[Serve] Update min_replicas (#3057)

* fix

* add a smoke test

* change comment

* revert task.yaml

sky/serve/autoscalers.py

@@ -80,9 +80,9 @@ def update_version(self, version: int,
                          f'latest version: {self.latest_version}')
             return
         self.latest_version = version
-        self.min_nodes = spec.min_replicas
-        self.max_nodes = (spec.max_replicas if spec.max_replicas is not None
-                          else spec.min_replicas)
+        self.min_replicas = spec.min_replicas
+        self.max_replicas = (spec.max_replicas if spec.max_replicas is not None
+                             else spec.min_replicas)
         # Reclip self.target_num_replicas with new min and max replicas.
         self.target_num_replicas = max(
             self.min_replicas, min(self.max_replicas, self.target_num_replicas))

tests/skyserve/update/num_min_one.yaml

@@ -0,0 +1,15 @@
+service:
+  readiness_probe:
+    path: /health
+    initial_delay_seconds: 20
+  replica_policy:
+    min_replicas: 1
+
+resources:
+  ports: 8080
+  cloud: gcp
+  cpus: 2+
+
+workdir: examples/serve/http_server
+
+run: python3 server.py --port 8080

tests/skyserve/update/num_min_two.yaml

@@ -0,0 +1,16 @@
+service:
+  readiness_probe:
+    path: /health
+    initial_delay_seconds: 20
+  replica_policy:
+    min_replicas: 2
+
+resources:
+  ports: 8080
+  cloud: gcp
+  cpus: 2+
+
+workdir: examples/serve/http_server
+
+run: python3 server.py --port 8080
+

tests/test_smoke.py

@@ -3088,6 +3088,30 @@ def test_skyserve_update():
     run_one_test(test)
 
 
+@pytest.mark.gcp
+@pytest.mark.sky_serve
+def test_skyserve_update_autoscale():
+    """Test skyserve update with autoscale"""
+    name = _get_service_name()
+    test = Test(
+        f'test-skyserve-update-autoscale',
+        [
+            f'sky serve up -n {name} -y tests/skyserve/update/num_min_two.yaml',
+            _SERVE_WAIT_UNTIL_READY.format(name=name, replica_num=2),
+            f'{_get_serve_endpoint(name)}; curl -L http://$endpoint | grep "Hi, SkyPilot here"',
+            f'sky serve update {name} -y tests/skyserve/update/num_min_one.yaml',
+            # sleep before update is registered.
+            'sleep 20',
+            # Timeout will be triggered when update fails.
+            _SERVE_WAIT_UNTIL_READY.format(name=name, replica_num=1),
+            f'{_get_serve_endpoint(name)}; curl -L http://$endpoint | grep "Hi, SkyPilot here!"',
+        ],
+        _TEARDOWN_SERVICE.format(name=name),
+        timeout=20 * 60,
+    )
+    run_one_test(test)
+
+
 # ------- Testing user ray cluster --------
 def test_user_ray_cluster(generic_cloud: str):
     name = _get_cluster_name()