Using internal ip + port in a load balancer instead of URL exposed (#16119)

Co-authored-by: thomas chaton <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

src/lightning_app/CHANGELOG.md

@@ -13,7 +13,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
--
+
+- The LoadBalancer now uses internal ip + port instead of URL exposed ([#16119](https://github.com/Lightning-AI/lightning/pull/16119))
 
 
 ### Deprecated

src/lightning_app/components/serve/auto_scaler.py

@@ -429,7 +429,9 @@ def update_servers(self, server_works: List[LightningWork]):
         AutoScaler uses this method to increase/decrease the number of works.
         """
         old_servers = set(self._servers)
-        server_urls: List[str] = [server.url for server in server_works if server.url]
+        server_urls: List[str] = [
+            f"http://{server._internal_ip}:{server.port}" for server in server_works if server._internal_ip
+        ]
         new_servers = set(server_urls)
 
         if new_servers == old_servers:
@@ -458,12 +460,22 @@ def send_request_to_update_servers(self, servers: List[str]):
                 detail="Invalid authentication credentials",
                 headers={"WWW-Authenticate": "Basic"},
             ) from e
+
+        if not self._internal_ip:
+            return
+
         headers = {
             "accept": "application/json",
             "username": USERNAME,
             "Authorization": AUTHORIZATION_TYPE + " " + data,
         }
-        response = requests.put(f"{self.url}/system/update-servers", json=servers, headers=headers, timeout=10)
+
+        response = requests.put(
+            f"http://{self._internal_ip}:{self.port}/system/update-servers",
+            json=servers,
+            headers=headers,
+            timeout=10,
+        )
         response.raise_for_status()
 
     @staticmethod
@@ -735,7 +747,11 @@ def scale(self, replicas: int, metrics: dict) -> int:
     @property
     def num_pending_requests(self) -> int:
         """Fetches the number of pending requests via load balancer."""
-        return int(requests.get(f"{self.load_balancer.url}/num-requests").json())
+        if not self.load_balancer._internal_ip:
+            return 0
+        return int(
+            requests.get(f"http://{self.load_balancer._internal_ip}:{self.load_balancer.port}/num-requests").json()
+        )
 
     @property
     def num_pending_works(self) -> int: