Add metrics history memory regression test

internal/monitoring/metrics_history_memory_regression_test.go

@@ -0,0 +1,54 @@
+package monitoring
+
+import (
+	"runtime"
+	"runtime/debug"
+	"testing"
+	"time"
+)
+
+func TestMetricsHistoryMemoryStability(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping memory regression in short mode")
+	}
+
+	history := NewMetricsHistory(64, time.Minute)
+	warmupIterations := 50
+	measureIterations := 200
+
+	seed := func(iter int) {
+		now := time.Now()
+		value := float64(iter % 100)
+		history.AddGuestMetric("guest-1", "memory", value, now)
+		history.AddGuestMetric("guest-1", "cpu", value, now)
+		history.AddNodeMetric("node-1", "memory", value, now)
+		history.AddStorageMetric("storage-1", "usage", value, now)
+		history.Cleanup()
+	}
+
+	for i := 0; i < warmupIterations; i++ {
+		seed(i)
+	}
+
+	runtime.GC()
+	debug.FreeOSMemory()
+	var baseline runtime.MemStats
+	runtime.ReadMemStats(&baseline)
+
+	for i := 0; i < measureIterations; i++ {
+		seed(i)
+	}
+
+	runtime.GC()
+	debug.FreeOSMemory()
+	var after runtime.MemStats
+	runtime.ReadMemStats(&after)
+
+	if baseline.HeapAlloc > 0 {
+		allowed := baseline.HeapAlloc + 5*1024*1024
+		growthRatio := float64(after.HeapAlloc) / float64(baseline.HeapAlloc)
+		if after.HeapAlloc > allowed && growthRatio > 1.25 {
+			t.Fatalf("heap allocation grew too much: baseline=%d final=%d ratio=%.2f", baseline.HeapAlloc, after.HeapAlloc, growthRatio)
+		}
+	}
+}