[concurrency] client kickstart file generation may fail at startup

[anthonygego]

During the route initialization process, the client_pages module is loaded to add the route to the client kickstart files.

ICTV/ictv/flask/mapping.py

Line 7 in 97c8dcb

from ictv.client.pages import client_pages

However, this module also generates the kickstart zip when it is loaded the first time.

ICTV/ictv/client/pages/client_pages.py

Line 84 in 97c8dcb

make_system_zip()

In a multi-threaded/process environnement, the function generating the zip file is called multiple times in parallel, and may try to unlink a file that has already been unlinked by a parallel process. This ends up with a FileNotFoundError exception being raised at the application startup if such a case occurs.

ICTV/ictv/client/pages/client_pages.py

Lines 54 to 64 in 97c8dcb

	def make_system_zip():
	system_zip_path = os.path.join(get_root_path(), 'client', 'ks', 'system' + os.extsep + 'zip')
	if os.path.exists(system_zip_path):
	os.unlink(system_zip_path)
	def add_file(file):
	system_zip.write(os.path.join(get_root_path(), 'client', 'ks', file), arcname=file)
	with ZipFile(system_zip_path, 'w') as system_zip:
	add_file(os.path.join('etc', 'pam.d', 'xserver'))
	add_file(os.path.join('home', 'ictv', '.xinitrc'))

Writing the file in parallel should also be avoided in case ZipFile does not implement an internal lock/is not threadsafe.