Duplicated timeseries in CollectorRegistry with Multiprocess Gunicorn

I know this is a subject that comes up somewhat frequently but for the love of me I can't figure out what I'm doing wrong.

1. I have a service in Amazon ECS thats running a single task with multiple workers (actually the problem happens in my other service that just has one worker also).

2. I've created the directory and set the PROMETHEUS_MULTIPROC_DIR in the Dockerfile:

RUN mkdir -p /tmp/prom-metrics
ENV PROMETHEUS_MULTIPROC_DIR /tmp/prom-metrics

3. I'm using the sample code in the README to create the registry in the /metrics request and return it:

registry = CollectorRegistry()
if getenv('PROMETHEUS_MULTIPROC_DIR'):
  multiprocess.MultiProcessCollector(registry)
data = generate_latest(registry)
status = '200 OK'
response_headers = [
    ('Content-type', CONTENT_TYPE_LATEST),
    ('Content-Length', str(len(data))),
]
return Response(data, status, response_headers)

4. I've created the gunicorn.conf.py file with the sample from the README and passed it into my gunicorn startup script via -c:

from prometheus_client import multiprocess

def child_exit(server, worker):
    multiprocess.mark_process_dead(worker.pid)

In my two services, gunicorn starts them as follows:

# app 1 with workers
gunicorn -c /app/utils/gunicorn.conf.py -b :5000 -t 3600 --keep-alive 60 --threads 8 --workers 3 app:app

# app 2 without workers
gunicorn -c /app/utils/gunicorn.conf.py -b :5000 -t 3600 --keep-alive 60 --threads 8 app:app

The service boots successfully and accepts some metrics which are definitely collected in multiprocess mode, seeing as the HELP line simply displays Multiprocess metric.

This works for a few calls but eventually I get the dreaded Duplicated timeseries in CollectorRegistry error and no additional metrics are populated.

What might I be doing wrong?

Bắt đầu với ví dụ về metrics multiprocess trong README và cấu hình gunicorn.conf.py được tham chiếu, sau đó tái hiện lỗi bằng các thiết lập trong Dockerfile và các lệnh Gunicorn được hiển thị. Công việc được xem là hoàn tất khi xác định được nguyên nhân của lỗi timeseries trùng lặp và ghi lại hoặc sửa cấu hình để /metrics tiếp tục trả về metrics.