ansible_mitogen: Evolution of NewStylePlanner ALWAYS_FORK_MODULES

[moreati]

ansible_mitogen.planner.NewStylePlanner.ALWAYS_FORK_MODULES is a frozenset of Ansible module names (full qualified and unqualified) the Mitogen should treat as single-shot. The in-memory imported Python module cannot be reused, thus Mitogen must reinstantiate it each time.

mitogen/ansible_mitogen/planner.py

Lines 337 to 347 in 3656979

	#: Module names appearing in this set always require forking, usually due
	#: to some terminal leakage that cannot be worked around in any sane
	#: manner.
	ALWAYS_FORK_MODULES = frozenset([
	'dnf', # issue #280; py-dnf/hawkey need therapy
	'firewalld', # issue #570: ansible module_utils caches dbus conn
	'ansible.legacy.dnf', # issue #776
	'ansible.builtin.dnf', # issue #832
	'freeipa.ansible_freeipa.ipaautomember', # issue #1216
	'freeipa.ansible_freeipa.ipaautomountkey',
	'freeipa.ansible_freeipa.ipaautomountlocation',

Problems

• Bad name: ALWAYS_FORK describes an implementation detail, not the intent/purpose
• Bad API: exposes an implementation detail
• Brittle: the list is long, incomplete, and static
• High maintenance: fixing a particular instance requires a PR and release cycle
• Obscure: it is very unobvious that aparticular Ansible failure has any connection with ALWAYS_FORK_MODULES

Ideas

• Seal implementation behind methods/properties
• Fully qualify names before checking them (e.g. dnf vs ansible.legacy.dnf vs ansible.builtin.dnf)
• Make configurable (e.g. environment variable, Ansible plugin property)
• Mechanism for Ansible modules to declare themself multi or single shot (e.g. class attribute mitogen_reuse = True|False|None)
• Provide extension mechanism(s)

refs #1216, #1255, #1327