python-prometheus-0-25-0 - SKILL.md Agent Skill

name: python-prometheus-0-25-0 description: Official Prometheus Python client library v0.25.0 for instrumenting Python applications with metrics. Provides Counter, Gauge, Summary, Histogram, Info, and Enum metric types; HTTP/WSGI/ASGI exporters; framework integrations (Flask, Django, FastAPI, AIOHTTP, Twisted); Pushgateway support; multiprocess mode for Gunicorn; custom collectors; and Graphite bridge. Use when adding Prometheus metrics to Python applications, exposing metrics endpoints, or integrating with web frameworks.

Prometheus Python Client 0.25.0

Overview

The official Prometheus client library for Python. Instrument applications with metrics that Prometheus scrapes via HTTP. Six metric types cover counting, gauging, distribution tracking, and metadata exposition. The library provides built-in HTTP servers, WSGI/ASGI adapters, and framework-specific integrations for serving metrics at /metrics.

When to Use

Adding Prometheus metrics to a Python application
Exposing metrics endpoints in Flask, Django, FastAPI, AIOHTTP, or Twisted
Instrumenting request latency, error rates, queue depths, or custom business metrics
Running batch jobs that push metrics via Pushgateway
Multiprocess deployments with Gunicorn workers
Building custom collectors for external data sources

Core Concepts

Metric types — Choose based on what the value does:

Type	Update model	Use for
Counter	only up	requests served, errors, bytes sent
Gauge	up and down	queue depth, active connections, temperature
Histogram	observations in buckets	latency/size distributions with quantile queries
Summary	observations (count + sum)	latency/size when average is enough
Info	static key-value pairs	build version, environment metadata
Enum	one of N states	task state, lifecycle phase

Naming — namespace, subsystem, and name join with underscores: myapp_http_requests_total. Full metric names must match [a-zA-Z_:][a-zA-Z0-9_:]*.

Labels — Dimensions for grouping related time series. Declared via labelnames=['method', 'status'], applied via .labels(method='GET', status='200').

Registry — REGISTRY is the global default. All metric constructors register with it automatically. Pass registry=None to skip registration (useful in tests).

Installation / Setup

pip install prometheus-client

Usage Examples

Quick start with Summary decorator

from prometheus_client import start_http_server, Summary
import random, time

REQUEST_TIME = Summary('request_processing_seconds', 'Time spent processing request')

@REQUEST_TIME.time()
def process_request(t):
    time.sleep(t)

if __name__ == '__main__':
    start_http_server(8000)
    while True:
        process_request(random.random())

Visit http://localhost:8000/metrics to view metrics. Prometheus rate() function computes both requests per second and latency from the _count and _sum series.

Counter with labels

from prometheus_client import Counter, start_http_server

REQUESTS = Counter(
    'requests_total',
    'Total HTTP requests received',
    labelnames=['method', 'status'],
    namespace='myapp',
)

def handle_request(method, status):
    REQUESTS.labels(method=method, status=status).inc()

if __name__ == '__main__':
    start_http_server(8000)

Gauge tracking in-progress requests

from prometheus_client import Gauge, start_http_server

ACTIVE = Gauge('inprogress_requests', 'Number of requests being processed', namespace='myapp')

@ACTIVE.track_inprogress()
def process():
    # ... work ...
    pass

if __name__ == '__main__':
    start_http_server(8000)

Histogram with custom buckets

from prometheus_client import Histogram, start_http_server

LATENCY = Histogram(
    'request_duration_seconds',
    'HTTP request latency',
    labelnames=['method', 'endpoint'],
    namespace='myapp',
    buckets=[.01, .05, .1, .25, .5, 1, 2.5, 5],
)

def handle_request(method, endpoint):
    with LATENCY.labels(method=method, endpoint=endpoint).time():
        # ... handle request ...
        pass

if __name__ == '__main__':
    start_http_server(8000)

Advanced Topics

Metric Types: Complete reference for all 6 metric types with constructors, methods, and real-world examples → Metric Types

Labels and Exemplars: Label declaration, initialization, management, and trace-context exemplars → Labels and Exemplars

Exporting: HTTP servers, WSGI/ASGI adapters, framework integrations (Flask, Django, FastAPI, AIOHTTP, Twisted), Pushgateway, textfile collector, Graphite bridge → Exporting

Advanced Patterns: Registry management, custom collectors, multiprocess mode for Gunicorn, metrics parser, restricted registries → Advanced Patterns