feat: add ranked season rollover policy

server/domain/probes.go

@@ -8,16 +8,16 @@ import (
 )
 
 const (
-	ProbeFreshness = 30 * time.Second
-	ProbeFutureSkew = 5 * time.Second
+	ProbeFreshness         = 30 * time.Second
+	ProbeFutureSkew        = 5 * time.Second
 	MaxOpaqueLocationBytes = 512
-	DiscrepancyWindow = 24 * time.Hour
-	DiscrepancyLimit = 3
-	CleanSamplesToRelease = 5
+	DiscrepancyWindow      = 24 * time.Hour
+	DiscrepancyLimit       = 3
+	CleanSamplesToRelease  = 5
 )
 
 var (
-	ErrInvalidProbe = errors.New("invalid latency probe evidence")
+	ErrInvalidProbe     = errors.New("invalid latency probe evidence")
 	ErrProbeQuarantined = errors.New("latency samples are quarantined")
 )
 
@@ -26,10 +26,10 @@ var (
 // no client-provided RTT is used for placement.
 type ProbeEvidence struct {
 	OpaqueLocation []byte
-	Nonce []byte
-	IssuedAt time.Time
-	Region string
-	ServerRTT time.Duration
+	Nonce          []byte
+	IssuedAt       time.Time
+	Region         string
+	ServerRTT      time.Duration
 }
 
 func ValidateProbe(evidence ProbeEvidence, expectedNonce []byte, now time.Time) error {
@@ -52,9 +52,9 @@ func ValidateProbe(evidence ProbeEvidence, expectedNonce []byte, now time.Time)
 }
 
 type DiscrepancyTracker struct {
-	BadSamples []time.Time
+	BadSamples   []time.Time
 	CleanSamples int
-	Quarantined bool
+	Quarantined  bool
 }
 
 // RecordComparison compares backend-computed predicted and observed RTT. A
@@ -65,14 +65,20 @@ func (tracker *DiscrepancyTracker) RecordComparison(predicted, observed time.Dur
 	maxAllowed := 25 * time.Millisecond
 	if predicted > 0 {
 		percent := time.Duration(float64(predicted) * 0.30)
-		if percent > maxAllowed { maxAllowed = percent }
+		if percent > maxAllowed {
+			maxAllowed = percent
+		}
 	}
 	delta := predicted - observed
-	if delta < 0 { delta = -delta }
+	if delta < 0 {
+		delta = -delta
+	}
 	if delta > maxAllowed {
 		tracker.BadSamples = append(tracker.BadSamples, now)
 		tracker.CleanSamples = 0
-		if len(tracker.BadSamples) >= DiscrepancyLimit { tracker.Quarantined = true }
+		if len(tracker.BadSamples) >= DiscrepancyLimit {
+			tracker.Quarantined = true
+		}
 		return
 	}
 	if tracker.Quarantined {
@@ -89,12 +95,16 @@ func (tracker *DiscrepancyTracker) prune(now time.Time) {
 	cutoff := now.Add(-DiscrepancyWindow)
 	kept := tracker.BadSamples[:0]
 	for _, sample := range tracker.BadSamples {
-		if !sample.Before(cutoff) { kept = append(kept, sample) }
+		if !sample.Before(cutoff) {
+			kept = append(kept, sample)
+		}
 	}
 	tracker.BadSamples = kept
 }
 
 func (tracker DiscrepancyTracker) PlacementAllowed() error {
-	if tracker.Quarantined { return ErrProbeQuarantined }
+	if tracker.Quarantined {
+		return ErrProbeQuarantined
+	}
 	return nil
 }