Startup and Shutdown¶
The ASGI lifespan specification includes the ability for awaiting
coroutines before the first byte is received and after the final byte
is sent, through the startup
and shutdown
lifespan events.
This is particularly useful for creating and destroying connection
pools. Quart supports this via the decorators
before_serving()
and
after_serving()
, which function like
before_first_request()
.
The decorated functions are all called within the app context,
allowing current_app
and g
to be used.
Warning
Use g
with caution, as it will reset after all the
before_serving
functions complete. It can still be used within
this context. If you want to create something used in routes, try
storing it on the app instead.
To use this functionality simply do the following:
@app.before_serving
async def create_db_pool():
app.db_pool = await ...
g.something = something
@app.before_serving
async def use_g():
g.something.do_something()
@app.route("/")
async def index():
app.db_pool.execute(...)
# g.something is not available here
@app.after_serving
async def create_db_pool():
await app.db_pool.close()
Testing¶
Quart’s default test client does not wait for the startup
and
shutdown
events. This must be manually added when testing a Quart
app using the before_serving
or after_serving
decorators. A
recommended pytest fixture is:
@pytest.fixture(name="app", scope="function")
async def _app():
app = create_app() # Initialize app
await app.startup()
yield app
await app.shutdown()
The app fixture can then be used as normal.
@pytest.mark.asyncio
async def test_index(app):
test_client = app.test_client()
await test_client.get("/")
...