Add thread-safe handler initialization using double-checked locking

[ImMin5]

Category

• New feature
• Bug fix
• Improvement
• Refactor
• etc

Description

• Add thread-safe handler initialization using double-checked locking

Known issue

When the server starts and both the first and second requests arrive simultaneously, the handler was being initialized twice.

To resolve this, a thread lock was introduced. Only the first and second requests are affected by the lock, and since subsequent requests bypass the initialization logic, there appears to be no performance issue.

[Copilot]

Pull Request Overview

Implements a thread-safe double-checked locking pattern for handler initialization to prevent duplicate setups under concurrent requests.

• Introduce a module-level lock and wrap _check_init_state in a double-checked lock.
• Ensure only one initialization of handlers on simultaneous startup requests.

Comments suppressed due to low confidence (3)

src/spaceone/core/handler/init.py:29

• [nitpick] The lock name _HANDLER_THREAD_LOCK is generic; consider renaming it to _HANDLER_INIT_LOCK to clarify that it's specifically for handler initialization.

_HANDLER_THREAD_LOCK = threading.Lock()

src/spaceone/core/handler/init.py:148

• [nitpick] Add a brief docstring for _check_init_state explaining the double-checked locking logic to help future maintainers understand the thread-safety mechanism.

def _check_init_state() -> None:

src/spaceone/core/handler/init.py:149

• Consider adding a concurrent unit test that calls _check_init_state from multiple threads to verify _init_handlers is invoked only once under simultaneous access.

if not _HANDLER_INFO["init"]: