Expose gRPC parameters in start_client() and start_numpy_client()

src/py/flwr/client/app.py

@@ -34,6 +34,7 @@ def start_client(
     client: Client,
     grpc_max_message_length: int = GRPC_MAX_MESSAGE_LENGTH,
     root_certificates: Optional[bytes] = None,
+    wait_for_ready: bool = False,
 ) -> None:
     """Start a Flower Client which connects to a gRPC server.
 
@@ -55,6 +56,8 @@ class `flwr.client.Client`.
             The PEM-encoded root certificates as a byte string. If provided, a secure
             connection using the certificates will be established to a
             SSL-enabled Flower server.
+        wait_for_ready: bool (default: False). If set to True, the client does not
+            fail fast, but waits until a connection to the server can be established.
 
     Returns
     -------
@@ -84,6 +87,7 @@ class `flwr.client.Client`.
             server_address,
             max_message_length=grpc_max_message_length,
             root_certificates=root_certificates,
+            wait_for_ready=wait_for_ready,
         ) as conn:
             receive, send = conn
 
@@ -112,6 +116,7 @@ def start_numpy_client(
     client: NumPyClient,
     grpc_max_message_length: int = GRPC_MAX_MESSAGE_LENGTH,
     root_certificates: Optional[bytes] = None,
+    wait_for_ready: bool = False,
 ) -> None:
     """Start a Flower NumPyClient which connects to a gRPC server.
 
@@ -133,6 +138,8 @@ class `flwr.client.NumPyClient`.
             The PEM-encoded root certificates a byte string. If provided, a secure
             connection using the certificates will be established to a
             SSL-enabled Flower server.
+        wait_for_ready: bool (default: False). If set to True, the client does not
+            fail fast, but waits until a connection to the server can be established.
 
     Returns
     -------
@@ -173,4 +180,5 @@ class `flwr.client.NumPyClient`.
         client=flower_client,
         grpc_max_message_length=grpc_max_message_length,
         root_certificates=root_certificates,
+        wait_for_ready=wait_for_ready,
     )

src/py/flwr/client/grpc_client/connection.py

@@ -44,6 +44,7 @@ def grpc_connection(
     server_address: str,
     max_message_length: int = GRPC_MAX_MESSAGE_LENGTH,
     root_certificates: Optional[bytes] = None,
+    wait_for_ready: bool = False,
 ) -> Iterator[Tuple[Callable[[], ServerMessage], Callable[[ClientMessage], None]]]:
     """Establish an insecure gRPC connection to a gRPC server.
 
@@ -64,6 +65,8 @@ def grpc_connection(
         The PEM-encoded root certificates as a byte string. If provided, a secure
         connection using the certificates will be established to a SSL-enabled
         Flower server.
+    wait_for_ready: bool (default: False). If set to True, the client does not
+        fail fast, but waits until a connection to the server can be established.
 
     Returns
     -------
@@ -108,7 +111,9 @@ def grpc_connection(
     )
     stub = FlowerServiceStub(channel)
 
-    server_message_iterator: Iterator[ServerMessage] = stub.Join(iter(queue.get, None))
+    server_message_iterator: Iterator[ServerMessage] = stub.Join(
+        iter(queue.get, None), wait_for_ready=wait_for_ready
+    )
 
     receive: Callable[[], ServerMessage] = lambda: next(server_message_iterator)
     send: Callable[[ClientMessage], None] = lambda msg: queue.put(msg, block=False)