fix(analytics): allow capability to offload reportExposure to async thread (SDK-80) by tylerjroach · Pull Request #181 · mixpanel/mixpanel-python

tylerjroach · 2026-06-30T17:07:31Z

Summary

Exposure tracking on the sync path called the user's tracker — and therefore an HTTP POST — inline, blocking every get_variant / get_variant_value / is_enabled call by the full /track round trip. The async paths already use asyncio.create_task; only the sync paths were paying the cost.

Add an optional exposure_executor: concurrent.futures.Executor | None = None field to FlagsConfig (inherited by both LocalFlagsConfig and RemoteFlagsConfig). When set, the sync providers dispatch the tracker call via executor.submit; flag evaluation returns as soon as the local logic finishes. None (the default) preserves the existing inline behavior — no breaking change for current users.

Usage

from concurrent.futures import ThreadPoolExecutor
from mixpanel.flags.types import LocalFlagsConfig

executor = ThreadPoolExecutor(max_workers=1, thread_name_prefix="mixpanel-exposure")
config = LocalFlagsConfig(exposure_executor=executor)

Context

Linear: SDK-80. Mirrors mixpanel-java#85. Audit-driven; same fix being applied to mixpanel-ruby and mixpanel-go in parallel PRs.

Test plan

Full flags suite passes (83 tests, including the existing inline-exposure tests — exposure_executor=None keeps the old behavior unchanged)
New test on both sync local and sync remote providers asserts the tracker runs on the executor's thread (thread_name_prefix="exposure") and not the calling thread

…hread Exposure tracking on the sync path called the user's tracker (and therefore an HTTP POST) inline, blocking every getVariant / getVariantValue / isEnabled call by the full /track round trip. The async paths already use asyncio.create_task; only the sync path was paying the cost. Add an optional `exposure_executor: concurrent.futures.Executor` field to FlagsConfig. When set, the sync providers dispatch the tracker call via executor.submit so flag evaluation returns as soon as the local logic finishes. None (the default) preserves the existing inline behavior. Mirrors mixpanel-java#85. Co-Authored-By: Claude Opus 4.7 <[email protected]>

codecov · 2026-06-30T17:11:32Z

Codecov Report

❌ Patch coverage is 97.38220% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.99%. Comparing base (58d9c38) to head (8e167f4).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
mixpanel/flags/utils.py	80.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #181      +/-   ##
==========================================
+ Coverage   94.50%   95.99%   +1.49%     
==========================================
  Files          12       13       +1     
  Lines        1947     3299    +1352     
  Branches      116      224     +108     
==========================================
+ Hits         1840     3167    +1327     
- Misses         70       88      +18     
- Partials       37       44       +7

Flag	Coverage Δ
openfeature-provider	`45.43% <30.55%> (-8.34%)`	⬇️

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…rage - Add an "Async Exposure Tracking" section to the openfeature-provider README showing how to configure a ThreadPoolExecutor. - Add tests covering the manual track_exposure_event API path (previously only the implicit-via-get_variant path was covered). - Add explicit tests asserting the default (None) still runs inline on the calling thread. Co-Authored-By: Claude Opus 4.7 <[email protected]>

linear-code · 2026-06-30T18:26:14Z

SDK-80

tylerjroach · 2026-07-02T15:25:09Z

@greptileai

greptile-apps · 2026-07-02T15:28:29Z

Confidence Score: 5/5

Safe to merge; the change is purely additive and the default None path is unchanged.

All existing behavior is preserved by default. The only noted gap is that _log_tracker_future_exception calls future.exception() without a future.cancelled() guard, which can raise CancelledError in the done-callback when an executor is shut down with cancel_futures=True. This is a narrow edge case with no data-loss consequence.

mixpanel/flags/utils.py — the _log_tracker_future_exception cancellation guard.

Important Files Changed

Filename	Overview
mixpanel/flags/utils.py	Adds `dispatch_exposure` helper with inline/executor dispatch and done-callback for error logging; missing cancellation guard in `_log_tracker_future_exception`.
mixpanel/flags/types.py	Adds `exposure_executor: Optional[Executor] = None` to `FlagsConfig`; `arbitrary_types_allowed=True` already present so Pydantic handles it correctly.
mixpanel/flags/local_feature_flags.py	Replaces inline tracker call with `_dispatch_exposure` delegation; clean, no logic changes to flag evaluation.
mixpanel/flags/remote_feature_flags.py	Same pattern as local provider — tracker calls replaced with `_dispatch_exposure`; `EXPOSURE_EVENT` import retained (used elsewhere in the file).
mixpanel/flags/test_utils.py	Adds unit tests for inline dispatch and executor error-logging; good coverage of the new helper.
mixpanel/flags/test_local_feature_flags.py	Adds three tests covering default inline behavior and executor off-thread dispatch for local provider.
mixpanel/flags/test_remote_feature_flags.py	Mirrors local provider tests for remote provider; symmetric and complete.
openfeature-provider/README.md	Adds documentation for the new async exposure tracking option with a usage example; accurate and clear.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["get_variant / is_enabled (sync)"] --> B["_dispatch_exposure()"]
    B --> C["dispatch_exposure(tracker, executor, ...)"]
    C --> D{executor is None?}
    D -- Yes --> E["tracker(...) inline\n(blocking, existing behavior)"]
    D -- No --> F["executor.submit(tracker, ...)"]
    F --> G["future.add_done_callback\n(_log_tracker_future_exception)"]
    G --> H{future exception?}
    H -- Yes --> I["logger.error(...)"]
    H -- No --> J["done"]
    F --> K["return immediately\n(non-blocking)"]

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    A["get_variant / is_enabled (sync)"] --> B["_dispatch_exposure()"]
    B --> C["dispatch_exposure(tracker, executor, ...)"]
    C --> D{executor is None?}
    D -- Yes --> E["tracker(...) inline\n(blocking, existing behavior)"]
    D -- No --> F["executor.submit(tracker, ...)"]
    F --> G["future.add_done_callback\n(_log_tracker_future_exception)"]
    G --> H{future exception?}
    H -- Yes --> I["logger.error(...)"]
    H -- No --> J["done"]
    F --> K["return immediately\n(non-blocking)"]

_{Reviews (3): Last reviewed commit: "chore: fix ruff format + move Executor/F..." | Re-trigger Greptile}

…ures executor.submit(...) returned a Future that was immediately discarded, so tracker exceptions raised on the executor thread disappeared with the Future. Added a done_callback that logs future.exception() at ERROR so failures are visible. Also collapsed the two identical _dispatch_exposure methods on LocalFeatureFlagsProvider and RemoteFeatureFlagsProvider into a shared utils.dispatch_exposure helper. Any future change to the dispatch policy (retry, timeout, tracing) now lives in one place. New test test_dispatch_exposure_logs_executor_thread_exceptions locks in the callback behavior — it would fail without add_done_callback.

tylerjroach · 2026-07-02T16:22:51Z

Pushed 34975e5 addressing both Greptile threads.

P2 — silently swallowed tracker exceptions (local_feature_flags.py:529): the new shared helper attaches a add_done_callback that pulls future.exception() and logs it at ERROR (Exposure event failed on executor thread: <type>: <msg>). Otherwise the Future retained the exception and it disappeared silently. New spec test_dispatch_exposure_logs_executor_thread_exceptions locks this in — it fails without the callback.

P2 — _dispatch_exposure duplicated verbatim (remote_feature_flags.py:285): extracted into mixpanel.flags.utils.dispatch_exposure(tracker, executor, distinct_id, properties). Both providers now delegate. Any future change to dispatch policy (retries, tracing, timeouts) lives in one place.

All 89 flag tests pass locally.

Applies ruff format to test_utils.py and utils.py, and moves the annotation-only Executor/Future imports behind TYPE_CHECKING to satisfy TC003.

tylerjroach requested review from a team and jakewski June 30, 2026 17:07

tylerjroach and others added 2 commits June 30, 2026 14:11

chore: ruff format

f810e2f

tylerjroach changed the title ~~fix(analytics): allow capability to offload reportExposure to async thread~~ fix(analytics): allow capability to offload reportExposure to async thread (SDK-80) Jun 30, 2026

greptile-apps Bot reviewed Jul 2, 2026

View reviewed changes

Comment thread mixpanel/flags/local_feature_flags.py Outdated

Comment thread mixpanel/flags/remote_feature_flags.py Outdated

chore: fix ruff format + move Executor/Future to TYPE_CHECKING

8e167f4

Applies ruff format to test_utils.py and utils.py, and moves the annotation-only Executor/Future imports behind TYPE_CHECKING to satisfy TC003.

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fix(analytics): allow capability to offload reportExposure to async thread (SDK-80)#181

fix(analytics): allow capability to offload reportExposure to async thread (SDK-80)#181
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