monitor, trace, and collect metrics

How to

• Start metrics services (e.g., Prometheus) from lifespan and update counters during runtime.

Example

from prometheus_client import start_http_server, Counter

metrics_counter = Counter('app_start', 'App has started')

async def lifespan(app):
    start_http_server(9000)  # separate metrics port
    metrics_counter.inc()
    yield

References

• http/lifespan.md:1