Notify python orion/quantumleap subscription changes

Question

Is there any way to get notified in python when a Quantumleap o Orion subscription fires for a changed value?

Answer 1

I've dockerized the nickjj web server, switched the bind_host to 0.0.0.0 as specified in the documentation, and exposed the port 8008:8008 in docker-compose.

nickjj Python web server:

from http.server import HTTPServer, BaseHTTPRequestHandler
from sys import argv

BIND_HOST = '0.0.0.0'
PORT = 8008

class SimpleHTTPRequestHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.write_response(b'')

    def do_POST(self):
        content_length = int(self.headers.get('content-length', 0))
        body = self.rfile.read(content_length)

        self.write_response(body)

    def write_response(self, content):
        self.send_response(200)
        self.end_headers()
        self.wfile.write(content)

        print(self.headers)
        print(content.decode('utf-8'))


if len(argv) > 1:
    arg = argv[1].split(':')
    BIND_HOST = arg[0]
    PORT = int(arg[1])

print(f'Listening on http://{BIND_HOST}:{PORT}\n')

httpd = HTTPServer((BIND_HOST, PORT), SimpleHTTPRequestHandler)
httpd.serve_forever()

Dockerfile to build the web server service:

# Build the service from the base image
FROM python:3.9.16-alpine3.17

# During building, run the following commands to install dependecies
RUN apk add --no-cache openssl-dev curl-dev
RUN pip install --upgrade pip
# RUN pip install pycurl crate requests

# Set the work directory
WORKDIR /webserver

# Copy in the continer the following files
COPY ./webserver ./webserver

# Run this command at startup
CMD ["python","-u","webserver", "webserver:8008"]

docker-compose configuration for the web server, with curl for debug:

webserver:
  image: webserver
  stdin_open: true # docker run -i
  tty: true        # docker run -t
  container_name: 'webserver'
  ports:
    - "8008:8008"
  networks:
    - default

I've provisioned the relative subscription in Orion:

curl -iX POST \
    'http://localhost:1026/v2/subscriptions/' \
    -H 'Content-Type: application/json' \
    -H 'fiware-service: opcua_car' \
    -H 'fiware-servicepath: /demo' \
    -d '{
  "description": "Subscriptions for Python webserver",
  "subject": {
    "entities": [
      {
        "idPattern": ".*",
        "type": "PLC"
      }
    ],
    "condition": {
      "attrs": [
        "processStatus"
      ]
    }
  },
  "notification": {
    "http": {
      "url": "http://webserver:8008/"
    },
    "attrs": [
      "processStatus"
    ],
    "metadata": [
      "dateCreated",
      "dateModified"
    ]
  },
  "throttling": 1
}'

And I finally get my subscription notifications in Python.