Prometheus how to expose metrics in multiprocess app with start_http_server

Question

How expose metrics in multiprocess app use start_http_server

I found many examples with gunicorn in internet but i want use start_http_server

what should i do with code below to make it work properly?

from multiprocessing import Process
import time, os
from prometheus_client import start_http_server, multiprocess, CollectorRegistry, Counter


MY_COUNTER = Counter('my_counter', 'Description of my counter')
os.environ["PROMETHEUS_MULTIPROC_DIR"] = "tmp"

def f():
    print("+1")
    MY_COUNTER.inc()

if __name__ == '__main__':
    start_http_server(8000)
    p = Process(target=f, args=())
    a = p.start()
    p2 = Process(target=f, args=())
    p2.start()
    time.sleep(1)
    print("collect")
    registry = CollectorRegistry()
    data = multiprocess.MultiProcessCollector(registry)
    while True:
        time.sleep(1)

Answer 1

I was figuring out the same thing, and the solution was as simple as you would imagine.

Updated your example code to work:

from multiprocessing import Process
import shutil
import time, os
from prometheus_client import start_http_server, multiprocess, CollectorRegistry, Counter


COUNTER1 = Counter('counter1', 'Incremented by the first child process')
COUNTER2 = Counter('counter2', 'Incremented by the second child process')
COUNTER3 = Counter('counter3', 'Incremented by both child processes')


def f1():
    while True:
        time.sleep(1)
        print("Child process 1")
        COUNTER1.inc()
        COUNTER3.inc()
    

def f2():
    while True:
        time.sleep(1)
        print("Child process 2")
        COUNTER2.inc()
        COUNTER3.inc()


if __name__ == '__main__':
    # ensure variable exists, and ensure defined folder is clean on start
    prome_stats = os.environ["PROMETHEUS_MULTIPROC_DIR"]
    if os.path.exists(prome_stats):
        shutil.rmtree(prome_stats)
    os.mkdir(prome_stats)

    # pass the registry to server
    registry = CollectorRegistry()
    multiprocess.MultiProcessCollector(registry)
    start_http_server(8000, registry=registry)

    p = Process(target=f1, args=())
    a = p.start()
    p2 = Process(target=f2, args=())
    p2.start()

    print("collect")

    while True:
        time.sleep(1)

localhost:8000/metrics
# HELP counter1_total Incremented by the first child process
# TYPE counter1_total counter
counter1_total 9.0
# HELP counter2_total Incremented by the second child process
# TYPE counter2_total counter
counter2_total 9.0
# HELP counter3_total Incremented by both child processes
# TYPE counter3_total counter
counter3_total 18.0