The v1.0.14 fix replaced one contended sync.RWMutex (RefreshCoordinator.
refreshMutex) with sync.Map. Production showed the same death-spiral
signature recurring ~2 hours later — same shape, different mutex:
65 goroutines stuck on a sync.(*RWMutex).Lock at one address, pod
pinned at 1000m CPU, identical Yaegi runCfg/reflect.Value.Call stack
pattern. The mutex was RefreshCoordinator.attemptsMutex.
Generalising: under Yaegi (interpreted Go for traefik plugins), any
per-request global mutex acquisition is a latent serialization point.
reflect.Value.Call dispatch on a held lock turns a microsecond
critical section into a multi-millisecond one, and on a GOMAXPROCS=1
pod the queue is unbounded.
This commit removes every per-request global mutex on the hot path:
1. RefreshCoordinator.attemptsMutex (sync.RWMutex)
sessionRefreshAttempts: map -> sync.Map.
refreshAttemptTracker: all fields atomic (int32, int64 UnixNano,
cooldownEndNano == 0 as the not-in-cooldown sentinel, replacing
the inCooldown bool).
isInCooldown / recordRefreshAttempt / recordRefreshSuccess /
recordRefreshFailure all become lock-free. Cooldown entry uses
CompareAndSwapInt64 so only one goroutine logs the transition.
2. RefreshCircuitBreaker.mutex (sync.RWMutex)
lastFailureTime / lastSuccessTime -> atomic.Int64 UnixNano.
state and failures already atomic.
AllowRequest / RecordSuccess / RecordFailure now pure atomic ops.
3. TraefikOidc.firstRequestMutex (sync.Mutex)
firstRequestReceived bool -> firstRequestStarted int32.
metadataRefreshStarted bool -> metadataRefreshStartedAtomic int32.
ServeHTTP bootstrap path uses CompareAndSwapInt32 — fires once,
zero steady-state cost. Previously the mutex was acquired on
every non-health request forever.
4. TraefikOidc.metadataRetryMutex (sync.Mutex)
lastMetadataRetryTime time.Time -> lastMetadataRetryNano int64.
The 30-second retry throttle is now a CAS on lastMetadataRetryNano.
cleanupStaleEntries iterates via sync.Map.Range; eviction is a
CompareAndDelete by pointer identity so a tracker freshly re-used by
a concurrent caller is not lost.
Empirical evidence (3 specialist-agent analysis of the v1.0.14 spike,
profiles in /tmp/traefik-spike-1779511683/):
* mutex profile: 97% delay in sync.(*Mutex).Unlock via
HTTPHandlerSwitcher -> accesslog -> metrics -> backoff.RetryNotify
* 65 stuck goroutines at one RWMutex address (0x40022eb648),
identical Yaegi CFG pointer, all on rc.attemptsMutex via
recordRefreshAttempt + isInCooldown
* traffic driver: long-lived in-cluster Go-http-client doing
~5.4 req/s POST embeddings via OIDC cookie session → same
sessionID → contention all funnels to one tracker entry
Yaegi support for sync/atomic confirmed at
github.com/traefik/yaegi@v0.16.1/stdlib/go1_22_sync_atomic.go:
AddInt32/Int64, LoadInt32/Int64, StoreInt32/Int64,
CompareAndSwapInt32/Int64 all exposed via reflect.ValueOf. Yaegi
dispatches each call through reflect.Value.Call to the COMPILED
atomic.* function, which executes a single hardware CAS/LOCK-XADD
instruction. Each atomic op still pays Yaegi dispatch cost but
cannot block — no queueing, no death spiral.
Trade-off acknowledged: v1.0.15 issues ~6-8 atomic/sync.Map ops per
leader-path request vs the 4 mutex ops of v1.0.14. Under low
contention this is a modest CPU bump. Under high contention it's
an unbounded → bounded transformation. Net win.
All tests pass with -race; golangci-lint clean.
* Automatic discovery of the scopes.
Issue #61 raised very valid concerns about users configuring scopes that are not supported by the provider.
This change introduces automatic discovery of supported scopes by fetching the provider's discovery document and filtering out unsupported scopes.
Before:
User configures: scopes: ["openid", "profile", "email", "offline_access"]
Self-hosted GitLab: "The requested scope is invalid, unknown, or malformed"
Authentication: ❌ FAILS
After:
User configures: scopes: ["openid", "profile", "email", "offline_access"]
Middleware checks discovery doc → offline_access not supported
Automatically filters to: ["openid", "profile", "email"]
Authentication: ✅ SUCCEEDS
* Resolves issue #74 by enabling user to specify expected audience in the configuration.
* Fix flaky tests.
lukaszraczylo