Gauge

from flask import Flask, request
from prometheus_client import Gauge
import time

app = Flask(__name__)

# Create a Gauge with labels for HTTP method and path.
# Label order here must match the values passed to labels().
IN_PROGRESS = Gauge(
    'inprogress_requests',
    'Total number of requests in progress',
    labelnames=['method', 'path']
)

@app.before_request
def before_request():
    # Increment when a request starts
    IN_PROGRESS.labels(request.method, request.path).inc()
    request.start_time = time.time()

@app.after_request
def after_request(response):
    # Decrement when the request finishes
    IN_PROGRESS.labels(request.method, request.path).dec()
    return response

# To ensure decrement even on exceptions, see teardown example below

@app.before_request
def before_request():
    IN_PROGRESS.labels(request.method, request.path).inc()

@app.teardown_request
def teardown_request(exc):
    # This runs even if an exception occurred
    IN_PROGRESS.labels(request.method, request.path).dec()

inprogress_requests{method="GET",path="/cars"} 3.0
inprogress_requests{method="POST",path="/cars"} 0.0
inprogress_requests{method="POST",path="/boats"} 18.0
inprogress_requests{method="GET",path="/boats"} 7.0