From 5513a8d77fcedcb81ed61f77b0041e74c4e91f0f Mon Sep 17 00:00:00 2001
From: "sentry-junior[bot]"
 <264270552+sentry-junior[bot]@users.noreply.github.com>
Date: Fri, 23 Oct 2026 14:19:12 +0000
Subject: [PATCH] fix(fetcher): Handle missing unit in Datadog query responses

Datadog's v1 query API now omits series[].unit for metrics without unit metadata, which made warn_multiple_units raise KeyError and fail every run.

Refs PRODENG-2990

Co-Authored-By: Bojan Oro <bojan.oro@sentry.io>
---
 py/tests/test_fetcher.py              | 19 +++++++++++++++++++
 py/usageaccountant/datadog_fetcher.py |  5 +++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/py/tests/test_fetcher.py b/py/tests/test_fetcher.py
index 73564c3..6d949ed 100644
--- a/py/tests/test_fetcher.py
+++ b/py/tests/test_fetcher.py
@@ -131,6 +131,25 @@ def test_warn_multiple_units(self) -> None:
             )
             assert len(cm.output) == 1
 
+    def test_warn_multiple_units_no_unit(self) -> None:
+        """
+        Datadog omits `unit` for metrics without unit metadata.
+        """
+        series_list = self.good_response["series"]
+        series_list[0].pop("unit")  # type: ignore
+        with self.assertNoLogs("fetcher"):
+            ddf.warn_multiple_units(
+                cast(Sequence[ddf.DatadogResponseSeries], series_list)
+            )
+
+    def test_warn_multiple_units_single_unit(self) -> None:
+        series_list = self.good_response["series"]
+        series_list[0]["unit"] = [{"plural": "bytes"}]  # type: ignore
+        with self.assertNoLogs("fetcher"):
+            ddf.warn_multiple_units(
+                cast(Sequence[ddf.DatadogResponseSeries], series_list)
+            )
+
     def test_warn_multiple_units_empty_series(self) -> None:
         """
         Test that warn_multiple_units handles empty series list gracefully.
diff --git a/py/usageaccountant/datadog_fetcher.py b/py/usageaccountant/datadog_fetcher.py
index 6400f64..4d2a932 100644
--- a/py/usageaccountant/datadog_fetcher.py
+++ b/py/usageaccountant/datadog_fetcher.py
@@ -174,8 +174,9 @@ def warn_multiple_units(series_list: Sequence[DatadogResponseSeries]) -> None:
     if not series_list:
         return
 
-    unit_list = series_list[0]["unit"]
-    if unit_list and unit_list[1] is not None:
+    # Datadog omits `unit` entirely for metrics without unit metadata.
+    unit_list = series_list[0].get("unit")
+    if unit_list and len(unit_list) > 1 and unit_list[1] is not None:
         logger.warning(f"Received multiple units from Datadog: {unit_list}.")