Fix --purge-offline-worker-metrics

src/exporter.py

@@ -322,9 +322,11 @@ def track_worker_status(self, event, is_online):
         event_name = "worker-online" if is_online else "worker-offline"
         hostname = get_hostname(event["hostname"])
         logger.debug("Received event='{}' for hostname='{}'", event_name, hostname)
-        self.celery_worker_up.labels(hostname=hostname, **self.static_label).set(value)
 
         if is_online:
+            self.celery_worker_up.labels(hostname=hostname, **self.static_label).set(
+                value
+            )
             self.worker_last_seen[hostname] = {
                 "ts": reverse_adjust_timestamp(
                     event["timestamp"], event.get("utcoffset")

src/test_metrics.py

@@ -5,7 +5,7 @@
 from celery.contrib.testing.worker import start_worker  # type: ignore
 from celery.utils.time import adjust_timestamp  # type: ignore
 
-from src.exporter import reverse_adjust_timestamp
+from src.exporter import Exporter, reverse_adjust_timestamp
 
 
 @pytest.fixture
@@ -196,6 +196,32 @@ def test_purge_offline_worker_metrics(
     )
 
 
+def test_worker_offline_event_does_not_recreate_purged_metric(hostname):
+    exporter = Exporter()
+    exporter.track_worker_status(
+        {"hostname": hostname, "timestamp": time.time(), "utcoffset": 0}, True
+    )
+    exporter.purge_worker_metrics(hostname)
+
+    assert (
+        exporter.registry.get_sample_value(
+            "celery_worker_up", labels={"hostname": hostname}
+        )
+        is None
+    )
+
+    exporter.track_worker_status(
+        {"hostname": hostname, "timestamp": time.time(), "utcoffset": 0}, False
+    )
+
+    assert (
+        exporter.registry.get_sample_value(
+            "celery_worker_up", labels={"hostname": hostname}
+        )
+        is None
+    )
+
+
 def test_worker_generic_task_sent_hostname(threaded_exporter, celery_app, hostname):
     threaded_exporter.generic_hostname_task_sent_metric = True
     time.sleep(5)