Added `use_werkzeug_server` option to `backend.http`.

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.

platypush/backend/http/__init__.py

@@ -199,6 +199,7 @@ class HttpBackend(Backend):
         resource_dirs: Optional[Mapping[str, str]] = None,
         secret_key_file: Optional[str] = None,
         num_workers: Optional[int] = None,
+        use_werkzeug_server: bool = False,
         **kwargs,
     ):
         """
@@ -211,6 +212,16 @@ class HttpBackend(Backend):
         :param secret_key_file: Path to the file containing the secret key that will be used by Flask
             (default: ``~/.local/share/platypush/flask.secret.key``).
         :param num_workers: Number of worker processes to use (default: ``(cpu_count * 2) + 1``).
+        :param use_werkzeug_server: Whether the backend should be served by a
+            Werkzeug server (default: ``False``). Note that using the built-in
+            Werkzeug server instead of Tornado is very inefficient, and it
+            doesn't support websocket-based features either so the UI will
+            probably be severely limited. You should only use this option if:
+
+                - You are running tests.
+                - You have issues with running a full Tornado server - for
+                  example, you are running the application on a small embedded
+                  device that doesn't support Tornado.
         """
 
         super().__init__(**kwargs)
@@ -235,6 +246,7 @@ class HttpBackend(Backend):
         )
         self.local_base_url = f'http://localhost:{self.port}'
         self.num_workers = num_workers or (cpu_count() * 2) + 1
+        self.use_werkzeug_server = use_werkzeug_server
 
     def send_message(self, *_, **__):
         self.logger.warning('Use cURL or any HTTP client to query the HTTP backend')
@@ -339,14 +351,25 @@ class HttpBackend(Backend):
             self.num_workers,
         )
 
-        sockets = bind_sockets(self.port, address=self.bind_address, reuse_port=True)
+        if self.use_werkzeug_server:
+            application.config['redis_queue'] = self.bus.redis_queue
+            application.run(
+                host=self.bind_address,
+                port=self.port,
+                use_reloader=False,
+                debug=True,
+            )
+        else:
+            sockets = bind_sockets(
+                self.port, address=self.bind_address, reuse_port=True
+            )
 
-        try:
-            fork_processes(self.num_workers)
-            future = self._post_fork_main(sockets)
-            asyncio.run(future)
-        except (asyncio.CancelledError, KeyboardInterrupt):
-            return
+            try:
+                fork_processes(self.num_workers)
+                future = self._post_fork_main(sockets)
+                asyncio.run(future)
+            except (asyncio.CancelledError, KeyboardInterrupt):
+                return
 
     def _start_web_server(self):
         self._server_proc = Process(target=self._web_server_proc)

tests/conftest.py

@@ -1,9 +1,10 @@
 import logging
 import os
-import pytest
 import time
 from threading import Thread
 
+import pytest
+
 from platypush import Daemon, Config
 
 from .utils import config_file, set_base_url
@@ -17,8 +18,6 @@ def clear_loggers():
     This is to prevent pytest spitting out logging errors on teardown if the logging objects have been deinitialized
     (see https://github.com/pytest-dev/pytest/issues/5502#issuecomment-647157873).
     """
-    import logging
-    # noinspection PyUnresolvedReferences
     loggers = [logging.getLogger()] + list(logging.Logger.manager.loggerDict.values())
     for logger in loggers:
         handlers = getattr(logger, 'handlers', [])
@@ -31,31 +30,34 @@ def app():
     logging.info('Starting Platypush test service')
 
     Config.init(config_file)
-    app = Daemon(config_file=config_file, redis_queue='platypush-tests/bus')
-    Thread(target=lambda: app.run()).start()
-    logging.info('Sleeping {} seconds while waiting for the daemon to start up'.format(app_start_timeout))
+    _app = Daemon(config_file=config_file, redis_queue='platypush-tests/bus')
+    Thread(target=_app.run).start()
+    logging.info(
+        'Sleeping %d seconds while waiting for the daemon to start up',
+        app_start_timeout,
+    )
     time.sleep(app_start_timeout)
-    yield app
+    yield _app
 
     logging.info('Stopping Platypush test service')
-    app.stop_app()
+    _app.stop_app()
     clear_loggers()
-    db_file = (Config.get('main.db') or {}).get('engine', '')[len('sqlite:///'):]
+    db = (Config.get('main.db') or {}).get('engine', '')[len('sqlite:///') :]
 
-    if db_file and os.path.isfile(db_file):
-        logging.info('Removing temporary db file {}'.format(db_file))
-        os.unlink(db_file)
+    if db and os.path.isfile(db):
+        logging.info('Removing temporary db file %s', db)
+        os.unlink(db)
 
 
 @pytest.fixture(scope='session')
 def db_file():
-    yield Config.get('main.db')['engine'][len('sqlite:///'):]
+    yield Config.get('main.db')['engine'][len('sqlite:///') :]
 
 
 @pytest.fixture(scope='session')
 def base_url():
     backends = Config.get_backends()
     assert 'http' in backends, 'Missing HTTP server configuration'
-    url = 'http://localhost:{port}'.format(port=backends['http']['port'])
+    url = f'http://localhost:{backends["http"]["port"]}'
     set_base_url(url)
     yield url

tests/etc/config_test.yaml

@@ -6,7 +6,8 @@ main.db:
 
 backend.http:
     port: 8123
-    disable_websocket: True
+    num_workers: 1
+    use_werkzeug_server: True
 
 backend.redis:
     disabled: False