chore(cohorts): Pause cohort dependency metrics on cache warm (#39123)

Author: dustinbyrne

posthog/models/cohort/dependencies.py

@@ -40,7 +40,7 @@ def extract_cohort_dependencies(cohort: Cohort) -> set[int]:
     return dependencies
 
 
-def get_cohort_dependencies(cohort: Cohort) -> list[int]:
+def get_cohort_dependencies(cohort: Cohort, _warming: bool = False) -> list[int]:
     """
     Get the list of cohort IDs that the given cohort depends on.
     """
@@ -50,10 +50,11 @@ def get_cohort_dependencies(cohort: Cohort) -> list[int]:
     cache_hit = cache.has_key(cache_key)
 
     def compute_dependencies():
-        COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="miss").inc()
+        if not _warming:
+            COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="miss").inc()
         return list(extract_cohort_dependencies(cohort))
 
-    if cache_hit:
+    if cache_hit and not _warming:
         COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="hit").inc()
 
     result = cache.get_or_set(
@@ -114,7 +115,7 @@ def warm_team_cohort_dependency_cache(team_id: int, batch_size: int = 1000):
     for cohort in Cohort.objects.filter(team_id=team_id, deleted=False).iterator(chunk_size=batch_size):
         # Any invalidated dependencies cache is rebuilt here
         dependents_map.setdefault(_cohort_dependents_key(cohort.id), [])
-        dependencies = get_cohort_dependencies(cohort)
+        dependencies = get_cohort_dependencies(cohort, _warming=True)
         # Dependency keys aren't fully invalidated; make sure they don't expire.
         cache.touch(_cohort_dependencies_key(cohort.id), timeout=DEPENDENCY_CACHE_TIMEOUT)
         # Build reverse map

posthog/models/cohort/test/test_dependencies.py

@@ -390,3 +390,23 @@ def test_cache_hit_miss_sequence(self):
             cache_type="dependents", result="hit"
         )._value._value
         self.assertEqual(dept_hits_after_second, dept_initial_hits + 1)
+
+    def test_warming_does_not_increment_counters(self):
+        """Verify that cache warming operations don't increment the counter metrics"""
+        cohort_a = self._create_cohort(name="Test Cohort A")
+        self._create_cohort(
+            name="Test Cohort B", groups=[{"properties": [{"key": "id", "type": "cohort", "value": cohort_a.id}]}]
+        )
+
+        cache.clear()
+
+        initial_hits = COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="hit")._value._value
+        initial_misses = COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="miss")._value._value
+
+        warm_team_cohort_dependency_cache(self.team.id)
+
+        # Verify counters did not increment during warming
+        final_hits = COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="hit")._value._value
+        final_misses = COHORT_DEPENDENCY_CACHE_COUNTER.labels(cache_type="dependencies", result="miss")._value._value
+        self.assertEqual(final_hits, initial_hits)
+        self.assertEqual(final_misses, initial_misses)