fix(metrics): Ensure task_sent counters are not instantiated

Author: adinhodovic

src/exporter.py

@@ -301,10 +301,10 @@ def track_task_event(self, event):
                 logger.debug(
                     "Incremented metric='{}' labels='{}'", counter._name, labels
                 )
-            elif (
-                event["type"] != "task-sent"
-            ):  # task-sent is sent by various hosts (webservers, task creators etc.) which cause label cardinality # pylint: disable=line-too-long
-                # increase unaffected counters by zero in order to make them visible
+            elif counter_name != "task-sent":
+                # instantiate unaffected counters by zero in order to make them visible
+                # task-sent is sent by various hosts (webservers, task creators)
+                # this causes label cardinality, therefore we do not want to instantiate the counter
                 counter.labels(**_labels).inc(0)
 
         # observe task runtime

src/test_metrics.py

@@ -196,7 +196,7 @@ def test_purge_offline_worker_metrics(
     )
 
 
-def test_worker_generic_task_sent_hostname(threaded_exporter, celery_app):
+def test_worker_generic_task_sent_hostname(threaded_exporter, celery_app, hostname):
     threaded_exporter.generic_hostname_task_sent_metric = True
     time.sleep(5)
 
@@ -219,3 +219,15 @@ def succeed():
             )
             == 1.0
         )
+
+        assert (
+            threaded_exporter.registry.get_sample_value(
+                "celery_task_sent_total",
+                labels={
+                    "hostname": hostname,
+                    "name": "src.test_metrics.succeed",
+                    "queue_name": "celery",
+                },
+            )
+            is None
+        )