feat: on-demand refresh mode - #3
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Background polling assumes the process keeps running between requests. On CPU-throttled / scale-to-zero runtimes (Cloud Run, Lambda between invocations) the timer either doesn't fire or wakes the instance for work nobody asked for. `refresh_mode="on-demand"` (or `CRU_FLAGS_REFRESH_MODE=on-demand`) starts no thread and refreshes on the reading thread when the snapshot is `poll_seconds` or older. Concurrent readers coalesce onto one fetch; staleness is anchored on the last attempt, so a dead service costs one request per interval, not one per read. Also adds `refresh(force=False)`, useful in both modes. Trade-off: in on-demand mode `enabled()` can block for up to `fetch_timeout`, once per interval. Background mode is unchanged and remains the default. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The test service is a ThreadingHTTPServer; its per-request handler thread could still be alive at the assert, failing on CI (3.11/3.12). Co-authored-by: Claude <noreply@anthropic.com>
Full rationale stays in design.md §5.1; README, CLAUDE.md and docstrings keep the contract and point there. Co-authored-by: Claude <noreply@anthropic.com>
mattdrees
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August 4, 2026 16:08
Omicron7
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🤖 I have created a release *beep* *boop* --- ## [0.1.2](v0.1.1...v0.1.2) (2026-08-04) ### Added * on-demand refresh mode ([#3](#3)) ([8f068dd](8f068dd)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
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Adds an
on-demandrefresh mode for runtimes that freeze between requests (Cloud Run, Lambda), per Brian's ask in the feature-flags thread.Client(refresh_mode="on-demand"), orCRU_FLAGS_REFRESH_MODE=on-demandfor a deploy-time switch. Default staysbackground.poll_seconds. Bounded byfetch_timeout; reads still never raise.refresh(force=False)for an explicit poke (useful in both modes).ready()in on-demand performs the first attempt rather than waiting on a thread.Rationale for polling on the request path instead of a wake-up-the-app poller: on scale-to-zero the background timer either doesn't run or keeps the instance warm; a synchronous refresh every
poll_secondsis fast enough and cheaper.