Prometheus Flask exporter with __main__

Question

I want to use Prometheus Flask exporter with __main__.

This works fine by running env FLASK_APP=app.py flask run --port=80 --host='0.0.0.0':

from flask import Flask
from prometheus_flask_exporter import PrometheusMetrics

app = Flask(__name__)
metrics = PrometheusMetrics(app)

app.debug = True

@app.route("/", methods=['GET'])
def index():
    return "hello world"

But I want to use my app in __main__, running python app.py.

from flask import Flask
from prometheus_flask_exporter import PrometheusMetrics

app = Flask(__name__)
metrics = PrometheusMetrics(app=None, path='/metrics')

app.debug = True

@app.route("/", methods=['GET'])
def index():
    return "hello world"

if __name__ == '__main__':
    metrics.init_app(app)
    app.run(host='0.0.0.0', port=80)

Here I get 400 on /metrics.

I got no clue how to init metrics correctly.

Answer 1

I got help on gitlab from maintainer rycus86

You have to set env DEBUG_METRICS on any value (true/false). It just must not be empty.

export DEBUG_METRICS=false