Inject WorkloadState into instantiated client

doc/source/ref-changelog.md

@@ -22,6 +22,8 @@
 
   Using the `client_fn`, Flower clients can interchangeably run as standalone processes (i.e. via `start_client`) or in simulation (i.e. via `start_simulation`) without requiring changes to how the client class is defined and instantiated. Calling `start_numpy_client` is now deprecated.
 
+- **Introduced `WorkloadState`** ([#2564](https://github.com/adap/flower/pull/2564), [#2632](https://github.com/adap/flower/pull/2632))
+
 - **Update Flower Baselines**
 
   - FedProx ([#2210](https://github.com/adap/flower/pull/2210), [#2286](https://github.com/adap/flower/pull/2286), [#2509](https://github.com/adap/flower/pull/2509))

src/py/flwr/client/client.py

@@ -19,6 +19,7 @@
 
 from abc import ABC
 
+from flwr.client.workload_state import WorkloadState
 from flwr.common import (
     Code,
     EvaluateIns,
@@ -37,6 +38,8 @@
 class Client(ABC):
     """Abstract base class for Flower clients."""
 
+    state: WorkloadState
+
     def get_properties(self, ins: GetPropertiesIns) -> GetPropertiesRes:
         """Return set of client's properties.
 
@@ -138,6 +141,14 @@ def evaluate(self, ins: EvaluateIns) -> EvaluateRes:
             metrics={},
         )
 
+    def get_state(self) -> WorkloadState:
+        """Get the workload state from this client."""
+        return self.state
+
+    def set_state(self, state: WorkloadState) -> None:
+        """Apply a workload state to this client."""
+        self.state = state
+
     def to_client(self) -> Client:
         """Return client (itself)."""
         return self

src/py/flwr/client/flower.py

@@ -79,13 +79,14 @@ def __init__(
     def __call__(self, fwd: Fwd) -> Bwd:
         """."""
         # Execute the task
-        task_res = handle(
+        task_res, state_updated = handle(
             client_fn=self.client_fn,
+            state=fwd.state,
             task_ins=fwd.task_ins,
         )
         return Bwd(
             task_res=task_res,
-            state=WorkloadState(state={}),
+            state=state_updated,
         )
 
 

src/py/flwr/client/message_handler/message_handler.py

@@ -30,6 +30,7 @@
 )
 from flwr.client.secure_aggregation import SecureAggregationHandler
 from flwr.client.typing import ClientFn
+from flwr.client.workload_state import WorkloadState
 from flwr.common import serde
 from flwr.proto.task_pb2 import SecureAggregation, Task, TaskIns, TaskRes
 from flwr.proto.transport_pb2 import ClientMessage, Reason, ServerMessage
@@ -77,13 +78,17 @@ def handle_control_message(task_ins: TaskIns) -> Tuple[Optional[TaskRes], int]:
     return None, 0
 
 
-def handle(client_fn: ClientFn, task_ins: TaskIns) -> TaskRes:
+def handle(
+    client_fn: ClientFn, state: WorkloadState, task_ins: TaskIns
+) -> Tuple[TaskRes, WorkloadState]:
     """Handle incoming TaskIns from the server.
 
     Parameters
     ----------
     client_fn : ClientFn
         A callable that instantiates a Client.
+    state : WorkloadState
+        A dataclass storing the state for the workload being executed by the client.
     task_ins: TaskIns
         The task instruction coming from the server, to be processed by the client.
 
@@ -96,6 +101,7 @@ def handle(client_fn: ClientFn, task_ins: TaskIns) -> TaskRes:
     if server_msg is None:
         # Instantiate the client
         client = client_fn("-1")
+        client.set_state(state)
         # Secure Aggregation
         if task_ins.task.HasField("sa") and isinstance(
             client, SecureAggregationHandler
@@ -112,22 +118,24 @@ def handle(client_fn: ClientFn, task_ins: TaskIns) -> TaskRes:
                     sa=SecureAggregation(named_values=serde.named_values_to_proto(res)),
                 ),
             )
-            return task_res
+            return task_res, client.get_state()
         raise NotImplementedError()
-    client_msg = handle_legacy_message(client_fn, server_msg)
+    client_msg, updated_state = handle_legacy_message(client_fn, state, server_msg)
     task_res = wrap_client_message_in_task_res(client_msg)
-    return task_res
+    return task_res, updated_state
 
 
 def handle_legacy_message(
-    client_fn: ClientFn, server_msg: ServerMessage
-) -> ClientMessage:
+    client_fn: ClientFn, state: WorkloadState, server_msg: ServerMessage
+) -> Tuple[ClientMessage, WorkloadState]:
     """Handle incoming messages from the server.
 
     Parameters
     ----------
     client_fn : ClientFn
         A callable that instantiates a Client.
+    state : WorkloadState
+        A dataclass storing the state for the workload being executed by the client.
     server_msg: ServerMessage
         The message coming from the server, to be processed by the client.
 
@@ -144,15 +152,19 @@ def handle_legacy_message(
 
     # Instantiate the client
     client = client_fn("-1")
+    client.set_state(state)
     # Execute task
+    message = None
     if field == "get_properties_ins":
-        return _get_properties(client, server_msg.get_properties_ins)
+        message = _get_properties(client, server_msg.get_properties_ins)
     if field == "get_parameters_ins":
-        return _get_parameters(client, server_msg.get_parameters_ins)
+        message = _get_parameters(client, server_msg.get_parameters_ins)
     if field == "fit_ins":
-        return _fit(client, server_msg.fit_ins)
+        message = _fit(client, server_msg.fit_ins)
     if field == "evaluate_ins":
-        return _evaluate(client, server_msg.evaluate_ins)
+        message = _evaluate(client, server_msg.evaluate_ins)
+    if message:
+        return message, client.get_state()
     raise UnknownServerMessage()
 
 

src/py/flwr/client/message_handler/message_handler_test.py

@@ -19,6 +19,7 @@
 
 from flwr.client import Client
 from flwr.client.typing import ClientFn
+from flwr.client.workload_state import WorkloadState
 from flwr.common import (
     EvaluateIns,
     EvaluateRes,
@@ -133,7 +134,11 @@ def test_client_without_get_properties() -> None:
     disconnect_task_res, actual_sleep_duration = handle_control_message(
         task_ins=task_ins
     )
-    task_res = handle(client_fn=_get_client_fn(client), task_ins=task_ins)
+    task_res, state_updated = handle(  # pylint: disable=unused-variable
+        client_fn=_get_client_fn(client),
+        state=WorkloadState(state={}),
+        task_ins=task_ins,
+    )
 
     if not task_res.HasField("task"):
         raise ValueError("Task value not found")
@@ -197,7 +202,11 @@ def test_client_with_get_properties() -> None:
     disconnect_task_res, actual_sleep_duration = handle_control_message(
         task_ins=task_ins
     )
-    task_res = handle(client_fn=_get_client_fn(client), task_ins=task_ins)
+    task_res, updated_state = handle(  # pylint: disable=unused-variable
+        client_fn=_get_client_fn(client),
+        state=WorkloadState(state={}),
+        task_ins=task_ins,
+    )
 
     if not task_res.HasField("task"):
         raise ValueError("Task value not found")