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Deploy to Fly
================
This guide describes how to deploy a websockets server to Fly_.
.. _Fly: https://fly.io/
.. admonition:: The free tier of Fly is sufficient for trying this guide.
:class: tip
The `free tier`__ include up to three small VMs. This guide uses only one.
__ https://fly.io/docs/about/pricing/
We're going to deploy a very simple app. The process would be identical for a
more realistic app.
Create application
------------------
Here's the implementation of the app, an echo server. Save it in a file called
``app.py``:
.. literalinclude:: ../../example/deployment/fly/app.py
:language: python
This app implements typical requirements for running on a Platform as a Service:
* it provides a health check at ``/healthz``;
* it closes connections and exits cleanly when it receives a ``SIGTERM`` signal.
Create a ``requirements.txt`` file containing this line to declare a dependency
on websockets:
.. literalinclude:: ../../example/deployment/fly/requirements.txt
:language: text
The app is ready. Let's deploy it!
Deploy application
------------------
Follow the instructions__ to install the Fly CLI, if you haven't done that yet.
__ https://fly.io/docs/hands-on/install-flyctl/
Sign up or log in to Fly.
Launch the app — you'll have to pick a different name because I'm already using
``websockets-echo``:
.. code-block:: console
$ fly launch
Creating app in ...
Scanning source code
Detected a Python app
Using the following build configuration:
Builder: paketobuildpacks/builder:base
? App Name (leave blank to use an auto-generated name): websockets-echo
? Select organization: ...
? Select region: ...
Created app websockets-echo in organization ...
Wrote config file fly.toml
? Would you like to set up a Postgresql database now? No
We have generated a simple Procfile for you. Modify it to fit your needs and run "fly deploy" to deploy your application.
.. admonition:: This will build the image with a generic buildpack.
:class: tip
Fly can `build images`__ with a Dockerfile or a buildpack. Here, ``fly
launch`` configures a generic Paketo buildpack.
If you'd rather package the app with a Dockerfile, check out the guide to
:ref:`containerize an application <containerize-application>`.
__ https://fly.io/docs/reference/builders/
Replace the auto-generated ``fly.toml`` with:
.. literalinclude:: ../../example/deployment/fly/fly.toml
:language: toml
This configuration:
* listens on port 443, terminates TLS, and forwards to the app on port 8080;
* declares a health check at ``/healthz``;
* requests a ``SIGTERM`` for terminating the app.
Replace the auto-generated ``Procfile`` with:
.. literalinclude:: ../../example/deployment/fly/Procfile
:language: text
This tells Fly how to run the app.
Now you can deploy it:
.. code-block:: console
$ fly deploy
... lots of output...
==> Monitoring deployment
1 desired, 1 placed, 1 healthy, 0 unhealthy [health checks: 1 total, 1 passing]
--> v0 deployed successfully
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:
.. code-block:: console
$ python -m venv websockets-client
$ . websockets-client/bin/activate
$ pip install websockets
Connect the interactive client — you must replace ``websockets-echo`` with the
name of your Fly app in this command:
.. code-block:: console
$ python -m websockets wss://websockets-echo.fly.dev/
Connected to wss://websockets-echo.fly.dev/.
>
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:
.. code-block:: console
> Hello!
< Hello!
Connection closed: 1000 (OK).
You can also confirm that your application shuts down gracefully.
Connect an interactive client again — remember to replace ``websockets-echo``
with your app:
.. code-block:: console
$ python -m websockets wss://websockets-echo.fly.dev/
Connected to wss://websockets-echo.fly.dev/.
>
In another shell, restart the app — again, replace ``websockets-echo`` with your
app:
.. code-block:: console
$ fly restart websockets-echo
websockets-echo is being restarted
Go back to the first shell. The connection is closed with code 1001 (going
away).
.. code-block:: console
$ python -m websockets wss://websockets-echo.fly.dev/
Connected to wss://websockets-echo.fly.dev/.
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).
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