There are situations where you may not want to run the HTTP server in a
full blown WSGI-over-Tornado container - unit/integration tests and
embedded single-core devices are among those cases.
In those scenarios, we should allow the user to be able to run the
backend using the built-in Werkzeug server provided by Flask.
This reverts commit 71401a4936.
Temporarily reverted this commit because the `reuse_address` on the
application's `listen` method has only been implemented in Tornado 6.2 -
and Debian stable still shipts Tornado 6.1.
The WSGI container is a good option to wrap a multi-modal webapp
(Flask + websocket routes), but it's constrained to a single-process
approach and queued/pre-buffered requests. That makes performance poor
when handling requests that may take a few seconds to complete.
Defined a `platypush.backend.http.ws` package with all the routes, a
base `WSRoute` class that all the websocket routes can extend, and a
logic in the HTTP backend to automatically scan the package to register
exposed websocket routes.
It was just too painful to find a combination of versions of gunicorn,
gevent, eventlet, pyuwsgi etc. that could work on all of my systems.
On the other hand, Tornado works out of the box with no headaches.
Also in this commit:
- Updated a bunch of outdated/required integration dependencies.
- Black'd and LINTed a couple of old plugins.
The eventlet API has way too many dependency issues with gunicorn.
Still TODO: Fix or at least mitigate the WSGI workers timeout issue when
they handle websocket connections.
The websocket service is no longer provided by a different service,
controlled by a different thread running on another port.
Instead, it's now exposed directly over Flask routes, using
WSGI+eventlet+simple_websocket.
Also, the SSL context options have been removed from `backend.http`, for
sake of simplicity. If you want to enable SSL, you can serve Platypush
through a reverse proxy like nginx.
Added `waitress` dependency. For performance and security reasons, it's
better to always run the Flask application inside of a uWSGI server.
`waitress` also makes things easier by avoiding to ask the user to
manually provide the external executable arguments, as it was the case
with `uwsgi` and `gunicorn`.
- Better synchronization logic on stop for `AsyncRunnablePlugin`.
- Fixed several thread names by dropping `prctl.set_name` in favour of
specifying the name directly on thread creation.
- Several LINT fixes.
The Zeroconf registration part may randomly get stuck, resulting in the
web server not being properly started.
It's therefore better to run the Zeroconf registration process
asynchronously, for it's not strictly required for the web server to
execute.
If Platypush is supposed to work also without a manually created
`config.yaml`, and the HTTP backend is enabled by default in that
configuration, then Flask and companions should be among the required
dependencies.
gunicorn makes it easier to set up a uWSGI wrapper
around the web application, and it's easier to
install and document than handling uwsgi as an
external system dependency.
If multiple threads process events and notify the websocket
clients at the same time then we may end up with inconsistent
messages delivered on the websocket (and websockets is not
designed to handle such cases). Protecting the send call with
a per-socket lock makes sure that we only write one message
at the time for a certain client.
Fabio Manganiello
Fabio Manganiello