Support dynamic metric name prefixes in the metrics registry check

scripts/ci/prek/check_metrics_synced_with_the_registry.py

@@ -97,16 +97,25 @@ def normalize_metric_name(registry_metric_name: str) -> str:
     return re.sub(r"\{[^}]+\}", "*", registry_metric_name)
 
 
-# Sentinel returned when a dynamic metric name is partially matched based on a common prefix.
+# Sentinel returned when a dynamic metric name is partially matched based on its static part.
 # For dynamic metric names that include variables, the check can't find an exact match with a registry
-# entry or its type. So, a partially matched prefix is good enough and type checking is skipped.
+# entry or its type. So, a partial match is good enough and type checking is skipped.
 _PREFIX_MATCHED = "__prefix_matched__"
 
 
 def find_prefix_matched_registry_entries(metric_name: str, metrics_registry: dict[str, dict]) -> list[str]:
-    """Return the registry entry names whose name matches the static prefix of a dynamic metric name."""
+    """Return the registry entry names whose name matches the static part of a dynamic metric name.
+
+    ``{stats_prefix}.cache_hit`` has no static prefix, so it matches on its static suffix, which
+    must start with a dot to only match whole segments.
+    """
     base = metric_name.split("{")[0].rstrip(".")
-    return [name for name in metrics_registry if name == base or name.startswith(base + ".")]
+    if base:
+        return [name for name in metrics_registry if name == base or name.startswith(base + ".")]
+    suffix = metric_name.rsplit("}", 1)[-1]
+    if not suffix.startswith("."):
+        return []
+    return [name for name in metrics_registry if name.endswith(suffix)]
 
 
 def find_registry_match(metric_name: str, metrics_registry: dict[str, dict]) -> str | None:
@@ -127,11 +136,8 @@ def find_registry_match(metric_name: str, metrics_registry: dict[str, dict]) ->
 
     # Dynamic metric name.
     if "{" in metric_name and find_prefix_matched_registry_entries(metric_name, metrics_registry):
-        # Metric prefix matches the prefix of a dynamic registry entry.
-        # If the static part before the first variable, matches an exact registry entry name,
-        # or a dotted-prefix of one, then the name is considered covered and
-        # _PREFIX_MATCHED is returned. The type check must be skipped because
-        # the resulting metric name with all variables expanded, cannot be determined.
+        # The type check must be skipped because the name with all variables expanded
+        # cannot be determined.
         return _PREFIX_MATCHED
 
     # All checks for matching failed.

scripts/tests/ci/prek/test_check_metrics_synced_with_the_registry.py

@@ -119,6 +119,7 @@ def test_normalize_metric_name(metric_name, expected_result):
         pytest.param("dag.{x}.{y}.duration", "task.duration", id="legacy_name_match_different_structure"),
         pytest.param("ti.{state}", _PREFIX_MATCHED, id="prefix_match_returns_sentinel"),
         pytest.param("dagrun.duration.{state}", _PREFIX_MATCHED, id="prefix_match_dotted_base"),
+        pytest.param("{stats_prefix}.open_slots", _PREFIX_MATCHED, id="suffix_match_returns_sentinel"),
         pytest.param("non.existent.{var}", None, id="dynamic_metric_no_prefix_match_returns_none"),
         pytest.param("non.existent", None, id="static_metric_not_in_registry_returns_none"),
     ],
@@ -226,6 +227,12 @@ def test_extract_metric_names_from_ast_node(code: str, expected_result):
         ),
         pytest.param("dagrun.duration.{state}", ["dagrun.duration.success"], id="dotted_base_prefix"),
         pytest.param("non.existent.{var}", [], id="no_prefix_match_returns_empty_list"),
+        pytest.param(
+            "{stats_prefix}.open_slots",
+            ["pool.open_slots", "executor.open_slots"],
+            id="leading_variable_matches_on_static_suffix",
+        ),
+        pytest.param("{stats_prefix}pen_slots", [], id="suffix_not_starting_at_a_dot_returns_empty_list"),
     ],
 )
 def test_find_prefix_matched_registry_entries(metric_name, expected_result):
@@ -277,6 +284,18 @@ def test_find_prefix_matched_registry_entries(metric_name, expected_result):
             ],
             id="legacy_name_structure_match_marks_entry_used",
         ),
+        pytest.param(
+            {"{stats_prefix}.open_slots"},
+            [
+                "dagrun.duration.success",
+                "scheduler.heartbeat",
+                "task.duration",
+                "ti.queued",
+                "ti.scheduled",
+                "ti.start.{dag_id}.{task_id}",
+            ],
+            id="suffix_match_marks_all_matching_entries_used",
+        ),
     ],
 )
 def test_compute_unused_registry_entries(code_metric_names, expected_unused):