fix: Report a distinct User-Agent for the async client - #516
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The async client shipped reusing the sync 'PythonClient/<version>' User-Agent, so LaunchDarkly could not tell async traffic apart from sync. Since sync and async ship in one package, the User-Agent token is the distinguishing signal. Add an ASYNC_USER_AGENT token 'PythonAsyncClient' and thread it through the async request paths (AsyncSSEFactory streaming headers, and the async feature requester, FDv2 polling, and event processor request headers) by parameterizing the shared _base_headers / _headers helpers. Sync behavior is unchanged. Register the new token in .sdk_metadata.json under the existing python-server-sdk entry, since async has no independent package. Implements SDK-2658. The analytics/event name 'python-server-sdk-async' already ships; billing confirmed it does not key off the User-Agent.
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🤖 I have created a release *beep* *boop* --- ## [9.18.0](9.17.0...9.18.0) (2026-09-25) ### Features * Add retry state for RETRY-spec backoff ([#522](#522)) ([e734558](e734558)) * Drive repeating tasks from a delay source ([9abe8cb](9abe8cb)) * Retry indefinitely after a data source failure instead of stopping permanently in FDv1 ([e17e173](e17e173)) * warn that payload filtering has no effect with FDv2 ([#518](#518)) ([296311f](296311f)) * Warn when the SDK is used in a forked process without postfork ([#512](#512)) ([75402e9](75402e9)) ### Bug Fixes * Add async modules to the readthedocs API reference ([#513](#513)) ([f40d3b2](f40d3b2)) * Log the cached-data evaluation warning only once per client ([#520](#520)) ([59ce998](59ce998)) * Read all items when a collection is empty ([#524](#524)) ([1087147](1087147)) * Repeating task wait duration is no longer reduced by a slow callback duration. ([9abe8cb](9abe8cb)) * Report a distinct User-Agent for the async client ([#516](#516)) ([514c467](514c467)) * Warn and use the documented default for an invalid poll interval or initial reconnect delay ([e17e173](e17e173)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). <!-- CURSOR_SUMMARY --> --- > [!NOTE] > **Overview** > This PR **cuts release 9.18.0** by bumping the package version in `pyproject.toml`, `ldclient/version.py`, `.release-please-manifest.json`, and the provenance docs example, and by adding the **9.18.0** section to `CHANGELOG.md`. > > There is **no application code in the diff**—Release Please is packaging work that was already merged. The new changelog highlights **FDv1 data-source resilience** (indefinite retry after failures, RETRY-spec backoff state, repeating tasks driven by a delay source, and sane defaults/warnings for invalid poll/reconnect settings), **operational warnings** (forked process without `postfork`, FDv2 payload filtering), and **fixes** (empty-collection reads, repeating-task timing, one-time cached-data warnings, distinct async `User-Agent`, ReadTheDocs async API docs). > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit eef08a1. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup> <!-- /CURSOR_SUMMARY --> --------- Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Jason Bailey <[email protected]>
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Overview
The async client (
AsyncLDClient) shipped reusing the synchronousPythonClient/<version>User-Agent, so LaunchDarkly cannot distinguish async traffic from sync. Because sync and async ship in the same package, the User-Agent token is the signal that tells them apart.This adds a distinct async token
PythonAsyncClientand threads it through every async request path.Changes
impl/http.py: addSYNC_USER_AGENT/ASYNC_USER_AGENTconstants;_base_headers(config, user_agent=SYNC_USER_AGENT).impl/util.py:_headers(config, user_agent=SYNC_USER_AGENT)passes the token through.ASYNC_USER_AGENT:impl/aio/transport.py—AsyncSSEFactorystreaming headersimpl/datasource/async_feature_requester.pyimpl/datasourcev2/async_polling.pyimpl/events/async_event_processor.py.sdk_metadata.json: register the token on the existingpython-server-sdkentry →userAgents: ["PythonClient", "PythonAsyncClient"].Sync behavior is unchanged (the default token is still
PythonClient).Design note
SDK-2658 originally proposed a separate
python-server-sdk-asyncsdk-meta registry entry. We chose to keep a single entry and add the async token to itsuserAgentsarray instead, because async has no independent package and is not a separately-tracked feature.The analytics/event SDK name
python-server-sdk-asyncalready ships (async_client.py); billing confirmed it does not key off the User-Agent, so this change is safe and additive.Tests
New
testing/impl/test_user_agent.pylocks the exact wire tokens for both sync and async via_base_headers/_headers.mypy/isort/pycodestyleclean; touched-component suites pass.Implements SDK-2658.
Note
Overview
Async
AsyncLDClienttraffic previously used the samePythonClient/<version>User-Agent as the sync client, so LaunchDarkly could not tell them apart in one package. This PR introducesPythonAsyncClientand wires it through shared header helpers while keeping sync defaults unchanged.SYNC_USER_AGENT/ASYNC_USER_AGENTare defined inimpl/http.py;_base_headersand_headerstake an optionaluser_agent(defaultPythonClient). Async paths passASYNC_USER_AGENT: SSE inimpl/aio/transport.py, FDv1 polling inasync_feature_requester.py, FDv2 polling inasync_polling.py, and event posts inasync_event_processor.py..sdk_metadata.jsonaddsPythonAsyncClientto the existingpython-server-sdkuserAgentslist.testing/impl/test_user_agent.pyasserts the exact wire User-Agent strings for sync and async.Reviewed by Cursor Bugbot for commit 32498ce. Bugbot is set up for automated code reviews on this repo. Configure here.