fastapi-telemetry 0.0.2

Prometheus metrics middleware, circuit breaker listener, and metric helpers for FastAPI — zero project-specific dependencies

fastapi-telemetry

📢 Hobby Project Notice: This is a research and learning project exploring FastAPI observability and Prometheus metrics best practices. Feel free to use it as a reference, report issues, or suggest improvements! Contributions and feedback are always welcome.

Prometheus metrics middleware, circuit breaker listener, and metric helpers for FastAPI — zero project-specific dependencies (only Starlette and prometheus-client).

Features

• PrometheusMiddleware — HTTP request duration, count, and in-flight metrics out of the box via injectable callbacks (no coupling to a specific metrics facade)
• CircuitBreakerMetricsListener — pybreaker listener that exports circuit breaker state, state-changes, and failure counts to Prometheus (optional dependency)
• get_or_create_counter / get_or_create_gauge / get_or_create_histogram — safe helpers that return an existing metric from the registry instead of raising ValueError on duplicate registration (useful with --reload)

Installation

# Core (middleware + helpers)
pip install fastapi-telemetry

# With circuit-breaker support
pip install "fastapi-telemetry[circuit-breaker]"

Quick start

from fastapi import FastAPI
from fastapi_telemetry import PrometheusMiddleware, CircuitBreakerMetricsListener
from prometheus_client import make_asgi_app

app = FastAPI()

# Mount Prometheus scrape endpoint
app.mount("/metrics", make_asgi_app())

# Wire up the middleware with your own metric callbacks
app.add_middleware(
    PrometheusMiddleware,
    request_start_callback=lambda method, path: None,   # replace with your gauge.inc()
    request_end_callback=lambda m, p, s, d: None,       # replace with your histogram
    error_callback=lambda error_type, path: None,       # replace with your counter.inc()
)

Circuit breaker

from pybreaker import CircuitBreaker
from fastapi_telemetry import CircuitBreakerMetricsListener

cb = CircuitBreaker(
    name="redis",
    listeners=[CircuitBreakerMetricsListener(service_name="redis")],
)

License

MIT