generate and stream output of a command over HTTP on demand

Question

I'm doing a little Swiss Army Linuxing right now. I've run into a situation where I want to run a command, then pipe it into an HTTP server, which serves just that stream. Here's the whole scenario:

1. Start the server with a line like

    $ httpondemand parecord 

   Server does not start parecord right away.

2. HTTP client connects.

    $ wget -O - http://server/ | mpv - 

   I CAN HAZ "/" ?

3. Server: Start parecord, get some output, reply "200 sigh , faaain,", send output.

I am about to write the tool myself, but I thought I'd ask if there were anything already capable of this.

Answer 1

I couldn't find a tool that could do this, so I did end up writing one, which for reasons beyond the scope of this document, was named todd . I'd still rather use something that already exists, so this is not my ideal solution.

#!/usr/bin/env python

from socketserver import TCPServer
from http.server import BaseHTTPRequestHandler
import subprocess as sp
from sys import *

class ToddHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.end_headers()

        # Do not start the command until after a connection has been made.
        p = sp.Popen(argv[1:], stdout=sp.PIPE)
        while True:
            data = p.stdout.read(1024)
            if len(data) == 0:
                break

            try:
                self.wfile.write(data)
            except BrokenPipeError:
                break
            except ConnectionResetError:
                break
        p.stdout.close()
        p.wait()  # Kill the zombie.

if len(argv) == 1:
    stderr.write('usage: todd command [arg1 arg2 ...]\n')

# Create the server.
server = TCPServer(('', 10000), ToddHandler)

# Activate the server; this will keep running until you
# interrupt the program with Ctrl-C
server.serve_forever()