federer/dist/src/server/utils/ClientPool.d.ts

Experiments in asynchronous federated learning and decentralized learning

/**
 * Helper class to keep track of the state of clients. Clients can be marked as
 * either "available" (meaning that they are not currently training, and are
 * eligible to start training), or "training" (meaning that they have been given
 * a training task, and we are awaiting results).
 *
 * Clients are tracked by their socket ID, which is a `string`.
 *
 * The methods in this class use assertions to enforce the following invariants:
 *
 * - All clients start in the available state
 * - A client is either training or available, but never both
 * - A client can only transition from available to training, or from training
 *   to available; it cannot transition to the state that it is currently in
 *
 * These invariants are helpful to debug server implementations, and to ensure
 * the reported numbers are accurate.
 */
export declare class ClientPool {
    #private;
    /**
     * Adds a client to the pool, in the "available" state.
     *
     * @throws if the client is already in the pool.
     */
    addAvailableClient(client: string): void;
    /** Returns whether the client is in the "available" state */
    isAvailable(client: string): boolean;
    /** Returns whether the client is in the "training" state. */
    isTraining(client: string): boolean;
    /**
     * Changes the state of a client.
     *
     * @throws if the client is already in the target state
     */
    transition(client: string, newState: "training" | "available"): void;
    /**
     * Removes a client from the pool.
     *
     * @returns `true` if it was removed, `false` if it wasn't in the pool.
     */
    delete(client: string): boolean;
    /** Returns whether a client is in the pool. */
    has(client: string): boolean;
    /** Number of clients in the pool in total. */
    get size(): number;
    /** Number of clients in the "training" state. */
    get numberTraining(): number;
    /** Number of clients in the "available" state. */
    get numberAvailable(): number;
    get clients(): ReadonlySet<string>;
    get available(): ReadonlySet<string>;
    get training(): ReadonlySet<string>;
    get percentTraining(): number;
    /**
     * Samples `n` clients without replacement from the list of available clients,
     * using reservoir sampling.
     *
     * @returns array of `n` sampled client IDs
     * @throws if there are not enough available clients
     */
    sampleAvailable(n: number): string[];
}
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