custom metrics return function memory location

[AHVG]

The entire metrics issue is implemented in another .py file and is imported when used in a flask route to check its metrics. Additionally, custom metrics were created using lambdas and these memory locations refer to them.

Below is an example.

flask_http_request_total{method="<function init.<locals>.<lambda> at 0x7f7657e81580>",path="<function init.<locals>.<lambda> at 0x7f7657e816c0>",path_without_uuid="<function init.<locals>.<lambda> at 0x7f7657e81760>",status="<function init.<locals>.<lambda> at 0x7f7657e81620>"} 0.0

[rycus86]

Hi,
Can you give an example of the code as well? Once we can reproduce it, we can see how it can be fixed, I'm not immediately sure what info lambda functions provide there.

[AHVG]

unfortunately I won't be able to send everything, just a small snippet, as the code is too big to fit here. But the idea is there, of how we are using the library. Furthermore, from what I can see, it is only the histogram that has this problem.

# metrics.py
from prometheus_flask_exporter import PrometheusMetrics
METRICS_PORT = os.environ.get('METRICS_PORT')


def init(flask_app: Flask):
    """
    Receives Flask instance to initialize metrics.
    """

    if not METRICS_PORT:
        logging.warning(f"Metrics could NOT enabled: port is missing ({METRICS_PORT})")
        return

    global prometheus_metrics
    global metrics_counter
    global metrics_histogram

    prometheus_metrics = PrometheusMetrics(flask_app, 
                                    excluded_paths=["^/static/.*$"], 
                                    export_defaults=False,
                                    path=None #disables '/metrics' route
                                    )
    metrics_counter = prometheus_metrics.counter(
        'flask_http_request_total', 
        'Total number of HTTP requests for all Flask requests.',
        labels={'method': lambda: request.method, 
                'status': lambda r: r.status_code, 
                'path': lambda: censor_uuids(request.path)})

    metrics_histogram = prometheus_metrics.histogram(
            'flask_http_request_duration_seconds', 
            'Flask HTTP request duration in seconds for all Flask requests.',
            labels={'method': lambda: request.method,
                    'status': lambda r: r.status_code, 
                    'path': lambda: censor_uuids(request.path)})

def record_metrics(func):
    """Decorator to record metrics of flask route if metrics are enabled"""

    if prometheus_metrics:
        @metrics_counter
        @metrics_histogram
        @wraps(func)
        def wrapper(*args, **kwargs):
            result = func(*args, **kwargs)
            return result
        
        return wrapper
    
    else:
        return func

# main.py
import metrics

from flask import Flask

application = Flask(...)
metrics.init(application)

@application.route('/how')
@metrics.record_metrics
def how():
    return render_template("how.html", is_logged=oidc.user_loggedin)

I understand that possibly with the information I have provided it may be difficult to find a solution, so there is no need to stress if it is a hassle.

[rycus86]

Thanks a lot! This should help reproduce it!
I'll try to have a look next week.

[AHVG]

I think I solved the problem by changing the version of prometheus-flask-exporter from 0.22.3 to 0.23.0, but I definitely don't understand why.

Thank you for the quick response and attention.