flip.flower.metrics

Flower metrics utilities — mirrors flip.nvflare.metrics for the Flower framework.

In Flower, clients return metrics in their reply Message via MetricRecord. The server-side strategy receives these in aggregate_train / aggregate_evaluate and should call handle_client_metrics to forward them to the Central Hub.

Only the fl-server should import from this module — it forwards to the Central Hub using credentials that must never reach the fl-client containers.

Usage (server-side, in a FedAvg strategy subclass):

from flip.flower.metrics import handle_client_metrics, handle_client_exception

def aggregate_train(self, server_round, replies):

for msg in replies:
handle_client_metrics(msg, server_round, self.model_id, self.flip) handle_client_exception(msg, self.model_id, self.flip)

return super().aggregate_train(server_round, replies)

Functions

`handle_client_metrics`() → None)	Forward per-client metrics from a Flower reply Message to the Central Hub.
`handle_client_exception`() → None)	Forward a crashed-client reply to the Central Hub and mark the run ERROR.

Module Contents

flip.flower.metrics.handle_client_metrics(msg: flwr.common.message.Message, server_round: int, model_id: str, flip: flip.FLIP = FLIP()) → None[source]

Forward per-client metrics from a Flower reply Message to the Central Hub.

Extracts all numeric metrics from the client’s MetricRecord and sends each one to the Central Hub via flip.send_metrics. The metric label is converted to uppercase to match the FLIP convention (e.g. “train_loss” -> “TRAIN_LOSS”).

Per-epoch metric keys following the “<label>.round_<N>” pattern are split so each data point is recorded against its own round number, letting the Hub plot intra-round progress (e.g. “train_loss.round_5” -> label=”TRAIN_LOSS”, round=5).

Only the fl-server should call this function — fl-clients must not hold the credentials needed to reach the Central Hub.

Parameters:

msg – A Flower reply Message from a client. Expected to contain a “metrics” MetricRecord and optionally a “config” ConfigRecord with a “site” key identifying the client.
server_round – The current server round number, used as the default x-axis value for any metric that does not embed its own round.
model_id – The FLIP model ID. Validated by the underlying flip implementation when it reaches the Central Hub; the handler itself is tolerant so LOCAL_DEV runs with placeholder ids work.
flip – The FLIP instance used to reach the Central Hub.

flip.flower.metrics.handle_client_exception(msg: flwr.common.message.Message, model_id: str, flip: flip.FLIP = FLIP()) → None[source]

Forward a crashed-client reply to the Central Hub and mark the run ERROR.

When a Flower client raises, the reply Message arrives with has_error() set. This helper both forwards the error string (so the Hub can display it alongside the model run) and transitions the run status to ERROR — without the latter, a crashed client would leave the Hub showing a still-running run indefinitely.

Only the fl-server should call this function — fl-clients must not hold the credentials needed to reach the Central Hub.

Parameters:

msg – A Flower reply Message from a client.
model_id – The FLIP model ID. Validated by the underlying flip implementation when it reaches the Central Hub.
flip – The FLIP instance used to reach the Central Hub.