Use alternative endpoint on client side

Author: NickCao

packages/jumpstarter/jumpstarter/client/client.py

@@ -10,6 +10,7 @@
 
 from jumpstarter.client import DriverClient
 from jumpstarter.common.importlib import import_class
+from jumpstarter.common.grpc import aio_secure_channel
 
 
 @asynccontextmanager
@@ -26,6 +27,7 @@ async def client_from_channel(
     stack: ExitStack,
     allow: list[str],
     unsafe: bool,
+    use_alternative_endpoints: bool = True,
 ) -> DriverClient:
     topo = defaultdict(list)
     last_seen = {}
@@ -34,6 +36,25 @@ async def client_from_channel(
 
     response = await jumpstarter_pb2_grpc.ExporterServiceStub(channel).GetReport(empty_pb2.Empty())
 
+    if use_alternative_endpoints:
+        for endpoint in response.alternative_endpoints:
+            if endpoint.certificate:
+                attempted_channel = aio_secure_channel(
+                    endpoint.endpoint,
+                    grpc.ssl_channel_credentials(root_certificates=endpoint.certificate.encode()),
+                )  # TODO: set token
+                try:
+                    response = await jumpstarter_pb2_grpc.ExporterServiceStub(attempted_channel).GetReport(
+                        empty_pb2.Empty()
+                    )
+                except Exception:
+                    pass  # TODO: log failed attempt
+                else:
+                    channel = attempted_channel
+                    break
+            else:
+                continue
+
     for index, report in enumerate(response.reports):
         topo[index] = []