feat(metrics): Make a consistent noop flush behavior (#2428)

Author: mitsuhiko

sentry_sdk/metrics.py

@@ -304,6 +304,7 @@ def _encode_metrics(flushable_buckets):
 class MetricsAggregator(object):
     ROLLUP_IN_SECONDS = 10.0
     MAX_WEIGHT = 100000
+    FLUSHER_SLEEP_TIME = 5.0
 
     def __init__(
         self,
@@ -350,7 +351,7 @@ def _flush_loop(self):
         while self._running or self._force_flush:
             self._flush()
             if self._running:
-                self._flush_event.wait(5.0)
+                self._flush_event.wait(self.FLUSHER_SLEEP_TIME)
 
     def _flush(self):
         # type: (...) -> None
@@ -442,6 +443,7 @@ def kill(self):
         self._flusher.join()
         self._flusher = None
 
+    @metrics_noop
     def flush(self):
         # type: (...) -> None
         self._force_flush = True
@@ -463,16 +465,7 @@ def _emit(
         encoded_metrics = _encode_metrics(flushable_buckets)
         metric_item = Item(payload=encoded_metrics, type="statsd")
         envelope = Envelope(items=[metric_item])
-
-        # A malfunctioning transport might create a forever loop of metric
-        # emission when it emits a metric in capture_envelope.  We still
-        # allow the capture to take place, but interior metric incr calls
-        # or similar will be disabled.  In the background thread this can
-        # never happen, but in the force flush case which happens in the
-        # foreground we might make it here unprotected.
-        with recursion_protection():
-            self._capture_func(envelope)
-
+        self._capture_func(envelope)
         return envelope
 
     def _serialize_tags(

tests/test_metrics.py

@@ -532,3 +532,35 @@ def bad_capture_envelope(*args, **kwargs):
     m = parse_metrics(envelope.items[0].payload.get_bytes())
     assert len(m) == 1
     assert m[0][1] == "counter@none"
+
+
+def test_flush_recursion_protection_background_flush(
+    sentry_init, capture_envelopes, monkeypatch
+):
+    monkeypatch.setattr(metrics.MetricsAggregator, "FLUSHER_SLEEP_TIME", 0.1)
+    sentry_init(
+        release="fun-release",
+        environment="not-fun-env",
+        _experiments={"enable_metrics": True},
+    )
+    envelopes = capture_envelopes()
+    test_client = Hub.current.client
+
+    real_capture_envelope = test_client.transport.capture_envelope
+
+    def bad_capture_envelope(*args, **kwargs):
+        metrics.incr("bad-metric")
+        return real_capture_envelope(*args, **kwargs)
+
+    monkeypatch.setattr(test_client.transport, "capture_envelope", bad_capture_envelope)
+
+    metrics.incr("counter")
+
+    # flush via sleep and flag
+    Hub.current.client.metrics_aggregator._force_flush = True
+    time.sleep(0.5)
+
+    (envelope,) = envelopes
+    m = parse_metrics(envelope.items[0].payload.get_bytes())
+    assert len(m) == 1
+    assert m[0][1] == "counter@none"