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From "Simon Laws" <simonsl...@googlemail.com>
Subject Re: [jira] Commented: (TUSCANY-2445) [Proposal] Support of conversational web service
Date Tue, 01 Jul 2008 09:03:32 GMT
On Mon, Jun 30, 2008 at 6:31 PM, Raymond Feng (JIRA) <dev@tuscany.apache.org>
wrote:

>
>    [
> https://issues.apache.org/jira/browse/TUSCANY-2445?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609297#action_12609297]
>
> Raymond Feng commented on TUSCANY-2445:
> ---------------------------------------
>
> Thanks Yang for the contribution!
>
> A few comments on top of Simon's:
>
> 1. The parsing part is done by Luciano and the changes are in the code base
> already.
>
> 2. AS we can support the exchange of the conversation states using
> different protocols such as WS-Addressing and WS-RM, we probably need to
> define an extension point here to allow the pluggability.
>
> > [Proposal] Support of conversational web service
> > ------------------------------------------------
> >
> >                 Key: TUSCANY-2445
> >                 URL: https://issues.apache.org/jira/browse/TUSCANY-2445
> >             Project: Tuscany
> >          Issue Type: Improvement
> >            Reporter: Yang Sun
> >            Priority: Minor
> >         Attachments: HelloWorldConversational.zip, rm-patch.patch
> >
> >   Original Estimate: 168h
> >  Remaining Estimate: 168h
> >
> > I want to improve Tuscany by supporting the conversational behavior in
> web service client side binding. The following is my proposal and I also
> have a prototype to demonstrate my idea. Please give me some feedback.
> > Improvement Background:
> > -----------------------------------
> > Sometimes, the client wants to keep some session-like variables between
> the calls to the server. Eg,
> >   1. Login to the server side by providing the security credential;
> >   2. Get the invoice data from the Tuscany domain by web service;
> >   3. Update the invoice data by calling Tuscany web service interface;
> >   4. Do other business related tasks;
> >   5. Logoff from the server side.
> > Currently, Tuscany web service don't support this kind of conversational
> feature.
> > SCA Related Spec:
> > --------------------------
> > In SCA assembly spec, it clarifies the external behavior of
> conversational service and the use of wsdl to declare the conversational
> behavior of its binding web service.
> > To support the conversational feature, the WSDL should support the
> declaration of the following attributes:
> >   1. sca:requires=conversational -- Declares at the porttype level to
> make the functions in port type conversational.
> >   2. sca:endConversation=true/false -- Declares at the function level to
> give the function a special meaning (end the conversation).
> > And the spec said SCA should use webservice reliable messaging as the
> communication protocol.
> > My Proposal:
> > ------------------
> > Fortunately, Luciano provides a new parser mechanism which support the
> parsing of sca:requires and sca:endConversation and etc. So the things left
> me to do is simple (if I am not wrong). I list my major changes.
> >   1. Integrating Axis addressing and sandesha2 modules to the
> packages.(Sandesha module implements ws-rm and ws-rm relys on addressing, so
> we need addressing module as well) -- by copying addressing-1.3.mar,
> sandesha2-1.3.mar to
> \src\main\resources\org\apache\tuscany\sca\binding\ws\axis2\engine\config in
> tuscany-binding-ws-axis2 module;
> >   2. Engaging addressing and sandesha2 modules if the port type is
> conversational. -- Modifications to TuscanyAxisConfigurator;
> >   3. Extract the identifier header in SOAP header and make it as the
> conversationID. A code snippet in my prototype is as below. (in
> Axis2ServiceProvider.invokeTarget() method).
> >             if (isConversational()) {
> >               SOAPHeader soapHeader = inMC.getEnvelope().getHeader();
> >               Iterator<OMElement>headerIterator =
>  soapHeader.getChildren();
> >               while (headerIterator.hasNext()) {
> >                 OMElement currentEle= headerIterator.next();
> >               }
> >
> >             OMElement sequenceHeader =
> soapHeader.getFirstChildWithName(new QName("
> http://schemas.xmlsoap.org/ws/2005/02/rm", "Sequence"));
> >             OMElement identifierHeader =
> sequenceHeader.getFirstChildWithName(new QName("
> http://schemas.xmlsoap.org/ws/2005/02/rm", "Identifier"));
> >             conversationID = identifierHeader.getText();
> >           }
> > After the changes, the basic functions of conversational web service
> works.
> > Test for the prototype:
> > -----------------------------
> > 1. I wrote a demo client to check the working of conversational web
> service. It is a enhancement to a echo string. (attach the files as well)
> >     It can trace the calls to the service from a WS-RM client and give
> different feedbacks based on the call frequencies.
> >     It also supports the method which marked as endConversational.
> > 2. Run all the test cases in tuscany-binding-ws-axis2.
> > Qustions need to be discussed:
> > -------------------------------------------
> > I have a confusion on the handling of endConversation in the prototype
> and I have some thoughts on its implementation. But I am not sure whether I
> am on the right track.
> > In the prototype, I have not made any further processing. But I am
> thinking I can make some improvements here to better support the
> conversational. Pls help me review it. The following is my idea.
> > As we know, we can achieve endConversation effect in two ways:
> >   1. end the underlying WS-RM conversation -- by sending endSequence
> command
> >   2. end the conversation at the Tuscany side by calling the method
> marked as endConversation
> > For the situation 1, if I don't do anything, the external behavior is
> correct since the identifier is re-created after the conversation end and
> the conversation manager will use the new conversationId to get the
> conversation variables. But it will left the variables for the ended
> conversation in the ConversationManager. It is a memory leak till the
> timeout of ConversationManager. And it will affect the scalability of SCA
> domains.
> > My improvement idea: write a axis handler at RMPhase and listen to
> endConversation command. If we got that command, the handler will find the
> ConversationManager and call its method to clear the variables according to
> its ending identifier.
> > For the situation 2, if I don't do anything, the behavior can still be
> right. But we must have a constraint here: the corresponding java interface
> must marked with @endConversation. If not, the conversation sequence will be
> lost (from CONVERSATION_END to CONVERSATON_CONTINUE) and the conversation
> cannot be ended.
> > My improvement idea: from my understanding, the invocation source should
> decide the conversation sequence. So whether or not the invocation target
> marked with endConversation, the conversation sequence should be
> CONVERSATION_END if the invocation source is marked as CONVERSATION_END. A
> quick fix here is to copy the conversation  sequence from the invocation
> source to invocation target when tuscany looks up the InvocationChain. Or at
> least, we should make some check at the interface compatible logic and give
> the user a warning message when the conversation sequence is not compatible.
> > Thanks for reading so long and pls provide me your feedback.
> >
>
> --
> This message is automatically generated by JIRA.
> -
> You can reply to this email to add a comment to the issue online.
>
>
I also have a question about the conversation end processing and fix that is
described.Are you suggesting that we should deal with cases where the
reference and service are marked inconsistently with respect to
conversational annotations? Looking at the interface contract mapper code it
doesn't look like we check  conversational annotations for compatibility. I
agree that the least we should do is raise a warning in this case. I
wouldn't go as far as saying that we need to copy annotations from reference
to service though.

Simon

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