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From Simon Nash <n...@apache.org>
Subject Re: [jira] Commented: (TUSCANY-2445) [Proposal] Support of conversational web service
Date Tue, 01 Jul 2008 11:33:24 GMT
ant elder (JIRA) wrote:
>     [ 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) 
How does the patch decide whether to call WS-RM or use the existing
WS-Addressing support for conversational calls over Web services?
I looked at the code, but I couldn't see where this was being done.


> 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
>> 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", "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.

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