During eviction, set is_replaying and raise special exception (#524)

Fixes #523

.github/workflows/ci.yml

@@ -105,4 +105,3 @@ jobs:
       python-repo-path: ${{github.event.pull_request.head.repo.full_name}}
       version: ${{github.event.pull_request.head.ref}}
       version-is-repo-ref: true
-      features-repo-ref: http-connect-proxy-python

temporalio/worker/_workflow_instance.py

@@ -637,6 +637,9 @@ def _apply_remove_from_cache(
     ) -> None:
         self._deleting = True
         self._cancel_requested = True
+        # We consider eviction to be under replay so that certain code like
+        # logging that avoids replaying doesn't run during eviction either
+        self._is_replaying = True
         # Cancel everything
         for task in self._tasks:
             task.cancel()
@@ -1514,7 +1517,9 @@ def _assert_not_read_only(
         self, action_attempted: str, *, allow_during_delete: bool = False
     ) -> None:
         if self._deleting and not allow_during_delete:
-            raise RuntimeError(f"Ignoring {action_attempted} while deleting")
+            raise _WorkflowBeingEvictedError(
+                f"Ignoring {action_attempted} while evicting workflow. This is not an error."
+            )
         if self._read_only:
             raise temporalio.workflow.ReadOnlyContextError(
                 f"While in read-only function, action attempted: {action_attempted}"
@@ -2614,3 +2619,7 @@ def set(
     ) -> None:
         if not temporalio.workflow.unsafe.is_replaying():
             self._underlying.set(value, additional_attributes)
+
+
+class _WorkflowBeingEvictedError(BaseException):
+    pass

tests/worker/test_workflow.py

@@ -3429,6 +3429,52 @@ async def signal_count() -> int:
         assert not hook_calls
 
 
+@dataclass
+class CapturedEvictionException:
+    is_replaying: bool
+    exception: BaseException
+
+
+captured_eviction_exceptions: List[CapturedEvictionException] = []
+
+
+@workflow.defn(sandboxed=False)
+class EvictionCaptureExceptionWorkflow:
+    @workflow.run
+    async def run(self) -> None:
+        # Going to sleep so we can force eviction
+        try:
+            await asyncio.sleep(0.01)
+        except BaseException as err:
+            captured_eviction_exceptions.append(
+                CapturedEvictionException(
+                    is_replaying=workflow.unsafe.is_replaying(), exception=err
+                )
+            )
+
+
+async def test_workflow_eviction_exception(client: Client):
+    assert not captured_eviction_exceptions
+
+    # Run workflow with no cache (forces eviction every step)
+    async with new_worker(
+        client, EvictionCaptureExceptionWorkflow, max_cached_workflows=0
+    ) as worker:
+        await client.execute_workflow(
+            EvictionCaptureExceptionWorkflow.run,
+            id=f"workflow-{uuid.uuid4()}",
+            task_queue=worker.task_queue,
+        )
+
+    # Confirm expected eviction replaying state and exception type
+    assert len(captured_eviction_exceptions) == 1
+    assert captured_eviction_exceptions[0].is_replaying
+    assert (
+        type(captured_eviction_exceptions[0].exception).__name__
+        == "_WorkflowBeingEvictedError"
+    )
+
+
 @dataclass
 class DynamicWorkflowValue:
     some_string: str