feat(framework) Enable installation of FAB in ClientApp process

src/py/flwr/client/app.py

@@ -440,7 +440,10 @@ def _on_backoff(retry_state: RetryState) -> None:
  run: Run = runs[run_id]
  if get_fab is not None and run.fab_hash:
  fab = get_fab(run.fab_hash)
- install_from_fab(fab.content, flwr_path, True)
+ if isolation is None or isolation == ISOLATION_MODE_SUBPROCESS:
+ # If `ClientApp` runs in the same process, or a
+ # subprocess, install the FAB
+ install_from_fab(fab.content, flwr_path, True)
  fab_id, fab_version = get_fab_metadata(fab.content)
  else:
  fab = None

src/py/flwr/client/clientapp/app.py

@@ -21,6 +21,7 @@
 
 import grpc
 
+from flwr.cli.install import install_from_fab
 from flwr.client.client_app import ClientApp, LoadClientAppError
 from flwr.common import Context, Message
 from flwr.common.constant import ErrorCode
@@ -115,8 +116,13 @@ def run_clientapp( # pylint: disable=R0914
  token = get_token(stub)
  time.sleep(1)
 
- # Pull Message, Context, and Run from SuperNode
- message, context, run, _ = pull_message(stub=stub, token=token)
+ # Pull Message, Context, Run and (optional) FAB from SuperNode
+ message, context, run, fab = pull_message(stub=stub, token=token)
+
+ # Install FAB, if provided
+ if fab:
+ log(DEBUG, "Flower ClientApp starts FAB installation.")
+ install_from_fab(fab.content, flwr_dir=None, skip_prompt=True)
 
  load_client_app_fn = get_load_client_app_fn(
  default_app_ref="",