How to communicate my Rest Api Server with my Web Socket server

Question

Here is my problem that is partially resolved but not in the best way I think. I have a REST API Server that has a method POST that only executes a batch process. The method immediately returns 200 (without any body) and the batch process continues its task in the server. This batch process has a logging file, that I usually see online with tail -f mylogfile.log. What I want now is to use a websocket server to send the output of the tail process to webpage. The code of the websocket server look like this:

import os
import asyncio
import websockets
import subprocess

from frontserv.start_server import WEBSOCKET_INTERCHANGE_FILE


async def main(websocket, path):
    print("-> STARTING")
    exists = os.path.isfile(WEBSOCKET_INTERCHANGE_FILE)
    if not exists:
        f = open(WEBSOCKET_INTERCHANGE_FILE, "w+")
        f.close()

    exe = ["tail", "-f", WEBSOCKET_INTERCHANGE_FILE]
    message = ""
    p = subprocess.Popen(exe, stdout=subprocess.PIPE, stderr=None)
    while True:
        retcode = p.poll()
        print(message)
        message = message + p.stdout.readline().decode("utf-8") + "<br>"
        await websocket.send(message)
        await asyncio.sleep(0.1)


start_server = websockets.serve(main, '127.0.0.1', 5678)
asyncio.get_event_loop().run_until_complete(start_server)
asyncio.get_event_loop().run_forever()

I have access to the batch process code, and I think there is a better way to resolve this. If instead of logging to a file I could send a message to the websocket server to dispatch a message to the browser, I think it would be a better implementation.

Best regards!

Answer 1

If you just want to send the output of a process to a client via websockets, I would suggest you look at websocketd

You just tell it a port to listen on, and a command to run

$ websocketd --port=8080 my-program

And it will run the command when a client connects and serve them the output.