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Publishing HTTP Requests, Receiving Responses, and Processing Them

Purpose:

This application demonstrates how to configure WSO2 Integrator: SI Tooling to send sweet production events via HTTP transport in JSON default format, Receive response from the http server and process the response using siddhi.

Prerequisites:

  • Save this sample. If there is no syntax error, the following message is shown on the console:
    • Siddhi App HttpRequestResponseSample successfully deployed.

Executing the Sample:

  1. Start the Siddhi application by clicking on 'Run'.
  2. If the Siddhi application starts successfully, the following messages are shown on the console:
  3. HttpRequestResponseSample.siddhi - Started Successfully!
  4. 'Http' sink at 'LowProductionAlertStream' stream successfully connected to 'localhost:8080/abc'.

Testing the Sample:

  1. Open a terminal and navigate to {WSO2SIHome}/samples/sample-clients/http-server and run "ant" command without any arguments.

  2. Send events using one or more of the following methods.

    • Send events with http server through the event simulator:

      1. Open the event simulator by clicking on the second icon or pressing Ctrl+Shift+I.
      2. In the Single Simulation tab of the panel, specifiy the values as follows:
        • Siddhi App Name : HttpRequestResponseSample
        • Stream Name : SweetProductionStream
      3. In the name and amount fields, enter 'toffees' and '75.6' respectively and then click Send to send the event.
      4. Send more events as desired.

    • Send events to the HTTP endpoint defined by 'publish.url' in the Sink configuration using the curl command:

      1. Open a new terminal and issue the following command:
        • curl -X POST -d '{"streamName": "SweetProductionStream", "siddhiAppName": "HttpRequestResponseSample","data": ['toffees', 75.6]}' http://localhost:9390/simulation/single -H 'content-type: text/plain'
      2. If there is no error, the following messages are shown on the terminal:
        • {"status":"OK","message":"Single Event simulation started successfully"}

    • Publish events with Postman:

      1. Install the 'Postman' application from Chrome web store.
      2. Launch the application.
      3. Make a 'Post' request to the 'http://localhost:9390/simulation/single' endpoint. Set the Content-Type to 'text/plain' and set the request body in text as follows:
      4. Click 'send'. If there is no error, the following messages are shown on the console:
        • "status": "OK",
        • "message": "Single Event simulation started successfully"
    • When publishing the events, http-request sink will send the request to the http server and the server will echo the received request as the response with a 200 http status code. Then,
    • That successful response will be received by the defined http-response source which has the relevant http status code.
    • Received response will be converted to a siddhi event using using json default mapping and pushed to the ResponseStream.

Viewing the Results:

The received responses will be logged in the terminal/editor console as following.

  • INFO {io.siddhi.core.stream.output.sink.LogSink} - RequestResponse : responseStream : Event{timestamp=1555358941592, data=[toffees, 75.6], isExpired=false}

Notes:

If the message "LowProductionAlertStream' stream could not connect to 'localhost:8080", it could be due to port 8080 defined in the Siddhi application is already being used by a different program. To resolve this issue, do the following: 1. Stop this Siddhi application (Click 'Run' on menu bar -> 'Stop'). 2. Change the port from 8080 to an unused port in this Siddhi application's source configuration and in the http-server file. 3. Start the application and check whether the expected output appears on the console.

@App:name("HttpRequestResponseSample")
@App:description("Publish http requests, receive their responses and process them")


define stream SweetProductionStream (name string, amount double);

@sink(type='http-request', sink.id='production-request', publisher.url='http://localhost:8080/abc',
@map(type='json'))
define stream LowProductionAlertStream (name string, amount double);

@sink(type='log')
@source(type='http-response' , sink.id='production-request', http.status.code='200',
@map(type='json'))
define stream ResponseStream(name string, amount double);

@info(name='query1')
from SweetProductionStream
select *
insert into LowProductionAlertStream;