TIL: Autoloading on Filechange using Watchdog

Using Watchdog to monitor changes to a directory so we can alter what we serve out as HTTP. Each segment is the evolution towards getting it to work.

Serving HTTP from a directory

I've done this for ages:

python -m http.server 8000 -d /path/to/files

Using http.server in a function

The Python docs aren't very clear on this, and rather than think hard about it I did this fun hack:

# cli.py
from pathlib import Path
from subprocess import check_call

def server(site: Path) -> None:
    check_call(['python', '-m', 'http.server', '8000', '-d', site])

Autoreloading on filechanges

A bit more involved, and can certainly be improved. Here goes:

# server.py
import functools
import http.server
import os
import socketserver
from pathlib import Path

from watchdog.events import FileSystemEventHandler
from watchdog.observers import Observer


def build_handler(directory: Path):
    """Specify the directory of SimpleHTTPRequestHandler"""
    return functools.partial(http.server.SimpleHTTPRequestHandler, directory=directory)


class EventHandler(FileSystemEventHandler):
    def on_any_event(self, event):
        if event.is_directory:
            return
        elif event.event_type in ["created", "modified"]:
            print(f"Reloading server due to file change: {event.src_path}")
            os._exit(0)


def run_server(directory: Path, port: int = 8000):
    with socketserver.TCPServer(("", port), build_handler(directory)) as httpd:
        print(f"Serving on port {port}")
        httpd.serve_forever()


def server(directory: Path, port: int = 8000):
    """Serve files in the watched directory"""
    # Watch the directory
    event_handler = EventHandler()
    observer = Observer()
    observer.schedule(event_handler, site, recursive=True)
    observer.start()

    try:
        # Run the HTTP server
        run_server(directory=directory, port=port)
    except KeyboardInterrupt:
        observer.stop()

    observer.join()

Usage:

# cli.py
from .server import server

def serve(site: Path, port: int = 8000):
    server(site="/path/to/directory/of/html", port=7500)