Monday, October 27, 2008

Introduction to Reliable Messaging with WSF/PHP

 

With WSF/PHP you can add reliability to your web services integrations . Due to the  nature of php, WSF/PHP supports only single channel reliable messaging. Single channel means you are using the same channel to transmit both the request and response.

So what is the nature of a reliable messing interaction ?

When reliable messaging is used, in addition to the actually message being transmitted , there will be handshake interactions between the client and the service to make sure that the send message is actually delivered to the service. In addition the , reliable messaging middleware handles make sure that if the receiver endpoint down, it will keep polling till the message is delivered etc.

Let see how you can implement a simple reliable messaging client using WSF/PHP.

These are the requirements.

1. You service endpoint should be able to handle single channel reliable messaging.

2.Then you need to enable addressing.

In RM, the communication happens using a sequence. The initial handshake is to build this sequence, and with a sequence , one or more application messages is transmitted. Once the messaging transmission is complete, the sequence is terminated.

So the messages exchanged in a single channel scenario is as follows. I am using the actually xml messages exchanged in the echo_client_rm.php sample that comes with WSF/PHP release here.

1. Client sending the CreateSequence Message to the service.

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsa:To>http://localhost/samples/reliable/echo_service_rm.php</wsa:To>
      <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/CreateSequence</wsa:Action>
      <wsa:ReplyTo>
         <wsa:Address>http://www.w3.org/2005/08/addressing/anonymous</wsa:Address>
      </wsa:ReplyTo>
      <wsa:MessageID>urn:uuid:6dbfe9a0-304f-415e-91d1-49d2993bcf56</wsa:MessageID>
   </soapenv:Header>
   <soapenv:Body>
      <wsrm:CreateSequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
         <wsrm:AcksTo xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
            <wsa:Address xmlns:wsa="http://www.w3.org/2005/08/addressing">http://www.w3.org/2005/08/addressing/anonymous</wsa:Address>
         </wsrm:AcksTo>
         <wsrm:Offer xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
            <wsrm:Identifier>df2ceab0-b04f-428a-bb94-0cfdcb0a524b</wsrm:Identifier>
         </wsrm:Offer>
      </wsrm:CreateSequence>
   </soapenv:Body></soapenv:Envelope>

2. Service responding with a CreateSequenceResponse message.

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsa:To>http://www.w3.org/2005/08/addressing/anonymous</wsa:To>
      <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/CreateSequenceResponse</wsa:Action>
      <wsa:From>
         <wsa:Address>http://localhost/samples/reliable/echo_service_rm.php</wsa:Address>
      </wsa:From>
      <wsa:MessageID>urn:uuid:48020317-4e90-4b79-97ae-2fa9b78c544b</wsa:MessageID>
      <wsa:RelatesTo wsa:RelationshipType="http://www.w3.org/2005/08/addressing/reply" xmlns:wsa="http://www.w3.org/2005/08/addressing">urn:uuid:6dbfe9a0-304f-415e-91d1-49d2993bcf56</wsa:RelatesTo>
   </soapenv:Header>
   <soapenv:Body>
      <wsrm:CreateSequenceResponse xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
         <wsrm:Identifier>8883a8b9-9f6a-4e40-b78a-872a2708a4b3</wsrm:Identifier>
         <wsrm:Accept xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
            <wsrm:AcksTo xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
               <wsa:Address xmlns:wsa="http://www.w3.org/2005/08/addressing">http://localhost/samples/reliable/echo_service_rm.php</wsa:Address>
            </wsrm:AcksTo>
         </wsrm:Accept>
      </wsrm:CreateSequenceResponse>
   </soapenv:Body></soapenv:Envelope>

3. Client sending the sequence Message

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsrm:Sequence soapenv:mustUnderstand="1" xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm" xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
         <wsrm:Identifier>8883a8b9-9f6a-4e40-b78a-872a2708a4b3</wsrm:Identifier>
         <wsrm:MessageNumber xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">1</wsrm:MessageNumber>
         <wsrm:LastMessage xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"/>
      </wsrm:Sequence>
      <wsa:To>http://localhost/samples/reliable/echo_service_rm.php</wsa:To>
      <wsa:Action>http://wso2.org/wsfphp/samples/echoString</wsa:Action>
      <wsa:MessageID>urn:uuid:8e275ba1-b34b-49c1-92fa-ce86782ff803</wsa:MessageID>
   </soapenv:Header>
   <soapenv:Body>
      <ns1:echoString xmlns:ns1="http://wso2.org/wsfphp/samples">       
         <text>Hello World!</text>   
      </ns1:echoString>
   </soapenv:Body></soapenv:Envelope>

4. Service Responding with a SequenceAcknowledgement message. Since this is an echo service, in addition to sending the acknowledgement, the service also initiate a sequence here and send the application message back to the client.

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsrm:Sequence soapenv:mustUnderstand="1" xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm" xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
         <wsrm:Identifier>df2ceab0-b04f-428a-bb94-0cfdcb0a524b</wsrm:Identifier>
         <wsrm:MessageNumber xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">1</wsrm:MessageNumber>
         <wsrm:LastMessage xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm"/>
      </wsrm:Sequence>
      <wsrm:SequenceAcknowledgement soapenv:mustUnderstand="0" xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm" xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
         <wsrm:Identifier>8883a8b9-9f6a-4e40-b78a-872a2708a4b3</wsrm:Identifier>
         <wsrm:AcknowledgementRange Lower="1" Upper="1"/>
      </wsrm:SequenceAcknowledgement>
      <wsa:Action>http://wso2.org/wsfphp/samples/echoString</wsa:Action>
      <wsa:ReplyTo>
         <wsa:Address>http://localhost/samples/reliable/echo_service_rm.php</wsa:Address>
      </wsa:ReplyTo>
      <wsa:From>
         <wsa:Address>http://localhost/samples/reliable/echo_service_rm.php</wsa:Address>
      </wsa:From>
      <wsa:MessageID>urn:uuid:307e881d-8ac7-4cb4-8acf-0eb04831707f</wsa:MessageID>
      <wsa:RelatesTo wsa:RelationshipType="http://www.w3.org/2005/08/addressing/reply" xmlns:wsa="http://www.w3.org/2005/08/addressing">urn:uuid:8e275ba1-b34b-49c1-92fa-ce86782ff803</wsa:RelatesTo>
   </soapenv:Header>
   <soapenv:Body>
      <ns1:echoString xmlns:ns1="http://wso2.org/wsfphp/samples">       
         <text>Hello World!</text>   
      </ns1:echoString>
   </soapenv:Body></soapenv:Envelope>

5. Client send the SequenceAcknowledgement message to the service.

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsrm:SequenceAcknowledgement soapenv:mustUnderstand="0" xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm" xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
         <wsrm:Identifier>df2ceab0-b04f-428a-bb94-0cfdcb0a524b</wsrm:Identifier>
         <wsrm:AcknowledgementRange Lower="1" Upper="1"/>
      </wsrm:SequenceAcknowledgement>
      <wsa:To>http://localhost/samples/reliable/echo_service_rm.php</wsa:To>
      <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/SequenceAcknowledgement</wsa:Action>
      <wsa:MessageID>urn:uuid:3b2b7a50-f962-4027-b240-5eea57142df1</wsa:MessageID>
   </soapenv:Header>
   <soapenv:Body/></soapenv:Envelope>

 

6. Now the service sends back a TerminateSequence Message.

<soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope">
   <soapenv:Header xmlns:wsa="http://www.w3.org/2005/08/addressing">
      <wsa:Action>http://schemas.xmlsoap.org/ws/2005/02/rm/TerminateSequence</wsa:Action>
      <wsa:MessageID>urn:uuid:6e8178c6-a566-4010-a77e-d05af67ad21a</wsa:MessageID>
   </soapenv:Header>
   <soapenv:Body>
      <wsrm:TerminateSequence xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm">
         <wsrm:Identifier>df2ceab0-b04f-428a-bb94-0cfdcb0a524b</wsrm:Identifier>
      </wsrm:TerminateSequence>
   </soapenv:Body></soapenv:Envelope>

Similarly the client and service exchanges TermianteSequenceResponse messages as well.

I am sure, now you have some understanding on what acctually happens when you try to send a soap message reliably from  one endpoint to another. In my next blog post, we will discuss how to configure WSF/PHP to implement reliable clients and services.

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