Share `metrics` object across modules

Hello, my API is spread across several Blueprints and namespaces while the metrics object gets instantiated in my main app.py. Is there a built-in way to share the object across modules, maybe something like current_app in Flask?

app.py

import api.internal
import api.external

app = Flask(__name__)
metrics = GunicornPrometheusMetrics(app)

I have seen the app factory example, but there everything is set up in its own app_setup.py. But I cannot import app.py in my APIs as this would introduce circular dependencies.

Am I missing something (as a beginner) or should I just create a “singleton” method somewhere?

metrics = None

def get_current_metrics(app):
    global metrics

    if metrics is None and app:
        metrics = GunicornPrometheusMetrics(app)
        
    return metrics

Thanks in advance

[salapat11]

I see the issue now. I had the decorator at the class level instead of the method level. It works as expected. Thanks again for your time @rycus86 , @trallnag .

Thanks for putting this library, @rycus86 . Very easy to integrate and got it working in few mins.

[trallnag]

@salapat11, create a file telemetry.py (or use the __init__.py, whatever) where you use the app factory pattern just like @rycus86 recommended.

from prometheus_flask_exporter import PrometheusMetrics
METRICS = PrometheusMetrics.for_app_factory()

In your module where you create the “root” Flask object:

from telemetry import METRICS
# ...
METRICS.init_app(flask_app)

In all other modules where you want to use the metrics object:

from telemetry import METRICS