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From "ant elder (JIRA)" <...@tuscany.apache.org>
Subject [jira] Commented: (TUSCANY-2445) [Proposal] Support of conversational web service
Date Tue, 01 Jul 2008 09:19:45 GMT

    [ https://issues.apache.org/jira/browse/TUSCANY-2445?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609501#action_12609501

ant elder commented on TUSCANY-2445:

This looks like a great addition to me, its useful new function , well written, and doesn't
break any existing functionality. Is there any reason to not apply the patch now and iteratively
work on the improvements being discussed? (I'll apply it soon unless anyone shouts) 

Yang, I'm not sure what to do with the HelloWorldConversational.zip what do you think about
making a new itest out of it so it can be run as part of the build, would you submit another
patch for that?

> [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",
>             OMElement identifierHeader = sequenceHeader.getFirstChildWithName(new QName("http://schemas.xmlsoap.org/ws/2005/02/rm",
>             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.

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