add(cmd/crm): import monitor

cmd/crm/monitor.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"encoding/json"
+	"expvar"
+	"fmt"
+	"runtime"
+	"time"
+)
+
+type Monitor struct {
+	Alloc,
+	TotalAlloc,
+	Sys,
+	Mallocs,
+	Frees,
+	LiveObjects,
+	PauseTotalNs uint64
+
+	NumGC        uint32
+	NumGoroutine int
+}
+
+func NewMonitor(duration int) {
+	var (
+		m          = Monitor{}
+		rtm        runtime.MemStats
+		goroutines = expvar.NewInt("num_goroutine")
+	)
+	var interval = time.Duration(duration) * time.Second
+	for {
+		<-time.After(interval)
+
+		// Read full mem stats
+		runtime.ReadMemStats(&rtm)
+
+		// Number of goroutines
+		m.NumGoroutine = runtime.NumGoroutine()
+		goroutines.Set(int64(m.NumGoroutine))
+
+		// Misc memory stats
+		m.Alloc = rtm.Alloc
+		m.TotalAlloc = rtm.TotalAlloc
+		m.Sys = rtm.Sys
+		m.Mallocs = rtm.Mallocs
+		m.Frees = rtm.Frees
+
+		// Live objects = Mallocs - Frees
+		m.LiveObjects = m.Mallocs - m.Frees
+
+		// GC Stats
+		m.PauseTotalNs = rtm.PauseTotalNs
+		m.NumGC = rtm.NumGC
+
+		// Just encode to json and print
+		b, _ := json.Marshal(m)
+		fmt.Println(string(b))
+	}
+}