nvflare.app_opt.sklearn.recipes.kmeans module

class KMeansFedAvgRecipe(*, name: str = 'kmeans_fedavg', min_clients: int, num_rounds: int = 5, n_clusters: int = 3, model_path: str | None = None, train_script: str, train_args: str = '', launch_external_process: bool = False, command: str = 'python3 -u', per_site_config: dict[str, dict] | None = None, key_metric: str = 'metrics')[source]

Bases: FedAvgRecipe

A recipe for Federated K-Means Clustering with Scikit-learn.

Recipe parameters, including train_args and nested per_site_config values, must never contain actual secrets. Read secrets from site environment variables or mounted files; references are supported only where documented in nvflare.recipe.secrets.

This recipe implements federated K-Means clustering using a mini-batch aggregation strategy. The aggregation follows the scheme defined in MiniBatchKMeans where each client’s results are treated as a mini-batch for updating global centers.

The recipe configures: - A federated job with initial n_clusters parameter - FedAvg controller for coordinating training rounds - Custom KMeansAssembler for mini-batch center aggregation - CollectAndAssembleModelAggregator for combining client updates - Script runners for client-side training execution

Training Process: - Round 0: Each client generates initial centers using k-means++. The server

collects all initial centers and performs one round of k-means to generate the initial global centers.

  • Subsequent rounds: Each client trains a local MiniBatchKMeans model starting from global centers. The server aggregates center and count information to update global centers using the mini-batch update rule.

Parameters:

  • name – Name of the federated learning job. Defaults to “kmeans_fedavg”.

  • min_clients – Minimum number of clients required to start a training round.

  • num_rounds – Number of federated training rounds to execute. Defaults to 5.

  • n_clusters – Number of clusters for K-Means. Defaults to 3.

  • model_path – Absolute path to a saved model file (.joblib). If provided, the file must exist at runtime. Used to load previously saved cluster centers.

  • train_script – Path to the training script that will be executed on each client.

  • train_args – Command line arguments to pass to the training script.

  • launch_external_process – Whether to launch the script in external process. Defaults to False.

  • command – If launch_external_process=True, command to run script (prepended to script). Defaults to “python3 -u”.

  • per_site_config – Deprecated constructor form of per-site configuration. New code should call set_per_site_config(recipe, config) immediately after construction. Nested values become part of the generated job definition and must not contain secrets.

  • key_metric – Metric used to determine if the model is globally best. If validation metrics are a dict, key_metric selects the metric used for global model selection. Higher values must indicate a better model. Defaults to “metrics” (which corresponds to the homogeneity score sent by the K-Means client).

Example

Basic usage with same config for all clients:

```python recipe = KMeansFedAvgRecipe(

name=”kmeans_iris”, min_clients=3, num_rounds=5, n_clusters=3, train_script=”src/kmeans_fl.py”, train_args=”–data_path /tmp/data/iris.csv”,

)

from nvflare.recipe import SimEnv env = SimEnv(num_clients=3) run = recipe.execute(env) print(“Result:”, run.get_result()) ```

Per-site configuration:

```python from nvflare.app_opt.sklearn import KMeansFedAvgRecipe from nvflare.recipe import set_per_site_config

recipe = KMeansFedAvgRecipe(

name=”kmeans_iris”, min_clients=3, num_rounds=5, n_clusters=3, train_script=”src/kmeans_fl.py”,

) set_per_site_config(

recipe, {

“site-1”: {“train_args”: “–data_path /tmp/data/site1.csv –train_start 0 –train_end 50”}, “site-2”: {“train_args”: “–data_path /tmp/data/site2.csv –train_start 50 –train_end 100”}, “site-3”: {“train_args”: “–data_path /tmp/data/site3.csv –train_start 100 –train_end 150”},

},

)

Note

This recipe uses a custom KMeansAssembler that implements the mini-batch K-Means aggregation logic. The assembler maintains historical center and count information across rounds for proper weighted averaging.

This is base class of a recipe. Recipes are implemented by jobs. A concrete recipe must provide the job for recipe implementation.

Security contract – no secrets in recipe parameters:

Recipe parameters (train_args, task_args, eval_args, per_site_config, config overrides, dicts passed to add_client_config/add_server_config, exec params, etc.) can be written in clear text into generated job configuration. These parameters and their nested values must never contain actual passwords, API keys, tokens, private keys, or other credentials. Instead, read secrets from site environment variables or mounted secret files inside your code, or pass a placeholder created with nvflare.recipe.secrets.secret_ref() or nvflare.recipe.secrets.secret_file_ref() at a supported runtime boundary. See nvflare.recipe.secrets for the supported parameter locations.

Before export or run, recipes scan their parameters with heuristics and emit nvflare.recipe.secrets.PotentialSecretWarning when a value looks like an actual secret. The scan is best-effort: absence of a warning does not prove a parameter is safe to share.

param job:

the job that implements the recipe.