[App] Fix `AutoScaler` trying to replicate multiple works in a single machine (#15991)

* dont try to replicate new works in the existing machine

* update chglog

* Update comment

* Update src/lightning_app/components/auto_scaler.py

* add test

src/lightning_app/CHANGELOG.md

@@ -43,6 +43,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed Registration for CloudComputes of Works in `L.app.structures` ([#15964](https://github.com/Lightning-AI/lightning/pull/15964))
 
 
+- Fixed `AutoScaler` raising an exception when non-default cloud compute is specified ([#15991](https://github.com/Lightning-AI/lightning/pull/15991))
+
+
 ## [1.8.4] - 2022-12-08
 
 ### Added

src/lightning_app/components/auto_scaler.py

@@ -449,8 +449,15 @@ class AutoScaler(LightningFlow):
 
     def create_work(self) -> LightningWork:
         """Replicates a LightningWork instance with args and kwargs provided via ``__init__``."""
+        cloud_compute = self._work_kwargs.get("cloud_compute", None)
+        self._work_kwargs.update(
+            dict(
                 # TODO: Remove `start_with_flow=False` for faster initialization on the cloud
-        self._work_kwargs.update(dict(start_with_flow=False))
+                start_with_flow=False,
+                # don't try to create multiple works in a single machine
+                cloud_compute=cloud_compute.clone() if cloud_compute else None,
+            )
+        )
         return self._work_cls(*self._work_args, **self._work_kwargs)
 
     def add_work(self, work) -> str:

tests/tests_app/components/test_auto_scaler.py

@@ -3,7 +3,7 @@ from unittest.mock import patch
 
 import pytest
 
-from lightning_app import LightningWork
+from lightning_app import CloudCompute, LightningWork
 from lightning_app.components import AutoScaler
 
 
@@ -90,3 +90,11 @@ def test_scale(replicas, metrics, expected_replicas):
     )
 
     assert auto_scaler.scale(replicas, metrics) == expected_replicas
+
+
+def test_create_work_cloud_compute_cloned():
+    """Test CloudCompute is cloned to avoid creating multiple works in a single machine."""
+    cloud_compute = CloudCompute("gpu")
+    auto_scaler = AutoScaler(EmptyWork, cloud_compute=cloud_compute)
+    _ = auto_scaler.create_work()
+    assert auto_scaler._work_kwargs["cloud_compute"] is not cloud_compute