streaming client support missing in websocket nodejs-ws-template.

[li-tianshu]

In order to leverage asyncapi for existing websocket services, the following supports are needed in nodejs-ws-template:

1. given a yaml specification, code generator needs to generate client that can connect to the websocket service and receive data in json format.
   For example, given the below websocket service URL (that streams some data to the client once connected):

        ws://admin:welcome@host1:port1/services/v2/stream1?begin=now

we can define a yaml API specification like below (note username password basic-auth and query parameter can be supported in different ways and this yaml is for demonstration only)

asyncapi: '2.2.0'
info:
  title: some data streaming API
  version: '1.0.0'
  description: |
    The demo API allows clients to subscribe to data
  license:
    name: Apache 2.0
    url: 'https://www.apache.org/licenses/LICENSE-2.0'
servers:
  myserver1:
    url: admin:Welcome_1@host1:port1
    protocol: ws

defaultContentType: application/json

channels:
  /services/v2/stream1:
    bindings:
      ws:
        bindingVersion: 0.1.0
        query:
          type: object
          description: query parameter like begin=now
          properties:
            begin:
              type: string
              default: now
              description: begin position to stream data
    subscribe:
      summary: data records
      operationId: onRecords
      message:
        name: records
        payload:
          type: object
          description: array of data records in json format

With this yaml definitioin for the websocket service, code generator should be able to generate client code in different languages such as node-js or python. Below is a sample node-js client code

const WebSocket = require('ws')

const serviceURL = 'ws://admin:welcome@host1:port1/services/v2/stream1?begin=now'

// generic data process with the websocket service
const processData = (wsClient) => {
	wsClient.on('message', function message(data) {
	    console.log('received some data:')
	    const records = eval(data.toString())
	    for (var i = 0; i < records.length; i++) {
		console.log(records[i]);
	    }
	});
	wsClient.on('error', (err) => {
	    console.log(err.toString());
        });
}
const init = async () =>{
    const wsClient = new WebSocket(serviceURL);
    // now streaming data
    processData(wsClient)
}

Here is an example client code in python in similar flow

#!/usr/bin/env python

import asyncio
import requests
import websockets
import json

async def processData():
        serviceURL = "ws://admin:welcome@host1:port1/services/v2/stream1?begin=now"
        async with websockets.connect(serviceURL) as websocket:
            print("start streaming data")
            while True:
                data = await websocket.recv()
                records = json.loads(data)
                for rec in records:
                    print("< {rec}")
asyncio.get_event_loop().run_until_complete(processData())

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[github-actions]

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[derberg]

closing as this is being implemented as new template -> https://github.com/tianshu-orcl/websocket-streaming-template