"""Shared clients for kubernetes
avoids creating multiple kubernetes client objects,
each of which spawns an unused max-size thread pool
"""
from unittest.mock import Mock
import weakref
import kubernetes.client
from kubernetes.client import api_client
# FIXME: remove when instantiating a kubernetes client
# doesn't create N-CPUs threads unconditionally.
# monkeypatch threadpool in kubernetes api_client
# to avoid instantiating ThreadPools.
# This is known to work for kubernetes-4.0
# and may need updating with later kubernetes clients
_dummy_pool = Mock()
api_client.ThreadPool = lambda *args, **kwargs: _dummy_pool
_client_cache = {}
def shared_client(ClientType, *args, **kwargs):
"""Return a single shared kubernetes client instance
A weak reference to the instance is cached,
so that concurrent calls to shared_client
will all return the same instance until
all references to the client are cleared.
"""
kwarg_key = tuple((key, kwargs[key]) for key in sorted(kwargs))
cache_key = (ClientType, args, kwarg_key)
client = None
if cache_key in _client_cache:
# resolve cached weakref
# client can still be None after this!
client = _client_cache[cache_key]()
if client is None:
Client = getattr(kubernetes.client, ClientType)
client = Client(*args, **kwargs)
# cache weakref so that clients can be garbage collected
_client_cache[cache_key] = weakref.ref(client)
return client
