fix(runtime metrics): Fix manually starting runtime metrics (#2564) (#2621)

* fix(runtime metrics): Fix manually starting runtime metrics

* Add release note

* fix release note

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit 8e1de83)

Co-authored-by: Brett Langdon <[email protected]>

Author: mergify[bot]

ddtrace/runtime/__init__.py

@@ -1,6 +1,6 @@
 from typing import Optional
 
-import ddtrace
+import ddtrace.internal.runtime.runtime_metrics
 
 
 class RuntimeMetrics(object):

releasenotes/notes/fix-manual-runtime-metrics-0873e17de485f8b0.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue when trying to manually start the runtime metrics worker::
+
+      AttributeError: module 'ddtrace.internal.runtime' has no attribute 'runtime_metrics'

tests/runtime/test_runtime_metrics_api.py

@@ -22,3 +22,24 @@ def test_runtime_metrics_api_idempotency():
     RuntimeMetrics.disable()
     assert RuntimeWorker._instance is None
     RuntimeMetrics.disable()
+
+
+def test_manually_start_runtime_metrics(run_python_code_in_subprocess):
+    """
+    When importing and manually starting runtime metrics
+        There are no errors
+    """
+    out, err, status, pid = run_python_code_in_subprocess(
+        """
+from ddtrace.runtime import RuntimeMetrics
+RuntimeMetrics.enable()
+
+from ddtrace.internal.runtime.runtime_metrics import RuntimeWorker
+assert RuntimeWorker._instance is not None
+
+RuntimeMetrics.disable()
+assert RuntimeWorker._instance is None
+""",
+    )
+
+    assert status == 0