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集成Prometheus

前言​

FastAPI 集成 Prometheus，通过 prometheus_client 暴露指标端点，供 Prometheus 定期拉取。

安装依赖​

python -m pip install fastapi uvicorn prometheus_client

示例​

from random import randint

import uvicorn
from fastapi import FastAPI
from fastapi.responses import PlainTextResponse
from prometheus_client import Counter, Gauge, Histogram, REGISTRY, generate_latest

app = FastAPI()

request_counter = Counter(
    "http_requests_total",
    "Total HTTP Requests",
    ["method", "path", "status"]
)
request_duration = Histogram(
    'http_request_duration_seconds',
    'HTTP Request Duration',
    ['method', 'path'])

random_gauge = Gauge(
    "http_current_users_number",
    "Current Users Number",
)


@app.get('/')
async def read_root():
    request_counter.labels(method="GET", path="/", status=200).inc()
    # random_gauge.inc(randint(1,10))  # 增值
    # random_gauge.dec(randint(1,10))  # 减值
    random_gauge.set(randint(1, 10))
    return {"msg": "Hello World"}


@app.get('/metrics')
async def get_metrics():
    return PlainTextResponse(status_code=200, content=generate_latest(REGISTRY))


if __name__ == '__main__':
    uvicorn.run(app, host='127.0.0.1', port=8000)

请求 /metrics 结果示例：

# HELP python_gc_objects_collected_total Objects collected during gc
# TYPE python_gc_objects_collected_total counter
python_gc_objects_collected_total{generation="0"} 2524.0
python_gc_objects_collected_total{generation="1"} 7725.0
python_gc_objects_collected_total{generation="2"} 2696.0
# HELP http_requests_total Total HTTP Requests
# TYPE http_requests_total counter
http_requests_total{method="GET",path="/",status="200"} 13.0
# HELP http_request_duration_seconds HTTP Request Duration
# TYPE http_request_duration_seconds histogram
# HELP http_current_users_number Current Users Number
# TYPE http_current_users_number gauge
http_current_users_number 8.0

说明​

  • Counter：只增不减的计数器，适合请求数、错误数。
  • Histogram：分布统计，适合耗时（可计算 P50/P99）。
  • Gauge：可增可减的瞬时值，适合当前在线用户数等。
  • /metrics 端点建议通过中间件自动记录每个请求的 method/path/status 与耗时，而不是在每个路由里手动埋点；生产环境注意不要把 /metrics 暴露到公网。

参考​