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Integrating Micro Integrator with WSO2 Streaming Integrator

You can publish events from the integration flow to WSO2 Streaming Integrator using an http or http-service source configured in a Siddhi application deployed in Streaming Integrator server. The http or http-service source receive POST requests via HTTP and HTTPS protocols in a format such as text, XML, or JSON. In the case of http-service source, it will send responses via its corresponding http-service-response sink correlated through a unique source.id.

In this example, we are using a simple rest API to publish events to the Streaming Integrator, which is configured to receive POST requests via HTTP protocol in JSON format and send responses accordingly.

Set up the Siddhi Application

Follow the instructions below to set up and configure.

1. Download and install the Streaming Integrator.

2. Start and create the following Siddhi application.

   Note

   This “ShoppingCart” siddhi app demonstrates a simple scenario where you can add an item to a shopping cart and see the total cost. The siddhi app will receive events via HTTP protocol in JSON format with a custom mapping.

   @App:name("ShoppingCart")
   
   @App:description('Receive events via HTTP transport in JSON format with custom mapping and view the output on the console')
   
   @source(type='http-service', receiver.url='http://localhost:5005/addToCart',
         source.id='adder', basic.auth.enabled='false', @map(type='json', 
         @attributes(messageId='trp:messageId', name='$.event.name', price='$.event.price')))
   define stream AddStream (messageId string, name String, price double);
   
   @sink(type='http-service-response', source.id='adder', message.id='', @map(type = 'json'))
   define stream ResultStream (messageId string, message string, numOfItems long, totalCost double);
   
   @info(name = 'query1')
   from AddStream 
   select  messageId, str:concat('Successfully added ', name, ' to the cart') as message, count() as numOfItems, sum(price) as totalCost
   insert into ResultStream;

   The http-service source on stream AddStream listens on url http://localhost:5005/addToCart for JSON messages with format:

   {
     "event": {
       "name": "Cheese",
       "Price": 390
     }
   }

   and when events arrive, it maps to AddStream events and passes them to query named query1 for processing. The query results produced on ResultStream are sent as a response via http-service-response sink with format:

   {
     "event": {
       "messageId":"741f30af-89c8-44ce-abbc-8ded26a4c4b7",
       "message":"Successfully added Cheese to the cart",
       "numOfItems":1,
       "totalCost":390.0
     }
   }

3. Deploy the application in the Streaming Integrator.

Synapse configuration

Following is the sample rest API configuration that we can use to implement this scenario. See the instructions on how to build and run run this example.

<api xmlns="http://ws.apache.org/ns/synapse" name="OrderAPI" context="/addToCart"> 
   <resource methods="POST" url-mapping="/"> 
      <inSequence> 
         <send> 
            <endpoint>
               <address uri="http://localhost:5005/addToCart"/>
         </endpoint>
         </send> 
      </inSequence> 
   </resource> 
</api>

Build and run

Create the artifacts:

1. Set up WSO2 Integration Studio.
2. Create an ESB Solution project.
3. Create the rest API with the configurations given above.
4. Deploy the artifacts in your Micro Integrator.

Invoke the sample API:

• Open a terminal and execute the following CURL command. This sends a simple POST request to the Micro Integrator.

  curl -X POST -d "{\"event\":{\"name\":\"snacks\",\"price\":10.0}}" http://localhost:8290/addToCart --header "Content-Type:application/json"

• You will receive the following response in the console in which you are running the MI server:

  {"event":{"messageId":"7b0da3c2-ddae-4627-8c43-fa09faa1abb7","message":"Successfully added snacks to the cart","numOfItems":1,"totalCost":10.0}}

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