- Introduce `skipOnWindows` helper to properly skip tests relying on Unix specific paths.
- Replace fixed sleep with `require.Eventually` in `waitForPeerDisconnect` to address flakiness in CI.
- Split `commitFastPath` logic out of `runFastPathSync` to close race conditions and improve clarity.
- Update tests to leverage new helpers and more precise assertions (e.g., `waitForPeerDisconnect`).
- Add `flakyStore` test helper to exercise fail-closed behavior in flag handling.
- Enhance `RunFastPathFlagRoutine` to disable the flag on store read errors.
Gate the peer-sync fast path on a runtime flag polled from Redis so operators can roll the optimisation out gradually and flip it off without a redeploy.
Without NB_PEER_SYNC_REDIS_ADDRESS the routine stays disabled, every Sync runs the full network map path, and no entries accumulate in the peer serial cache — bit-for-bit identical to the pre-fast-path behaviour. When the env var is set, a background goroutine polls the configured key (default "peerSyncFastPath") every minute; values "1" or "true" enable the fast path, anything else disables it.
- RunFastPathFlagRoutine mirrors shared/logleveloverrider: dedicated Redis connection, background ticker, redis.Nil treated as disabled.
- NewServer takes the flag handle; tryFastPathSync and the recordPeerSyncEntry helpers short-circuit when Enabled() is false.
- invalidatePeerSyncEntry still runs on Login regardless of flag state.
- NewFastPathFlag(bool) exposed for tests and callers that need to force a state without going through Redis.
Introduce a peer-sync cache keyed by WireGuard pubkey that records the
NetworkMap.Serial and meta hash the server last delivered to each peer.
When a Sync request arrives from a non-Android peer whose cached serial
matches the current account serial and whose meta hash matches the last
delivery, short-circuit SyncAndMarkPeer and reply with a NetbirdConfig-only
SyncResponse mirroring the shape TimeBasedAuthSecretsManager already pushes
for TURN/Relay token rotation. The client keeps its existing network map
state and refreshes only control-plane credentials.
The fast path avoids GetAccountWithBackpressure, the full per-peer map
assembly, posture-check recomputation and the large encrypted payload on
every reconnect of a peer whose account is quiescent. Slow path remains
the source of truth for any real state change; every full-map send (initial
sync or streamed NetworkMap update) rewrites the cache, and every Login
deletes it so a fresh map is guaranteed after SSH key rotation, approval
changes or re-registration.
Backend-only: no proto changes and no client changes. Compatibility is
provided by the existing client handling of nil NetworkMap in handleSync
(every version from v0.20.0 on). Android is gated out at the server because
its readInitialSettings path calls GrpcClient.GetNetworkMap which errors on
nil map. The cache is wired through BaseServer.CacheStore() so it shares
the same Redis/in-memory backend as OneTimeTokenStore and PKCEVerifierStore.
Test coverage lands in four layers:
- Pure decision function (peer_serial_cache_decision_test.go)
- Cache wrapper with TTL + concurrency (peer_serial_cache_test.go)
- Response shape unit tests (sync_fast_path_response_test.go)
- In-process gRPC behavioural tests covering first sync, reconnect skip,
android never-skip, meta change, login invalidation, and serial advance
(management/server/sync_fast_path_test.go)
- Frozen SyncRequest wire-format fixtures for v0.20.0 / v0.40.0 / v0.60.0
/ current / android replayed against the in-process server
(management/server/sync_legacy_wire_test.go + testdata fixtures)
