[management] record pat usage metrics (#4888)

management/server/http/middleware/pat_usage_tracker.go

@@ -0,0 +1,87 @@
+package middleware
+
+import (
+	"context"
+	"maps"
+	"sync"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"go.opentelemetry.io/otel/metric"
+)
+
+// PATUsageTracker tracks PAT usage metrics
+type PATUsageTracker struct {
+	usageCounters map[string]int64
+	mu            sync.Mutex
+	stopChan      chan struct{}
+	ctx           context.Context
+	histogram     metric.Int64Histogram
+}
+
+// NewPATUsageTracker creates a new PAT usage tracker with metrics
+func NewPATUsageTracker(ctx context.Context, meter metric.Meter) (*PATUsageTracker, error) {
+	histogram, err := meter.Int64Histogram(
+		"management.pat.usage_distribution",
+		metric.WithUnit("1"),
+		metric.WithDescription("Distribution of PAT token usage counts per minute"),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	tracker := &PATUsageTracker{
+		usageCounters: make(map[string]int64),
+		stopChan:      make(chan struct{}),
+		ctx:           ctx,
+		histogram:     histogram,
+	}
+
+	go tracker.reportLoop()
+
+	return tracker, nil
+}
+
+// IncrementUsage increments the usage counter for a given token
+func (t *PATUsageTracker) IncrementUsage(token string) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.usageCounters[token]++
+}
+
+// reportLoop reports the usage buckets every minute
+func (t *PATUsageTracker) reportLoop() {
+	ticker := time.NewTicker(1 * time.Minute)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			t.reportUsageBuckets()
+		case <-t.stopChan:
+			return
+		}
+	}
+}
+
+// reportUsageBuckets reports all token usage counts and resets counters
+func (t *PATUsageTracker) reportUsageBuckets() {
+	t.mu.Lock()
+	snapshot := maps.Clone(t.usageCounters)
+
+	clear(t.usageCounters)
+	t.mu.Unlock()
+
+	totalTokens := len(snapshot)
+	if totalTokens > 0 {
+		for _, count := range snapshot {
+			t.histogram.Record(t.ctx, count)
+		}
+		log.Debugf("PAT usage in last minute: %d unique tokens used", totalTokens)
+	}
+}
+
+// Stop stops the reporting goroutine
+func (t *PATUsageTracker) Stop() {
+	close(t.stopChan)
+}