upd(sam): update monitor, add new fields, restructure

cmd/sam/main.go

@@ -30,7 +30,7 @@ func main() {
 
 	// log to stdout not stderr
 	log.SetOutput(os.Stdout)
-	NewMonitor(config.monitorInterval)
+	go NewMonitor(config.monitorInterval)
 
 	// set up database connection
 	factory.Database.Add("default", config.dbDSN)

cmd/sam/monitor.go

@@ -8,40 +8,46 @@ import (
 )
 
 type Monitor struct {
-	runtime.MemStats
+	Alloc,
+	TotalAlloc,
+	Sys,
+	Mallocs,
+	Frees,
+	LiveObjects,
+	PauseTotalNs uint64
+
+	NumGC        uint32
 	NumGoroutine int
 }
 
-func (m Monitor) MarshalJSON() ([]byte, error) {
-	result := struct {
-		Alloc,
-		TotalAlloc,
-		Sys,
-		Mallocs,
-		Frees uint64
-
-		NumGC        uint32
-		NumGoroutine int
-	}{
-		m.MemStats.Alloc,
-		m.MemStats.TotalAlloc,
-		m.MemStats.Sys,
-		m.MemStats.Mallocs,
-		m.MemStats.Frees,
-
-		m.MemStats.NumGC,
-		m.NumGoroutine,
-	}
-	return json.Marshal(result)
-}
-
 func NewMonitor(duration int) {
 	var m Monitor
+	var rtm runtime.MemStats
 	var interval = time.Duration(duration) * time.Second
 	for {
 		<-time.After(interval)
-		runtime.ReadMemStats(&m.MemStats)
+
+		// Read full mem stats
+		runtime.ReadMemStats(&rtm)
+
+		// Number of goroutines
 		m.NumGoroutine = runtime.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))
 	}