Deploy to Koyeb

This guide describes how to deploy a websockets server to Koyeb.

The free tier of Koyeb is sufficient for trying this guide.

The free tier include one web service, which this guide uses.

We’re going to deploy a very simple app. The process would be identical to a more realistic app.

Create repository

Koyeb supports multiple deployment methods. Its quick start guides recommend git-driven deployment as the first option. Let’s initialize a git repository:

$ mkdir websockets-echo
$ cd websockets-echo
$ git init -b main
Initialized empty Git repository in websockets-echo/.git/
$ git commit --allow-empty -m "Initial commit."
[main (root-commit) 740f699] Initial commit.

Render requires the git repository to be hosted at GitHub.

Sign up or log in to GitHub. Create a new repository named websockets-echo. Don’t enable any of the initialization options offered by GitHub. Then, follow instructions for pushing an existing repository from the command line.

After pushing, refresh your repository’s homepage on GitHub. You should see an empty repository with an empty initial commit.

Create application

Here’s the implementation of the app, an echo server. Save it in a file called app.py:

#!/usr/bin/env python

import asyncio
import http
import os
import signal

from websockets.asyncio.server import serve


async def echo(websocket):
    async for message in websocket:
        await websocket.send(message)


def health_check(connection, request):
    if request.path == "/healthz":
        return connection.respond(http.HTTPStatus.OK, "OK\n")


async def main():
    port = int(os.environ["PORT"])
    async with serve(echo, "", port, process_request=health_check) as server:
        loop = asyncio.get_running_loop()
        loop.add_signal_handler(signal.SIGTERM, server.close)
        await server.wait_closed()


if __name__ == "__main__":
    asyncio.run(main())

This app implements typical requirements for running on a Platform as a Service:

  • it listens on the port provided in the $PORT environment variable;

  • it provides a health check at /healthz;

  • it closes connections and exits cleanly when it receives a SIGTERM signal; while not documented, this is how Koyeb terminates apps.

Create a requirements.txt file containing this line to declare a dependency on websockets:

websockets

Create a Procfile to tell Koyeb how to run the app.

web: python app.py

Confirm that you created the correct files and commit them to git:

$ ls
Procfile         app.py           requirements.txt
$ git add .
$ git commit -m "Initial implementation."
[main f634b8b] Initial implementation.
 3 files changed, 39 insertions(+)
 create mode 100644 Procfile
 create mode 100644 app.py
 create mode 100644 requirements.txt

The app is ready. Let’s deploy it!

Deploy application

Sign up or log in to Koyeb.

In the Koyeb control panel, create a web service with GitHub as the deployment method. Install and authorize Koyeb’s GitHub app if you haven’t done that yet.

Follow the steps to create a new service:

  1. Select the websockets-echo repository in the list of your repositories.

  2. Confirm that the Free instance type is selected. Click Next.

  3. Configure health checks: change the protocol from TCP to HTTP and set the path to /healthz. Review other settings; defaults should be correct. Click Deploy.

Koyeb builds the app, deploys it, verifies that the health checks passes, and makes the deployment active.

Validate deployment

Let’s confirm that your application is running as expected.

Since it’s a WebSocket server, you need a WebSocket client, such as the interactive client that comes with websockets.

If you’re currently building a websockets server, perhaps you’re already in a virtualenv where websockets is installed. If not, you can install it in a new virtualenv as follows:

$ python -m venv websockets-client
$ . websockets-client/bin/activate
$ pip install websockets

Look for the URL of your app in the Koyeb control panel. It looks like https://<app>-<user>-<id>.koyeb.app/. Connect the interactive client — you must replace https with wss in the URL:

$ websockets wss://<app>-<user>-<id>.koyeb.app/
Connected to wss://<app>-<user>-<id>.koyeb.app/.
>

Great! Your app is running!

Once you’re connected, you can send any message and the server will echo it, or press Ctrl-D to terminate the connection:

> Hello!
< Hello!
Connection closed: 1000 (OK).

You can also confirm that your application shuts down gracefully.

Connect an interactive client again:

$ websockets wss://<app>-<user>-<id>.koyeb.app/
Connected to wss://<app>-<user>-<id>.koyeb.app/.
>

In the Koyeb control panel, go to the Settings tab, click Pause, and confirm.

Eventually, the connection gets closed with code 1001 (going away).

$ websockets wss://<app>-<user>-<id>.koyeb.app/
Connected to wss://<app>-<user>-<id>.koyeb.app/.
Connection closed: 1001 (going away).

If graceful shutdown wasn’t working, the server wouldn’t perform a closing handshake and the connection would be closed with code 1006 (abnormal closure).