feat: Add AsyncLDClient with FDv1 data system and public API - #480
feat: Add AsyncLDClient with FDv1 data system and public API#480jsonbailey wants to merge 4 commits into
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Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.
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| hooks = [] # type: List[AsyncHook] | ||
| with self.__hooks_lock.read(): | ||
| if len(self.__hooks) == 0: | ||
| return await block() |
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Hooks lock held across await
High Severity
When no hooks are registered, __evaluate_with_hooks awaits evaluation while still holding a threading ReadWriteLock read lock. A concurrent add_hook then blocks the event-loop thread on the write lock, so the reader never resumes and the process deadlocks. This is the common default path with an empty hook list.
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| 'variation': detail.variation_index, | ||
| 'reason': detail.reason, | ||
| 'version': flag['version'], | ||
| 'prerequisites': result.prerequisites, |
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Unbound result after flag error
Medium Severity
In all_flags_state, if evaluating a single flag raises, the except path sets detail but still reads result.prerequisites afterward. That raises UnboundLocalError and aborts the whole bootstrap payload instead of continuing with the other flags.
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Address review findings in the async client evaluation and shutdown paths: - __evaluate_with_hooks held the hooks read lock across `await block()` on the empty-hooks fast path. A concurrent sync add_hook() takes the write lock with a blocking wait, freezing the event-loop thread. Snapshot the hooks under the lock and release it before awaiting, mirroring the sync client's no-await safety. - all_flags_state referenced `result.prerequisites` unconditionally even when a per-flag evaluation raised, causing UnboundLocalError on the first failure or reuse of a neighbor's prerequisites on a later one. Bind the prerequisites safely in both branches so an error degrades only that flag. - __try_execute_stage swallowed asyncio.CancelledError via `except BaseException`, defeating cancellation and shutdown. Re-raise it. - _close_components stopped components in sequence with no isolation, so one failing stop() skipped the rest. Stop each component in its own try/except.
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Summary
Adds the async LaunchDarkly client (
AsyncLDClient) built onasyncio/aiohttp, wired to the FDv1 data system, plus the public API surface for constructing it. This is the first extraction slice from the async SDK implementation branch (epic SDK-60).What's included
ldclient/async_client.py—AsyncLDClientwith the FDv1 data system path.ldclient/impl/datasystem/async_fdv1.py— async FDv1 data system.ldclient/impl/datasystem/__init__.py— adds theAsyncDataSystemprotocol.ldclient/__init__.py,ldclient/client.py,ldclient/impl/client_common.py,ldclient/impl/stubs.py— public API / shared plumbing needed by the async client.ldclient/testing/mock_async_components.py,ldclient/testing/stub_util.py— async test doubles.ldclient/testing/test_async_client.py,ldclient/testing/test_sync_async_parity.py— coverage for the async client and sync/async API parity.Held back for a later PR (FDv2)
This slice is FDv1-only. The FDv2 data-system branch in
_make_data_system()(lazy imports ofasync_fdv2/datasourcev2.async_polling/async_streaming) is not included — those modules land in PR 11. For now the FDv2 path raisesNotImplementedError("FDv2 is not yet supported in the async client"). The_wire_data_source_sessionshelper (FDv2-only) was likewise omitted.Follow-ups
Verification
uv run pytest ldclient/testing/test_async_client.py ldclient/testing/test_sync_async_parity.py -q→ 21 passedpycodestyle,isort --check --atomic, andmypyclean on all changed filesasync_fdv2ordatasourcev2.async_*in the treeNote
Medium Risk
Large new experimental client surface touching flag evaluation, networking, and lifecycle; FDv2 is blocked but misconfiguration could surprise adopters until follow-up PRs land.
Overview
Introduces an experimental asyncio-based
AsyncLDClientwith explicitawait start()/close()(or async context manager), mirroring the sync client’s evaluation, events, hooks, and status APIs onAsyncConfigand aiohttp.Wires the client to a new
AsyncFDv1implementation and anAsyncDataSystemprotocol (streaming/polling via existing async datasource types). FDv2 is intentionally unsupported for now (NotImplementedErrorwhendatasystem_configis set).Public plumbing:
ldclientexposesAsyncLDClientvia lazy__getattr__;get_plugin_hooksnow takes a plugin sequence (syncLDClientupdated accordingly). AddsAsyncNullEventProcessor/AsyncNullUpdateProcessorfor offline and no-op paths.Tests:
test_async_client.py(lifecycle, variation, hooks, events) andtest_sync_async_parity.pyto guard sync/async API surface drift.Reviewed by Cursor Bugbot for commit 3cef7b5. Bugbot is set up for automated code reviews on this repo. Configure here.