fix(runtime): set default interval when enabling (#2613) (#2620)

* fix(runtime): set default interval when enabling

* address feedback

* handle edge case and better naming

* remove comment

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit 77946b2)

Co-authored-by: Tahir H. Butt <tahir.butt@datadoghq.com>

ddtrace/internal/runtime/runtime_metrics.py

@@ -62,15 +62,17 @@ class RuntimeMetrics(RuntimeCollectorsIterable):
     ]
 
 
+def _get_interval_or_default():
+    return float(get_env("runtime_metrics", "interval", default=10))
+
+
 @attr.s(eq=False)
 class RuntimeWorker(periodic.PeriodicService):
     """Worker thread for collecting and writing runtime metrics to a DogStatsd
     client.
     """
 
-    _interval = attr.ib(
-        type=float, factory=lambda: float(get_env("runtime_metrics", "interval", default=10))  # type: ignore[arg-type]
-    )
+    _interval = attr.ib(type=float, factory=_get_interval_or_default)
     tracer = attr.ib(type=ddtrace.Tracer, default=None)
     dogstatsd_url = attr.ib(type=Optional[str], default=None)
     _dogstatsd_client = attr.ib(init=False, repr=False)
@@ -122,6 +124,8 @@ def enable(cls, flush_interval=None, tracer=None, dogstatsd_url=None):
         with cls._lock:
             if cls._instance is not None:
                 return
+            if flush_interval is None:
+                flush_interval = _get_interval_or_default()
             runtime_worker = cls(flush_interval, tracer, dogstatsd_url)  # type: ignore[arg-type]
             runtime_worker.start()
             # force an immediate update constant tags

releasenotes/notes/fix-runtime-default-interval-e3afb49f45296877.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes an issue with enabling the runtime worker introduced in v0.49.0 where no runtime metrics were sent to the agent.

tests/runtime/test_runtime_metrics_api.py

@@ -1,6 +1,9 @@
+import pytest
+
 from ddtrace.internal.runtime.runtime_metrics import RuntimeWorker
 from ddtrace.internal.service import ServiceStatus
 from ddtrace.runtime import RuntimeMetrics
+from tests.utils import DummyTracer
 
 
 def test_runtime_metrics_api():
@@ -83,3 +86,63 @@ def test_runtime_metrics_via_env_var_manual_start(monkeypatch, ddtrace_run_pytho
 """,
     )
     assert status == 0
+
+
+@pytest.mark.parametrize(
+    "enable_kwargs",
+    (
+        dict(),
+        dict(tracer=DummyTracer(), dogstatsd_url="udp://agent:8125"),
+        dict(tracer=DummyTracer(), dogstatsd_url="udp://agent:8125", flush_interval=100.0),
+        dict(flush_interval=0),
+    ),
+)
+def test_runtime_metrics_enable(enable_kwargs):
+    try:
+        RuntimeMetrics.enable(**enable_kwargs)
+
+        assert RuntimeWorker._instance is not None
+        assert RuntimeWorker._instance.status == ServiceStatus.RUNNING
+        assert (
+            RuntimeWorker._instance.tracer == enable_kwargs["tracer"]
+            if "tracer" in enable_kwargs
+            else RuntimeWorker._instance.tracer is not None
+        )
+        assert (
+            RuntimeWorker._instance.dogstatsd_url == enable_kwargs["dogstatsd_url"]
+            if "dogstatsd_url" in enable_kwargs
+            else RuntimeWorker._instance.dogstatsd_url is None
+        )
+        assert (
+            RuntimeWorker._instance.interval == enable_kwargs["flush_interval"]
+            if "flush_interval" in enable_kwargs
+            else RuntimeWorker._instance.interval == 10.0
+        )
+    finally:
+        RuntimeMetrics.disable()
+
+
+@pytest.mark.parametrize(
+    "environ",
+    (
+        dict(),
+        dict(DD_RUNTIME_METRICS_INTERVAL="0.0"),
+        dict(DD_RUNTIME_METRICS_INTERVAL="100.0"),
+    ),
+)
+def test_runtime_metrics_enable_environ(monkeypatch, environ):
+    try:
+        for (k, v) in environ.items():
+            monkeypatch.setenv(k, v)
+
+        RuntimeMetrics.enable()
+
+        assert RuntimeWorker._instance is not None
+        assert RuntimeWorker._instance.status == ServiceStatus.RUNNING
+        assert (
+            RuntimeWorker._instance.interval == float(environ["DD_RUNTIME_METRICS_INTERVAL"])
+            if "DD_RUNTIME_METRICS_INTERVAL" in environ
+            else RuntimeWorker._instance.interval == 10.0
+        )
+    finally:
+        RuntimeMetrics.disable()