Add metrics for request/task counting

src/pretix/base/metrics.py

@@ -146,5 +146,7 @@ def metric_values():
 """
 Provided metrics
 """
-http_requests_total = Counter("http_requests_total", "Total number of HTTP requests made.", ["code", "handler", "method"])
-# usage: http_requests_total.inc(code="200", handler="/foo", method="GET")
+http_view_requests = Counter("http_view_requests", "Total number of HTTP requests made.",
+                             ["status_code", "method", "url_name"])
+celery_task_runs = Counter("celery_task_runs", "Total calls to a celery task",
+                           ["task_name", "status"])

src/pretix/base/services/async.py

@@ -15,12 +15,12 @@ import time
 from django.conf import settings
 from django.db import transaction
 
+from pretix.base.metrics import celery_task_runs
 from pretix.celery_app import app
 
 
 class ProfiledTask(app.Task):
     def __call__(self, *args, **kwargs):
-
         if settings.PROFILING_RATE > 0 and random.random() < settings.PROFILING_RATE / 100:
             profiler = cProfile.Profile()
             profiler.enable()
@@ -35,6 +35,23 @@ class ProfiledTask(app.Task):
         else:
             return super().__call__(*args, **kwargs)
 
+    def on_failure(self, exc, task_id, args, kwargs, einfo):
+        if settings.METRICS_ENABLED:
+            expected = False
+            for t in self.throws:
+                if isinstance(exc, t):
+                    expected = True
+                    break
+            celery_task_runs.inc(1, task_name=self.name, status="expected-error" if expected else "error")
+
+        return super().on_failure(exc, task_id, args, kwargs, einfo)
+
+    def on_success(self, retval, task_id, args, kwargs):
+        if settings.METRICS_ENABLED:
+            celery_task_runs.inc(1, task_name=self.name, status="success")
+
+        return super().on_success(retval, task_id, args, kwargs)
+
 
 class TransactionAwareTask(ProfiledTask):
     """