`certificate-authority-data` from kubeconfig fails for long-running process due to tmpfs cleanup

[PaulFurtado]

What happened (please include outputs or screenshots):
Long-running applications using a kubeconfig with certificate-authority-data encounter errors like:

Max retries exceeded with url: /api/v1/pods?fieldSelector=spec.nodeName%3Dip-172-18-66-203.ec2.internal (Caused by SSLError(FileNotFoundError(2, 'No such file or directory'),))

What you expected to happen:
Client should not expect tempfiles to live indefinitely. It is extremely common for servers to reap tempfiles.

Anything else we need to know?:
If you create a client you can easily see that it is using a temp file that cannot go away for the duration of the client:

>>> import kubernetes.config
>>> kubernetes.config.load_kube_config()
>>> api_client = kubernetes.client.ApiClient()
>>> api_client.rest_client.pool_manager.connection_pool_kw["ca_certs"]
'/tmp/tmpqkht2v2g'

You can reproduce the issue by deleting that temp file and attempting to make a request.

Code is here:

python/kubernetes/base/config/kube_config.py

Lines 63 to 78 in 1271465

	def _create_temp_file_with_content(content, temp_file_path=None):
	if len(_temp_files) == 0:
	atexit.register(_cleanup_temp_files)
	# Because we may change context several times, try to remember files we
	# created and reuse them at a small memory cost.
	content_key = str(content)
	if content_key in _temp_files:
	return _temp_files[content_key]
	if temp_file_path and not os.path.isdir(temp_file_path):
	os.makedirs(name=temp_file_path)
	fd, name = tempfile.mkstemp(dir=temp_file_path)
	os.close(fd)
	_temp_files[content_key] = name
	with open(name, 'wb') as fd:
	fd.write(content.encode() if isinstance(content, str) else content)
	return name

In order for this to work reliably for long-running processes on standard linux systems, the temp file really needs to be created for each request rather than a single time at startup.

That said, on linux systems, a potential hack would be to use /proc/self/fd/<fileno> instead of the temfile path since that would share the lifecycle of the process.

Environment:

• Python version (python --version): 3.6
• Python client version (pip list | grep kubernetes): 21.7.0

[roycaihw]

/assign @yliaog

[yliaog]

it seems reasonable, do you mind to send a PR?

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