Add "invocation_started_at" global field (#246)

* Add invocation_started_at

* Changie

* Add unit test

.changes/unreleased/Features-20250213-135245.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Add "invocation_started_at" global field
+time: 2025-02-13T13:52:45.156677-05:00
+custom:
+  Author: gshank
+  Issue: "245"

dbt_common/invocation.py

@@ -1,12 +1,19 @@
 import uuid
+from datetime import datetime
 
 _INVOCATION_ID = str(uuid.uuid4())
+_INVOCATION_STARTED_AT = datetime.utcnow()
 
 
 def get_invocation_id() -> str:
     return _INVOCATION_ID
 
 
+def get_invocation_started_at() -> datetime:
+    return _INVOCATION_STARTED_AT
+
+
 def reset_invocation_id() -> None:
-    global _INVOCATION_ID
+    global _INVOCATION_ID, _INVOCATION_STARTED_AT
     _INVOCATION_ID = str(uuid.uuid4())
+    _INVOCATION_STARTED_AT = datetime.utcnow()

tests/unit/test_invocation.py

@@ -0,0 +1,12 @@
+from dbt_common.invocation import get_invocation_id, get_invocation_started_at, reset_invocation_id
+
+
+def test_invocation_started_at():
+    inv_id = get_invocation_id()
+    assert inv_id
+    inv_start = get_invocation_started_at()
+    assert inv_start
+
+    reset_invocation_id()
+    inv_start != get_invocation_started_at()
+    inv_id != get_invocation_id()