timing-asgi

This is a timing middleware for ASGI, useful for automatic instrumentation of ASGI endpoints.

This was developed at GRID for use with our backend services which are built using python and the ASGI framework Starlette, and intended to emit metrics to Datadog, a statsd-based cloud monitoring service.

ASGI version

Since 0.2.0 this middleware only supports ASGI3, if you need ASGI2 support please use version 0.1.2.

installation

pip install timing-asgi

usage

Here's an example using the Starlette ASGI framework which prints out the timing metrics..

A more realistic example which emits the timing metrics to Datadog can be found at https://github.com/steinnes/timing-starlette-asgi-example.

import logging
import uvicorn

from starlette.applications import Starlette
from starlette.responses import PlainTextResponse
from timing_asgi import TimingMiddleware, TimingClient
from timing_asgi.integrations import StarletteScopeToName


class PrintTimings(TimingClient):
    def timing(self, metric_name, timing, tags):
        print(metric_name, timing, tags)


app = Starlette()


@app.route("/")
def homepage(request):
    return PlainTextResponse("hello world")


app.add_middleware(
    TimingMiddleware,
    client=PrintTimings(),
    metric_namer=StarletteScopeToName(prefix="myapp", starlette_app=app)
)

if __name__ == "__main__":
    logging.basicConfig(level=logging.INFO)
    uvicorn.run(app)

Running this example and sending some requests:

$ python app.py
INFO: Started server process [35895]
INFO: Waiting for application startup.
2019-03-07 11:38:01 INFO  [timing_asgi.middleware:44] ASGI scope of type lifespan is not supported yet
INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO: ('127.0.0.1', 58668) - "GET / HTTP/1.1" 200
myapp.__main__.homepage 0.0006690025329589844 ['http_status:200', 'http_method:GET', 'time:wall']
myapp.__main__.homepage 0.0006950000000000012 ['http_status:200', 'http_method:GET', 'time:cpu']
INFO: ('127.0.0.1', 58684) - "GET /asdf HTTP/1.1" 404
myapp.asdf 0.0005478858947753906 ['http_status:404', 'http_method:GET', 'time:wall']
myapp.asdf 0.0005909999999999804 ['http_status:404', 'http_method:GET', 'time:cpu']