[serve] Call serve.init() before initializing backends (#7922)

python/ray/serve/tests/test_handle.py

@@ -0,0 +1,29 @@
+import ray
+from ray import serve
+
+import requests
+
+
+def test_handle_in_endpoint(serve_instance):
+    serve.init()
+
+    class Endpoint1:
+        def __call__(self, flask_request):
+            return "hello"
+
+    class Endpoint2:
+        def __init__(self):
+            self.handle = serve.get_handle("endpoint1", missing_ok=True)
+
+        def __call__(self):
+            return ray.get(self.handle.remote())
+
+    serve.create_endpoint("endpoint1", "/endpoint1", methods=["GET", "POST"])
+    serve.create_backend(Endpoint1, "endpoint1:v0")
+    serve.link("endpoint1", "endpoint1:v0")
+
+    serve.create_endpoint("endpoint2", "/endpoint2", methods=["GET", "POST"])
+    serve.create_backend(Endpoint2, "endpoint2:v0")
+    serve.link("endpoint2", "endpoint2:v0")
+
+    assert requests.get("http://127.0.0.1:8000/endpoint2").text == "hello"