This documentation is for WSO2 ESB version 4.0.2. View documentation for the latest release.

Sample 1 Message Exchange between ESB and Server

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Last updated: Dec 13, 2011Version comment
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Objective: Demonstrate the message exchange between ESB and the back-end server using WS-ReliableMessaging (WS-RM).

Prerequisites
  • Deploy the ReliableStockQuoteService in the sample Axis2 server by switching to the samples/axis2Server/src/ReliableStockQuoteService directory and running ant.
  • Start the sample Axis2 server on port 9000.
  • Start ESB with the sample configuration 101: wso2esb-samples -sn 101.
<definitions xmlns="http://ws.apache.org/ns/synapse">

    <in>
        <RMSequence single="true" version="1.0"/>
        <send>
           <endpoint name="reliable">
              <address uri="http://localhost:9000/services/ReliableStockQuoteService">
                 <enableRM/>
                 <enableAddressing/>
              </address>
           </endpoint>
        </send>
    </in>
    <out>
        <header name="wsrm:SequenceAcknowledgement" action="remove"
                xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"/>
        <header name="wsrm:Sequence" action="remove"
                xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"/>
        <header name="wsrm:AckRequested" action="remove"
                xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"/>
        <send/>
    </out>

</definitions>

In the above configuration, WS-RM is engaged to the endpoint using the <enableRM/> element. It is possible to engage WS-RM to both Address and WSDL endpoints using this element. In addition to the RM enabled endpoint, RMSequence Mediator is specified before the Send Mediator. This mediator is used to specify the set of messages to be sent using a single RM sequence. In this sample, it is specified as single message per sequence. It also specifies the version of the WS-RM to be used. RM related SOAP headers are removed from the message in the Out Mediator as WS-RM message exchange happens only between the ESB and the server. Run the sample client using the following command.

ant stockquote -Dsymbol=IBM -Dmode=quote -Daddurl=http://localhost:8280

You can observe the client output displaying the quote price for IBM as follows:

[java] Standard :: Stock price = $189.2521262517493

There is no difference to be observed between the normal message exchange and WS-RM enabled message exchange as far as client and server outputs are considered. But if you look at the wire level messages, you would observe additional WS-RM messages and WS-RM elements. ESB, the initiator of the RM sequence, first try to create a sequence by sending a message with CreateSequence element.

...
<soapenv:Body>
   <wsrm:CreateSequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
      <wsrm:AcksTo>
         <wsa:Address>http://www.w3.org/2005/08/addressing/anonymous</wsa:Address>
      </wsrm:AcksTo>
      <wsrm:Offer>
         <wsrm:Identifier>urn:uuid:546F6F33FB7D8BBE351179807372769</wsrm:Identifier>
      </wsrm:Offer>
   </wsrm:CreateSequence>
</soapenv:Body>
...

Sample Axis2 server responds to CreateSequence request with the following message:

...
<soapenv:Body>
   <wsrm:CreateSequenceResponse xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
      <wsrm:Identifier>urn:uuid:879853A6871A66641C1179807373270</wsrm:Identifier>
      <wsrm:Accept>
         <wsrm:AcksTo>
            <wsa:Address>http://localhost:9000/services/ReliableStockQuoteService</wsa:Address>
         </wsrm:AcksTo>
      </wsrm:Accept>
   </wsrm:CreateSequenceResponse>
</soapenv:Body>
...

Once the sequence is established, ESB sends the request to the server with the prenegotiated sequence ID.

<soapenv:Envelope xmlns:wsa="http://www.w3.org/2005/08/addressing"
                  xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
    <soapenv:Header>
        <wsa:To>http://localhost:9000/services/ReliableStockQuoteService</wsa:To>
        <wsa:MessageID>urn:uuid:DB9A5257B637DDA38B1179807372560712002-1515891720</wsa:MessageID>
        <wsa:Action>urn:getQuote</wsa:Action>
        <wsrm:Sequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"
                       soapenv:mustUnderstand="1">
            <wsrm:Identifier>urn:uuid:879853A6871A66641C1179807373270</wsrm:Identifier>
            <wsrm:MessageNumber>1</wsrm:MessageNumber>
            <wsrm:LastMessage/>
        </wsrm:Sequence>
    </soapenv:Header>
    <soapenv:Body>
        <m0:getQuote xmlns:m0="http://services.samples/xsd">
            <m0:request>
                <m0:symbol>IBM</m0:symbol>
            </m0:request>
        </m0:getQuote>
    </soapenv:Body>
</soapenv:Envelope>

ESB keeps on sending above message till the server responds with a valid response message with "200 OK" HTTP header. If the server is not ready with a response, it will respond with "202 Accepted" HTTP header for all requests. Once the server is ready with a response, it will send the response message with sequence ID as follows.

<soapenv:Envelope xmlns:wsa="http://www.w3.org/2005/08/addressing"
                  xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
    <soapenv:Header>
        <wsa:MessageID>urn:uuid:879853A6871A66641C1179807373804</wsa:MessageID>
        <wsa:Action>http://services.samples/ReliableStockQuoteServicePortType/getQuoteResponse
        </wsa:Action>
        <wsa:RelatesTo>urn:uuid:DB9A5257B637DDA38B1179807372560712002-1515891720</wsa:RelatesTo>
        <wsrm:Sequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"
                       soapenv:mustUnderstand="1">
            <wsrm:Identifier>urn:uuid:546F6F33FB7D8BBE351179807372769</wsrm:Identifier>
            <wsrm:MessageNumber>1</wsrm:MessageNumber>
            <wsrm:LastMessage/>
        </wsrm:Sequence>
        <wsrm:SequenceAcknowledgement xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"
                                      soapenv:mustUnderstand="1">
            <wsrm:Identifier>urn:uuid:879853A6871A66641C1179807373270</wsrm:Identifier>
            <wsrm:AcknowledgementRange Lower="1" Upper="1"/>
        </wsrm:SequenceAcknowledgement>
    </soapenv:Header>
    <soapenv:Body>
        <ns:getQuoteResponse xmlns:ns="http://services.samples/xsd">

Now both ESB and the server are done with the actual message exchange. Then ESB sends a request to terminate the sequence as follows:

<soapenv:Envelope xmlns:wsa="http://www.w3.org/2005/08/addressing"
                  xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
    <soapenv:Header>
        <wsa:To>http://localhost:9000/services/ReliableStockQuoteService</wsa:To>
        <wsa:MessageID>urn:uuid:546F6F33FB7D8BBE351179807379591</wsa:MessageID>
        <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/TerminateSequence</wsa:Action>
        <wsrm:SequenceAcknowledgement xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"
                                      soapenv:mustUnderstand="1">
            <wsrm:Identifier>urn:uuid:546F6F33FB7D8BBE351179807372769</wsrm:Identifier>
            <wsrm:AcknowledgementRange Lower="1" Upper="1"/>
        </wsrm:SequenceAcknowledgement>
    </soapenv:Header>
    <soapenv:Body>
        <wsrm:TerminateSequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
            <wsrm:Identifier>urn:uuid:879853A6871A66641C1179807373270</wsrm:Identifier>
        </wsrm:TerminateSequence>
    </soapenv:Body>
</soapenv:Envelope>

Server responds to the sequence termination message, accepting to terminate the sequence as follows:

<soapenv:Envelope xmlns:wsa="http://www.w3.org/2005/08/addressing"
                  xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
    <soapenv:Header>
        <wsa:ReplyTo>
            <wsa:Address>http://localhost:9000/services/ReliableStockQuoteService</wsa:Address>
        </wsa:ReplyTo>
        <wsa:MessageID>urn:uuid:879853A6871A66641C1179807380190</wsa:MessageID>
        <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/TerminateSequence</wsa:Action>
    </soapenv:Header>
    <soapenv:Body>
        <wsrm:TerminateSequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
            <wsrm:Identifier>urn:uuid:546F6F33FB7D8BBE351179807372769</wsrm:Identifier>
        </wsrm:TerminateSequence>
    </soapenv:Body>
</soapenv:Envelope>

Note

Although each of above messages are separate SOAP messages, in most cases they will be exchanged in a single socket connection as HTTP "Keep-Alive" header is used.