feat: Add async hook, plugin, and flag tracker#463
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| self.__value: Any = None | ||
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| @classmethod | ||
| async def create(cls, key: str, context: Context, listener: Callable[[FlagValueChange], None], eval_fn: Callable, scheduler: AsyncCallbackScheduler) -> 'AsyncFlagValueChangeListener': |
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I'm not a fan of having 2 ways to create this (init and create) when the behavior would be different.
I can see why we are doing this though. Maybe we can just add some documentation to the init making it very clear you shouldn't use this method to instantiate the change listener?
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Overview
This slice adds the async counterparts of the SDK's hook and plugin extension points, plus the async flag tracker used by the async client:
AsyncHook(ldclient/hook.py) — abstract base for async hooks.before_evaluation/after_evaluationare coroutines awaited by the async client.AsyncPlugin(ldclient/plugin.py) — abstract base for async plugins.register()is a coroutine (allowing async initialization such as connecting to telemetry backends);get_hooks()remains synchronous and returnsAsyncHookinstances.AsyncFlagTrackerImpl/AsyncFlagValueChangeListener(ldclient/impl/async_flag_tracker.py) — the async flag tracker implementation.Unit tests are added in
ldclient/testing/test_async_hooks.pyandldclient/testing/test_async_flag_tracker.py.The async public classes carry the experimental
.. caution::block, matching the rest of the async surface.This PR depends only on already-merged foundation work and can be reviewed independently.
Tracked internally: SDK-2737
Note
Low Risk
Additive experimental async APIs and new implementation files; no changes to sync client evaluation or existing plugin contracts.
Overview
Adds experimental async extension points and flag-change tracking for
AsyncLDClient, paralleling the existing syncHook,Plugin, andFlagTrackerImpl.AsyncHookinhook.pymirrorsHookbut withasyncbefore_evaluation/after_evaluationcoroutines the async client will await.AsyncPlugininplugin.pyadds an asyncregister()forAsyncLDClientand synchronousget_hooks()returningAsyncHookinstances only (withAsyncHookimported alongsideHook).AsyncFlagTrackerImplandAsyncFlagValueChangeListenerimplement async flag-value change listeners: baseline evaluation on subscribe (no initial callback), re-evaluation on matchingFlagChangeevents, deduplication when the value is unchanged, and scheduling viaAsyncCallbackSchedulerso notifications work from worker threads without a running loop.Unit tests cover hook dispatch order (before forward, after reverse), per-hook isolated hook data, and tracker add/remove/thread-notify behavior.
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