November improvements. (#29)

* Tackling the CPU / memory spikes after some time.

* Update admin dashboard, fix the circuit breaker and request coalescing.

monitoring/monitoring.go

@@ -1,6 +1,7 @@
 package libpack_monitoring
 
 import (
+	"context"
 	"flag"
 	"fmt"
 	"time"
@@ -17,6 +18,8 @@ type MetricsSetup struct {
 	metrics_set_custom *metrics.Set
 	ic                 *InitConfig
 	metrics_prefix     string
+	ctx                context.Context
+	cancel             context.CancelFunc
 }
 
 var log = libpack_logger.New().SetMinLogLevel(libpack_logger.LEVEL_INFO)
@@ -27,10 +30,18 @@ type InitConfig struct {
 }
 
 func NewMonitoring(ic *InitConfig) *MetricsSetup {
+	return NewMonitoringWithContext(context.Background(), ic)
+}
+
+// NewMonitoringWithContext creates a new monitoring instance with context for graceful shutdown
+func NewMonitoringWithContext(ctx context.Context, ic *InitConfig) *MetricsSetup {
+	monCtx, cancel := context.WithCancel(ctx)
 	ms := &MetricsSetup{
 		ic:                 ic,
 		metrics_set:        metrics.NewSet(),
 		metrics_set_custom: metrics.NewSet(),
+		ctx:                monCtx,
+		cancel:             cancel,
 	}
 
 	if flag.Lookup("test.v") == nil {
@@ -39,8 +50,14 @@ func NewMonitoring(ic *InitConfig) *MetricsSetup {
 		if ic.PurgeEvery > 0 {
 			ticker := time.NewTicker(time.Duration(ic.PurgeEvery) * time.Second)
 			go func() {
-				for range ticker.C {
-					ms.PurgeMetrics()
+				defer ticker.Stop()
+				for {
+					select {
+					case <-ms.ctx.Done():
+						return
+					case <-ticker.C:
+						ms.PurgeMetrics()
+					}
 				}
 			}()
 		}
@@ -49,6 +66,13 @@ func NewMonitoring(ic *InitConfig) *MetricsSetup {
 	return ms
 }
 
+// Shutdown stops the monitoring goroutines
+func (ms *MetricsSetup) Shutdown() {
+	if ms.cancel != nil {
+		ms.cancel()
+	}
+}
+
 func (ms *MetricsSetup) startPrometheusEndpoint() {
 	app := fiber.New(fiber.Config{
 		DisableStartupMessage: true,
@@ -95,6 +119,20 @@ func (ms *MetricsSetup) RegisterMetricsGauge(metric_name string, labels map[stri
 	})
 }
 
+// RegisterMetricsGaugeFunc registers a gauge with a callback function that is called on every scrape
+// This is useful for metrics that need to return a dynamic value
+func (ms *MetricsSetup) RegisterMetricsGaugeFunc(metric_name string, labels map[string]string, fn func() float64) *metrics.Gauge {
+	if err := validate_metrics_name(metric_name); err != nil {
+		log.Error(&libpack_logger.LogMessage{
+			Message: "RegisterMetricsGaugeFunc() error - invalid metric name",
+			Pairs:   map[string]interface{}{"error": err.Error(), "metric_name": metric_name},
+		})
+		// Return a dummy gauge instead of nil to prevent panics
+		return &metrics.Gauge{}
+	}
+	return ms.metrics_set_custom.GetOrCreateGauge(ms.get_metrics_name(metric_name, labels), fn)
+}
+
 func (ms *MetricsSetup) RegisterMetricsCounter(metric_name string, labels map[string]string) *metrics.Counter {
 	if err := validate_metrics_name(metric_name); err != nil {
 		log.Error(&libpack_logger.LogMessage{