Subclass django_prometheus middleware to capture REST API metrics

netbox/netbox/metrics.py

@@ -0,0 +1,32 @@
+from django_prometheus.conf import NAMESPACE
+from django_prometheus import middleware
+from prometheus_client import Counter
+
+__all__ = (
+    'Metrics',
+)
+
+
+class Metrics(middleware.Metrics):
+    """
+    Expand the stock Metrics class from django_prometheus to add our own counters.
+    """
+
+    def register(self):
+        super().register()
+
+        # REST API metrics
+        self.rest_api_requests = self.register_metric(
+            Counter,
+            "rest_api_requests_total_by_method",
+            "Count of total REST API requests by method",
+            ["method"],
+            namespace=NAMESPACE,
+        )
+        self.rest_api_requests_by_view_method = self.register_metric(
+            Counter,
+            "django_http_requests_total_by_view_method",
+            "Count of REST API requests by view & method",
+            ["view", "method"],
+            namespace=NAMESPACE,
+        )

netbox/netbox/middleware.py

@@ -8,8 +8,10 @@ from django.core.exceptions import ImproperlyConfigured
 from django.db import connection, ProgrammingError
 from django.db.utils import InternalError
 from django.http import Http404, HttpResponseRedirect
+from django_prometheus import middleware
 
 from netbox.config import clear_config, get_config
+from netbox.metrics import Metrics
 from netbox.views import handler_500
 from utilities.api import is_api_request
 from utilities.error_handlers import handle_rest_api_exception
@@ -18,6 +20,8 @@ from utilities.request import apply_request_processors
 __all__ = (
     'CoreMiddleware',
     'MaintenanceModeMiddleware',
+    'PrometheusAfterMiddleware',
+    'PrometheusBeforeMiddleware',
     'RemoteUserMiddleware',
 )
 
@@ -180,6 +184,26 @@ class RemoteUserMiddleware(RemoteUserMiddleware_):
         return groups
 
 
+class PrometheusBeforeMiddleware(middleware.PrometheusBeforeMiddleware):
+    metrics_cls = Metrics
+
+
+class PrometheusAfterMiddleware(middleware.PrometheusAfterMiddleware):
+    metrics_cls = Metrics
+
+    def process_response(self, request, response):
+        response = super().process_response(request, response)
+
+        # Increment REST API request counters
+        if is_api_request(request):
+            method = self._method(request)
+            name = self._get_view_name(request)
+            self.label_metric(self.metrics.rest_api_requests, request, method=method).inc()
+            self.label_metric(self.metrics.rest_api_requests_by_view_method, request, method=method, view=name).inc()
+
+        return response
+
+
 class MaintenanceModeMiddleware:
     """
     Middleware that checks if the application is in maintenance mode

netbox/netbox/settings.py

@@ -471,9 +471,9 @@ if DEBUG:
 if METRICS_ENABLED:
     # If metrics are enabled, add the before & after Prometheus middleware
     MIDDLEWARE = [
-        'django_prometheus.middleware.PrometheusBeforeMiddleware',
+        'netbox.middleware.PrometheusBeforeMiddleware',
         *MIDDLEWARE,
-        'django_prometheus.middleware.PrometheusAfterMiddleware',
+        'netbox.middleware.PrometheusAfterMiddleware',
     ]
 
 # URLs