Fix atomic sync gates - #1020
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July 8, 2026 18:42
The bare rescue in synced_adapter only cleared @syncing for StandardError, so a non-StandardError from the Synchronizer (Interrupt, SignalException, etc.) would leave @syncing true permanently, deadlocking all subsequent reads waiting on @sync_condition. Use an ensure with a synced flag so state is always cleared, bumping @last_synced_at only on success. Mirrors the ensure-based cleanup already in IntervalSynchronizer#call. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Threads that lose the sync claim now return the local adapter immediately instead of waiting on the syncing thread. The data they serve is at most one poll interval stale, which is the contract already, and strictly better than the pre-fix behavior where they read partially applied mid-sync state. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Use PID-scoped atomic gate state so forked child threads converge on one claim, keep Poll losers nonblocking with a coherent pre-sync snapshot, and cover contention and failure recovery paths.
Retain stable Ruby mutexes across fork, reset only process-owned state under lock, and preserve nonblocking interval and trusted-snapshot behavior. Add real-fork regression coverage for Memory, Poller, Poll, and IntervalSynchronizer.
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Fixes thundering-herd syncs caused by unsynchronized check-then-act gates in the poll and interval synchronizers. The poll adapter now coordinates in-flight local updates, retries after failed synchronization, and resets sync state after forks; the interval synchronizer now claims each elapsed interval atomically. This keeps concurrent request threads from issuing duplicate remote reads and overlapping local writes for the same sync window. Validated with
bundle exec rspec spec/flipper/adapters/poll_spec.rb spec/flipper/adapters/sync/interval_synchronizer_spec.rbandbundle exec rspec spec/flipper/adapters, which passed with the existing 2 sqlite pending examples.