Implement web.run_app utility function

aiohttp/web.py

@@ -287,3 +287,37 @@ def __call__(self):
 
     def __repr__(self):
         return "<Application>"
+
+
+def run_app(app, *, host='0.0.0.0', port=None,
+            shutdown_timeout=60.0, ssl_context=None):
+    """Run an app locally"""
+    if port is None:
+        if not ssl_context:
+            port = 8080
+        else:
+            port = 8443
+
+    loop = app.loop
+
+    handler = app.make_handler()
+    srv = loop.run_until_complete(loop.create_server(handler, host, port,
+                                                     ssl=ssl_context))
+
+    scheme = 'https' if ssl_context else 'http'
+    prompt = '127.0.0.1' if host == '0.0.0.0' else host
+    print("======== Running on {scheme}://{prompt}:{port}/ ========\n"
+          "(Press CTRL+C to quit)".format(
+              scheme=scheme, prompt=prompt, port=port))
+
+    try:
+        loop.run_forever()
+    except KeyboardInterrupt:  # pragma: no branch
+        pass
+    finally:
+        srv.close()
+        loop.run_until_complete(srv.wait_closed())
+        loop.run_until_complete(app.shutdown())
+        loop.run_until_complete(handler.finish_connections(shutdown_timeout))
+        loop.run_until_complete(app.finish())
+    loop.close()

docs/web.rst

@@ -32,27 +32,16 @@ particular *HTTP method* and *path*::
    app = web.Application()
    app.router.add_route('GET', '/', hello)
 
-After that, create a server and run the *asyncio loop* as usual::
+After that, run the application by :func:`run_app` call::
 
-   loop = asyncio.get_event_loop()
-   handler = app.make_handler()
-   f = loop.create_server(handler, '0.0.0.0', 8080)
-   srv = loop.run_until_complete(f)
-   print('serving on', srv.sockets[0].getsockname())
-   try:
-       loop.run_forever()
-   except KeyboardInterrupt:
-       pass
-   finally:
-       srv.close()
-       loop.run_until_complete(srv.wait_closed())
-       loop.run_until_complete(app.on_shutdown.send())
-       loop.run_until_complete(handler.finish_connections(1.0))
-       loop.run_until_complete(app.finish())
-   loop.close()
+   run_app(app)
 
 That's it. Now, head over to ``http://localhost:8080/`` to see the results.
 
+.. seealso:: :ref:`aiohttp-web-graceful-shutdown` section
+             explains what :func:`run_app` does and how implement
+             complex server initialization/finalization from scratch.
+
 
 .. _aiohttp-web-handler:
 
@@ -834,9 +823,22 @@ Signal handler may looks like:
 
     app.on_shutdown.append(on_shutdown)
 
+Proper finalization procedure has three steps:
 
-Server finalizer should raise shutdown signal by
-:meth:`Application.shutdown` call::
+  1. Stop accepting new client connections by
+     :meth:`asyncio.Server.close` and
+     :meth:`asyncio.Server.wait_closed` calls.
+
+  2. Fire :meth:`Application.shutdown` event.
+
+  3. Close accepted connections from clients by
+     :meth:`RequestHandlerFactory.finish_connections` call with
+     reasonable small delay.
+
+  4. Call registered application finalizers by :meth:`Application.finish`.
+
+The following code snippet performs proper application start, run and
+finalizing.  It's pretty close to :func:`run_app` utility function::
 
    loop = asyncio.get_event_loop()
    handler = app.make_handler()
@@ -857,6 +859,7 @@ Server finalizer should raise shutdown signal by
 
 
 
+
 CORS support
 ------------
 

docs/web_reference.rst

@@ -1511,6 +1511,41 @@ Utilities
    .. seealso:: :ref:`aiohttp-web-file-upload`
 
 
+.. function:: run_app(app, *, host='0.0.0.0', port=None, loop=None, \
+                      shutdown_timeout=60.0, ssl_context=None)
+
+   An utility function for running an application, serving it until
+   keyboard interrupt and performing a
+   :ref:`aiohttp-web-graceful-shutdown`.
+
+   Suitable as handy tool for scaffolding aiohttp based projects.
+   Perhaps production config will use more sophisticated runner but it
+   good enough at least at very beginning stage.
+
+   The function uses *app.loop* as event loop to run.
+
+   :param app: :class:`Application` instance to run
+
+   :param str host: host for HTTP server, ``'0.0.0.0'`` by default
+
+   :param int port: port for HTTP server. By default is ``8080`` for
+                    plain text HTTP and ``8443`` for HTTP via SSL
+                    (when *ssl_context* parameter is specified).
+
+   :param int shutdown_timeout: a delay to wait for graceful server
+                                shutdown before disconnecting all
+                                open client sockets hard way.
+
+                                A system with properly
+                                :ref:`aiohttp-web-graceful-shutdown`
+                                implemented never waits for this
+                                timeout but closes a server in a few
+                                milliseconds.
+
+   :param ssl_context: :class:`ssl.SSLContext` for HTTPS server,
+                       ``None`` for HTTP connection.
+
+
 Constants
 ---------
 

tests/conftest.py

@@ -164,7 +164,7 @@ def loop(request):
     yield loop
 
     if not loop._closed:
-        loop.stop()
+        loop.call_soon(loop.stop)
         loop.run_forever()
         loop.close()
     gc.collect()

tests/test_run_app.py

@@ -0,0 +1,46 @@
+import asyncio
+import ssl
+
+from unittest import mock
+from aiohttp import web
+
+
+def test_run_app_http(loop):
+    loop = mock.Mock(spec=asyncio.AbstractEventLoop, wrap=loop)
+    loop.call_later(0.01, loop.stop)
+
+    app = web.Application(loop=loop)
+
+    web.run_app(app)
+
+    loop.close.assert_called_with()
+    loop.create_server.assert_called_with(mock.ANY, '0.0.0.0', 8080, ssl=None)
+
+
+def test_run_app_https(loop):
+    loop = mock.Mock(spec=asyncio.AbstractEventLoop, wrap=loop)
+    loop.call_later(0.01, loop.stop)
+
+    app = web.Application(loop=loop)
+
+    ssl_context = ssl.create_default_context()
+
+    web.run_app(app, ssl_context=ssl_context)
+
+    loop.close.assert_called_with()
+    loop.create_server.assert_called_with(mock.ANY, '0.0.0.0', 8443,
+                                          ssl=ssl_context)
+
+
+def test_run_app_nondefault_host_port(loop, unused_port):
+    port = unused_port()
+    host = 'localhost'
+
+    loop = mock.Mock(spec=asyncio.AbstractEventLoop, wrap=loop)
+    loop.call_later(0.01, loop.stop)
+
+    app = web.Application(loop=loop)
+
+    web.run_app(app, host=host, port=port)
+
+    loop.create_server.assert_called_with(mock.ANY, host, port, ssl=None)