closes #3104 - add support for exposing prometheus metrics

netbox/extras/apps.py

@@ -7,6 +7,9 @@ class ExtrasConfig(AppConfig):
     name = "extras"
 
     def ready(self):
+
+        import extras.signals
+
         # Check that we can connect to the configured Redis database if webhooks are enabled.
         if settings.WEBHOOKS_ENABLED:
             try:

netbox/extras/middleware.py

@@ -7,6 +7,7 @@ from django.conf import settings
 from django.db.models.signals import post_delete, post_save
 from django.utils import timezone
 from django.utils.functional import curry
+from django_prometheus.models import model_deletes, model_inserts, model_updates
 
 from extras.webhooks import enqueue_webhooks
 from .constants import (
@@ -37,15 +38,20 @@ def _record_object_deleted(request, instance, **kwargs):
     if hasattr(instance, 'log_change'):
         instance.log_change(request.user, request.id, OBJECTCHANGE_ACTION_DELETE)
 
+    # Enqueue webhooks
     enqueue_webhooks(instance, request.user, request.id, OBJECTCHANGE_ACTION_DELETE)
 
+    # Increment metric counters
+    model_deletes.labels(instance._meta.model_name).inc()
+
 
 class ObjectChangeMiddleware(object):
     """
-    This middleware performs two functions in response to an object being created, updated, or deleted:
+    This middleware performs three functions in response to an object being created, updated, or deleted:
 
         1. Create an ObjectChange to reflect the modification to the object in the changelog.
         2. Enqueue any relevant webhooks.
+        3. Increment metric counter for the event type
 
     The post_save and pre_delete signals are employed to catch object modifications, however changes are recorded a bit
     differently for each. Objects being saved are cached into thread-local storage for action *after* the response has
@@ -85,6 +91,12 @@ class ObjectChangeMiddleware(object):
             # Enqueue webhooks
             enqueue_webhooks(obj, request.user, request.id, action)
 
+            # Increment metric counters
+            if action == OBJECTCHANGE_ACTION_CREATE:
+                model_inserts.labels(obj._meta.model_name).inc()
+            elif action == OBJECTCHANGE_ACTION_UPDATE:
+                model_updates.labels(obj._meta.model_name).inc()
+
         # Housekeeping: 1% chance of clearing out expired ObjectChanges
         if _thread_locals.changed_objects and settings.CHANGELOG_RETENTION and random.randint(1, 100) == 1:
             cutoff = timezone.now() - timedelta(days=settings.CHANGELOG_RETENTION)

netbox/extras/signals.py

@@ -0,0 +1,22 @@
+from cacheops.signals import cache_invalidated, cache_read
+from prometheus_client import Counter
+
+
+cacheops_cache_hit = Counter('cacheops_cache_hit', 'Number of cache hits')
+cacheops_cache_miss = Counter('cacheops_cache_miss', 'Number of cache misses')
+cacheops_cache_invalidated = Counter('cacheops_cache_invalidated', 'Number of cache invalidations')
+
+
+def cache_read_collector(sender, func, hit, **kwargs):
+    if hit:
+        cacheops_cache_hit.inc()
+    else:
+        cacheops_cache_miss.inc()
+
+
+def cache_invalidated_collector(sender, obj_dict, **kwargs):
+    cacheops_cache_invalidated.inc()
+
+
+cache_read.connect(cache_read_collector)
+cache_invalidated.connect(cache_invalidated_collector)