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Point-to-Point Channel

This page explains how you can implement a sample scenario of Point-to-Point Channel EIP using WSO2 Micro Integrator.

Introduction to Point-to-Point Channel

The Point-to-Point Channel EIP allows only a single receiver to consume a sent message when multiple receivers are waiting to consume it.

Info

For more information, go to Point-to-Point Channel.

Sample scenario

The sample scenario is an inventory for stocks. It illustrates how a stock quote is generated, which only a single consumer receives at a given time. The diagram below depicts how to simulate the sample scenario.

Point-to-Point Channel

Synapse configurations of the artifacts

When you unzip the ZIP file you downloaded below in step 9 when simulating the sample scenario, you can find the below configurations in the <UNZIPPED_FILE>/src/main/wso2mi/artifacts directory. For more information about these artifacts, go to Develop Integration Solutions Documentation.

<?xml version="1.0" encoding="UTF-8"?>
<proxy name="PointToPointProxy" startOnLoad="true" transports="http https" xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <call>
                <endpoint key="LoadBalanceEp"/>
            </call>
            <respond/>
        </inSequence>
        <faultSequence/>
    </target>
</proxy>

<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="LoadBalanceEp" xmlns="http://ws.apache.org/ns/synapse">
    <loadbalance algorithm="org.apache.synapse.endpoints.algorithms.RoundRobin">
        <endpoint key="SimpleStockEp1"/>
        <endpoint key="SimpleStockEp2"/>
        <endpoint key="SimpleStockEp3"/>
    </loadbalance>
    <description></description>
</endpoint>

<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="SimpleStockEp1" xmlns="http://ws.apache.org/ns/synapse">
    <address uri="http://localhost:9001/services/SimpleStockQuoteService/">
        <suspendOnFailure>
            <initialDuration>-1</initialDuration>
            <progressionFactor>1</progressionFactor>
        </suspendOnFailure>
        <markForSuspension>
            <retriesBeforeSuspension>0</retriesBeforeSuspension>
        </markForSuspension>
    </address>
</endpoint>

<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="SimpleStockEp2" xmlns="http://ws.apache.org/ns/synapse">
    <address uri="http://localhost:9002/services/SimpleStockQuoteService/">
        <suspendOnFailure>
            <initialDuration>-1</initialDuration>
            <progressionFactor>1</progressionFactor>
        </suspendOnFailure>
        <markForSuspension>
            <retriesBeforeSuspension>0</retriesBeforeSuspension>
        </markForSuspension>
    </address>
</endpoint>

<?xml version="1.0" encoding="UTF-8"?>
<endpoint name="SimpleStockEp3" xmlns="http://ws.apache.org/ns/synapse">
    <address uri="http://localhost:9003/services/SimpleStockQuoteService/">
        <suspendOnFailure>
            <initialDuration>-1</initialDuration>
            <progressionFactor>1</progressionFactor>
        </suspendOnFailure>
        <markForSuspension>
            <retriesBeforeSuspension>0</retriesBeforeSuspension>
        </markForSuspension>
    </address>
</endpoint>

Set up the sample scenario

Follow the below instructions to simulate this sample scenario.

  1. Install WSO2 Micro Integrator.

    Info

    Follow the Install the Micro Integrator Runtime documentation for more information.

  2. Launch Visual Studio Code with the Micro Integrator for VS Code extension (MI for VS Code) installed.

    Info

    Follow the Install Micro Integrator for VS Code documentation for a complete installation guide.

  3. Download the backend service.

  4. Extract the downloaded zip file.

  5. Open a terminal, and navigate to the axis2Server/bin/ directory inside the extracted folder.

  6. Execute the following command to start the axis2server with the SimpleStockQuote backend service:

    sh axis2server.sh

    axis2server.bat

  7. Navigate to the MI_HOME/bin/ directory and start the tcpmon application.

    For instructions, go to Starting TCPMon Documentation.

  8. In the tcpmon application, navigate to the Admin tab. Add listeners to ports 9001, 9002, and 9003. For each listener set the target hostname to localhost and target port to 9000 in each instance.

  9. Download the artifacts of the sample.

    Download ZIP

  10. Import the artifacts to WSO2 MI.

    Click File -> Open Folder -> Select the extracted ZIP file to import the downloaded ZIP file.

  11. Start the project in the WSO2 MI server.

    For instructions, go to Build and Run Documentation.

Execute the sample

Send the following request 3 or more times. Make sure to include a simpleClientSession in the header.

POST http://localhost:8290/services/PointToPointProxy
Content-Type: text/xml;charset=UTF-8
simpleClientSession: 123

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Header/>
   <soapenv:Body>
   <m0:placeOrder xmlns:m0="http://services.samples">
            <m0:order>
                <m0:price>172.23182849731984</m0:price>
                <m0:quantity>18398</m0:quantity>
                <m0:symbol>IBM</m0:symbol>
            </m0:order>
        </m0:placeOrder>
   </soapenv:Body>
</soapenv:Envelope>

Analyze the output

Out of the three instances of the Stock Quote service (Axis2 server), only one server acquires the sent request at a given time. When you send the requests, the WSO2 MI first receives the message and then routes it to the backend service (StockQuoteService). The following output will be printed on the Axis2 Server Console: 

Wed Aug 07 11:03:15 IST 2024 samples.services.SimpleStockQuoteService  :: Accepted order #1 for : 18398 stocks of IBM at $ 172.23182849731984
Wed Aug 07 11:03:17 IST 2024 samples.services.SimpleStockQuoteService  :: Accepted order #2 for : 18398 stocks of IBM at $ 172.23182849731984
Wed Aug 07 11:03:19 IST 2024 samples.services.SimpleStockQuoteService  :: Accepted order #3 for : 18398 stocks of IBM at $ 172.23182849731984

When inspecting the tcpmon, you will see that each listener has received a request (If you have only sent 3 requests, otherwise more than 1). This is because, when multiple requests are sent with the same session ID, they are distributed across the three endpoints in a round-robin manner.