record dropping metrics and test

Author: alexander-alderman-webb

sentry_sdk/_metrics_batcher.py

@@ -19,10 +19,12 @@ class MetricsBatcher:
     def __init__(
         self,
         capture_func,  # type: Callable[[Envelope], None]
+        record_lost_func,  # type: Callable[..., None]
     ):
         # type: (...) -> None
         self._metric_buffer = []  # type: List[Metric]
         self._capture_func = capture_func
+        self._record_lost_func = record_lost_func
         self._running = True
         self._lock = threading.Lock()
 
@@ -74,6 +76,11 @@ def add(
 
         with self._lock:
             if len(self._metric_buffer) >= self.MAX_METRICS_BEFORE_DROP:
+                self._record_lost_func(
+                    reason="queue_overflow",
+                    data_category="trace_metric",
+                    quantity=1,
+                )
                 return None
 
             self._metric_buffer.append(metric)

sentry_sdk/client.py

@@ -377,7 +377,10 @@ def _capture_envelope(envelope):
 
             self.metrics_batcher = None
             if has_metrics_enabled(self.options):
-                self.metrics_batcher = MetricsBatcher(capture_func=_capture_envelope)
+                self.metrics_batcher = MetricsBatcher(
+                    capture_func=_capture_envelope,
+                    record_lost_func=self.transport.record_lost_event,
+                )
 
             max_request_body_size = ("always", "never", "small", "medium")
             if self.options["max_request_body_size"] not in max_request_body_size:

tests/test_metrics.py

@@ -8,6 +8,8 @@
 from sentry_sdk.envelope import Envelope
 from sentry_sdk.types import Metric
 
+from sentry_sdk._metrics_batcher import MetricsBatcher
+
 
 def envelopes_to_metrics(envelopes):
     # type: (List[Envelope]) -> List[Metric]
@@ -204,3 +206,27 @@ def _before_metric(record, hint):
     assert len(metrics) == 1
     assert metrics[0]["name"] == "test.keep"
     assert before_metric_called
+
+
+def test_batcher_drops_metrics(sentry_init, monkeypatch):
+    sentry_init()
+    client = sentry_sdk.get_client()
+
+    def no_op_flush():
+        pass
+
+    monkeypatch.setattr(client.metrics_batcher, "_flush", no_op_flush)
+
+    lost_event_calls = []
+
+    def record_lost_event(reason, data_category=None, item=None, *, quantity=1):
+        lost_event_calls.append((reason, data_category, item, quantity))
+
+    monkeypatch.setattr(client.metrics_batcher, "_record_lost_func", record_lost_event)
+
+    for i in range(10_005):  # 5 metrics over the hard limit
+        sentry_sdk.metrics.count("test.counter", 1)
+
+    assert len(lost_event_calls) == 5
+    for lost_event_call in lost_event_calls:
+        assert lost_event_call == ("queue_overflow", "trace_metric", None, 1)