view
> of Axis2, the NHTTP transport is broken. That is of course OK, because
> NHTTP is shipped with Synapse and nobody claims that it is supported
> in a plain Axis2 setup.
> * At some point I tried to figure out what would need to be changed to
> make the NHTTP transport work in Axis2. IIRC the conclusion was that
> one can make it work in Axis2, but then it no longer works in Synapse.
> This would indicate that Synapse actually uses the transport API in a
> way it was not designed for.
> * As indicated in AXIS2-4944, the current version of
> NonBlockingLocalTransportSender doesn't work in Axis2. Unless somebody
> can come up with a valid unit test that exercises this piece of code,
> this would mean that we introduced a broken piece of code in Axis2 in
> order to work around another broken piece of code in a downstream
> project. That is of course not OK.
>
> Note that the issue with NonBlockingLocalTransportSender is also
> blocking the review of other issues such as AXIS2-4991, because it is
> not possible to construct a unit test that validates (or invalidates)
> the proposed patch. That is BTW a general issue with the recent
> patches for the local transport. As far as I can tell, none of them
> added any new unit tests.
>
> [1] At least that was my conclusion when I last looked at it. I'm
> ready to retract that claim if somebody comes up with an example that
> shows how to set up a simple Axis2 client that uses NHTTP as outgoing
> transport.
>
> > Now, my requirement is to expose an Synapse Proxy Service only in local
> > transport. The reason behind is that, these proxy services which are
> exposed
> > only in local transport will be used by other proxy services and will not
> be
> > available for outside parties. Earlier, axis2 local transport did not
> have a
> > TransportListener.
> > With a TransportListener
> > ====================
> > I introduced [2] a TransportListener to the local transport. The
> transport
> > listener's methods are used to calculate the endpoints for the service
> which
> > will be used in generating the WSDL for the service. Therefore, now if
> the
> > service exposed in the local transport, the local endpoint is also shown
> in
> > the WSDL. Although the local endpoints are shown in the WSDL, outside
> > parties can not access the local endpoint.
> > The problem this patch introduce is, now the WSDL shows the local
> transport
> > endpoints. Which is wrong since external users can not access local
> > transport.
> > So the solution is not to show the local transport endpoints in generated
> > wsdl. For that we may have to change Axis2 code.
> > eg: As an example, I am attaching the following resources to prove my
> point.
> > The synapse-config.xml is the Synapse Configuration and the attached
> WSDLs
> > are for the proxy servivces, LocalTransportProxy and SecondProxy. The
> > SecondProxy is exposed only via the local transport and the local
> endpoints
> > are shown in the WSDL which is wrong IMV.
> > Without a TransportListener
> > ======================
> > If we did not have a LocalTransportListener and if a service is exposed
> > through local transport only, the WSDL for the service will not be
> > generated. The reason behind is that; inorder to generate the WSDL, there
> > should be a mechanism to derive the endpoints for the service. Since, the
> > TransportListener is not there, there is no mechanism to derive the
> > endpoints for the service(which is only exposed through the local
> > transport).
> > In case the service exposed through http,https,local transports; this
> wont
> > be the case. Then the WSDL will be generated and only the http,https
> > endpoints will be shown.
> > Without the listener, if we expose a service only in local transport,
> WSDL
> > generation fails since the endpoints can not be derived for that
> particular
> > service.
> >
> > Your ideas and feedback on $subject is much appreciated.
> > [1] - https://issues.apache.org/jira/browse/AXIS2-4944
> > [2] - https://issues.apache.org/jira/browse/AXIS2-5043
> >
> >
> > --
> > Regards,
> > Heshan Suriyaarachchi
> >
> > http://heshans.blogspot.com/
> >
> >
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> >
>
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>


-- 
Amila Suriarachchi
WSO2 Inc.
blog: http://amilachinthaka.blogspot.com/

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