refactor: addition of some golang metrics, cpu, memory, number of gc and time in gc

Author: dimakis

Diff for: cmd/kar-controllers/app/metrics.go

@@ -0,0 +1,48 @@
+package app
+
+import (
+	"runtime"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+    goroutines = promauto.NewGauge(prometheus.GaugeOpts{
+        Name: "mcad_goroutines_total",
+        Help: "Current number of goroutines",
+    })
+    memory = promauto.NewGauge(prometheus.GaugeOpts{
+        Name: "mcad_memory_usage_bytes",
+        Help: "Current memory usage",
+    })
+    gc = promauto.NewCounter(prometheus.CounterOpts{
+        Name: "mcad_gc_operations_total",
+        Help: "Total number of GC operations",
+    })
+    gcTime = promauto.NewCounter(prometheus.CounterOpts{
+        Name: "mcad_gc_time_seconds",
+        Help: "Total time spent in GC",
+    })
+)
+
+func RecordMetrics() {
+    go func() {
+        for {
+            m := &runtime.MemStats{}
+            runtime.ReadMemStats(m)
+
+			// runtime.NumGoroutine() returns the number of goroutines that currently exist
+            goroutines.Set(float64(runtime.NumGoroutine()))
+			//  m.Sys is the total bytes of memory obtained from the OS
+            memory.Set(float64(m.Sys))
+			// m.NumGC is the number of completed GarbageCollection cycles since the program started 
+            gc.Add(float64(m.NumGC))
+			// m.PauseTotalNs is the total GarbageCollection pause time since the program started
+            gcTime.Add(float64(m.PauseTotalNs) / float64(time.Second))
+
+            time.Sleep(2 * time.Second)
+        }
+    }()
+}