fix(metrics_metadata): skip distribution-typed metrics in update path

datadog_sync/model/metrics_metadata.py

@@ -54,6 +54,25 @@ async def create_resource(self, _id: str, resource: Dict) -> Tuple[str, Dict]:
     async def update_resource(self, _id: str, resource: Dict) -> Tuple[str, Dict]:
         destination_client = self.config.destination_client
 
+        # Distribution metrics cannot be written via PUT /api/v1/metrics/{name}
+        # — the destination rejects type=distribution with a 400 at the DB
+        # layer. Skip early so the run does not burn retries on a request
+        # that will never succeed. Skip fires before the destination probe
+        # below to avoid a wasted GET.
+        #
+        # Case-tolerant match: the destination canonicalizes to lowercase but
+        # normalize defensively so an upstream drift in the source-side casing
+        # cannot silently re-enable the 400 loop.
+        metric_type = (resource.get("type") or "").strip().lower()
+        if metric_type == "distribution":
+            log.debug(f"[metrics_metadata - {_id}] skipping: distribution type not writable via public PUT")
+            raise SkipResource(
+                _id,
+                self.resource_type,
+                "distribution type is rejected by the destination metrics_metadata endpoint; "
+                "skipping public PUT",
+            )
+
         # metrics_metadata can only attach to a metric that already exists on
         # destination. Legacy dogweb returns 400 {"errors":["error updating metric
         # metadata"]} when the metric is missing; that failure adds ~25-30min of

tests/unit/test_metrics_metadata.py

@@ -3,7 +3,7 @@
 # This product includes software developed at Datadog (https://www.datadoghq.com/).
 # Copyright 2019 Datadog, Inc.
 
-"""Unit tests for metrics_metadata destination-existence filter (HAMR-392 Jul8-T20)."""
+"""Unit tests for metrics_metadata update_resource filters."""
 
 import asyncio
 from types import SimpleNamespace
@@ -82,6 +82,50 @@ def test_update_resource_get_403_propagates(metrics_metadata):
     client.put.assert_not_awaited()
 
 
+@pytest.mark.parametrize(
+    "type_value",
+    ["distribution", "Distribution", "DISTRIBUTION", "distribution "],
+    ids=["lowercase", "capitalized", "uppercase", "trailing_space"],
+)
+def test_update_resource_distribution_type_raises_skip(metrics_metadata, type_value):
+    """Distribution-typed metrics skip early; no destination HTTP call is made.
+    Case + whitespace variants must all skip so an upstream drift in the source
+    canonicalization cannot silently re-enable the 400 loop.
+    """
+    client = metrics_metadata.config.destination_client
+    client.get = AsyncMock()
+    client.put = AsyncMock()
+
+    with pytest.raises(SkipResource) as exc_info:
+        asyncio.run(metrics_metadata.update_resource("some.dist.metric", {"type": type_value, "description": "x"}))
+
+    assert "some.dist.metric" in str(exc_info.value)
+    assert "distribution" in str(exc_info.value)
+    client.get.assert_not_awaited()
+    client.put.assert_not_awaited()
+
+
+@pytest.mark.parametrize("type_value", ["count", "rate", "gauge", "histogram", None])
+def test_update_resource_non_distribution_type_probes_destination(metrics_metadata, type_value):
+    """Regression: non-distribution types (and missing type) still probe destination via GET before PUT.
+    The v1 probe endpoint returns a flat metric metadata dict; the return value is unused (only
+    non-404 status matters), so any non-None dict works as a mock.
+    """
+    client = metrics_metadata.config.destination_client
+    client.get = AsyncMock(return_value={"type": type_value or "count", "description": "existing"})
+    client.put = AsyncMock(return_value={"description": "updated"})
+
+    resource = {"description": "updated"}
+    if type_value is not None:
+        resource["type"] = type_value
+
+    _id, _ = asyncio.run(metrics_metadata.update_resource("some.metric", resource))
+
+    assert _id == "some.metric"
+    client.get.assert_awaited_once()
+    client.put.assert_awaited_once()
+
+
 def test_create_resource_delegates_to_update(metrics_metadata):
     """create_resource remains a thin wrapper around update_resource (behaviour unchanged)."""
     client = metrics_metadata.config.destination_client