# Copyright 2020 Flower Labs GmbH. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Flower ClientManager."""
import random
import threading
from abc import ABC, abstractmethod
from logging import INFO
from typing import Dict, List, Optional
from flwr.common.logger import log
from .client_proxy import ClientProxy
from .criterion import Criterion
[docs]class ClientManager(ABC):
"""Abstract base class for managing Flower clients."""
[docs] @abstractmethod
def num_available(self) -> int:
"""Return the number of available clients.
Returns
-------
num_available : int
The number of currently available clients.
"""
[docs] @abstractmethod
def register(self, client: ClientProxy) -> bool:
"""Register Flower ClientProxy instance.
Parameters
----------
client : flwr.server.client_proxy.ClientProxy
Returns
-------
success : bool
Indicating if registration was successful. False if ClientProxy is
already registered or can not be registered for any reason.
"""
[docs] @abstractmethod
def unregister(self, client: ClientProxy) -> None:
"""Unregister Flower ClientProxy instance.
This method is idempotent.
Parameters
----------
client : flwr.server.client_proxy.ClientProxy
"""
[docs] @abstractmethod
def all(self) -> Dict[str, ClientProxy]:
"""Return all available clients."""
[docs] @abstractmethod
def wait_for(self, num_clients: int, timeout: int) -> bool:
"""Wait until at least `num_clients` are available."""
[docs] @abstractmethod
def sample(
self,
num_clients: int,
min_num_clients: Optional[int] = None,
criterion: Optional[Criterion] = None,
) -> List[ClientProxy]:
"""Sample a number of Flower ClientProxy instances."""
[docs]class SimpleClientManager(ClientManager):
"""Provides a pool of available clients."""
def __init__(self) -> None:
self.clients: Dict[str, ClientProxy] = {}
self._cv = threading.Condition()
def __len__(self) -> int:
"""Return the number of available clients.
Returns
-------
num_available : int
The number of currently available clients.
"""
return len(self.clients)
[docs] def num_available(self) -> int:
"""Return the number of available clients.
Returns
-------
num_available : int
The number of currently available clients.
"""
return len(self)
[docs] def wait_for(self, num_clients: int, timeout: int = 86400) -> bool:
"""Wait until at least `num_clients` are available.
Blocks until the requested number of clients is available or until a
timeout is reached. Current timeout default: 1 day.
Parameters
----------
num_clients : int
The number of clients to wait for.
timeout : int
The time in seconds to wait for, defaults to 86400 (24h).
Returns
-------
success : bool
"""
with self._cv:
return self._cv.wait_for(
lambda: len(self.clients) >= num_clients, timeout=timeout
)
[docs] def register(self, client: ClientProxy) -> bool:
"""Register Flower ClientProxy instance.
Parameters
----------
client : flwr.server.client_proxy.ClientProxy
Returns
-------
success : bool
Indicating if registration was successful. False if ClientProxy is
already registered or can not be registered for any reason.
"""
if client.cid in self.clients:
return False
self.clients[client.cid] = client
with self._cv:
self._cv.notify_all()
return True
[docs] def unregister(self, client: ClientProxy) -> None:
"""Unregister Flower ClientProxy instance.
This method is idempotent.
Parameters
----------
client : flwr.server.client_proxy.ClientProxy
"""
if client.cid in self.clients:
del self.clients[client.cid]
with self._cv:
self._cv.notify_all()
[docs] def all(self) -> Dict[str, ClientProxy]:
"""Return all available clients."""
return self.clients
[docs] def sample(
self,
num_clients: int,
min_num_clients: Optional[int] = None,
criterion: Optional[Criterion] = None,
) -> List[ClientProxy]:
"""Sample a number of Flower ClientProxy instances."""
# Block until at least num_clients are connected.
if min_num_clients is None:
min_num_clients = num_clients
self.wait_for(min_num_clients)
# Sample clients which meet the criterion
available_cids = list(self.clients)
if criterion is not None:
available_cids = [
cid for cid in available_cids if criterion.select(self.clients[cid])
]
if num_clients > len(available_cids):
log(
INFO,
"Sampling failed: number of available clients"
" (%s) is less than number of requested clients (%s).",
len(available_cids),
num_clients,
)
return []
sampled_cids = random.sample(available_cids, num_clients)
return [self.clients[cid] for cid in sampled_cids]