implement basic prometheus metric endpoint

Author: Roman Plevka

rekuper.py

@@ -4,10 +4,13 @@
 from flask_sqlalchemy import SQLAlchemy
 from flask_migrate import Migrate
 from flask_restx import Api, Resource, fields
+from prometheus_flask_exporter import PrometheusMetrics
 from sqlalchemy import text
 from sqlalchemy.exc import IntegrityError, SQLAlchemyError
 
 app = Flask("__name__")
+metrics = PrometheusMetrics(app)
+
 if settings.database.get("connection_string") is None:
     db_creds = f"{settings.database.username}:{settings.database.password}"
     db_host = settings.database.host
@@ -362,5 +365,15 @@ def get(self):
         return [container.to_dict() for container in containers], 200
 
 
+# register routes to the prometheus metrics
+metrics.register_default(
+    metrics.counter(
+        "by_path_counter",
+        "Request count by request paths",
+        labels={"path": lambda: request.path},
+    )
+)
+
+
 if __name__ == "__main__":
     app.run(debug=True)

requirements.txt

@@ -3,5 +3,6 @@ Flask
 Flask-SQLAlchemy
 Flask-Migrate
 flask-restx
+prometheus-flask-exporter
 psycopg2-binary
 requests