Scrap of a GNUPlot chart

gnuplot_chart.go

// set term png
// set xlabel 'Samples'
// set ylabel 'MB'
// set output 'name.png'
// plot
// 	"name.dat" using 1:($2/1e6) title 'Sys' with lines,
// 	"name.dat" using 1:($3/1e6) title 'Alloc' with lines,
// 	"name.dat" using 1:($4/1e6) title 'Idle' with lines
type chart struct {
	filename string
	file     io.WriteCloser
	samples  int
	m        runtime.MemStats
}

func newChart(name string) *chart {
	filename := name + ".dat"
	os.Remove(filename)
	file, err := os.Create(filename)
	if err != nil {
		panic(err)
	}
	c := &chart{
		filename: filename,
		file:     file,
	}
	c.header()
	return c
}

func (c *chart) header() {
	fmt.Fprint(c.file, "# Samples\tSys\tAlloc\tIdle\tReleased\tGoroutines\n")
}

func (c *chart) Sample() {
	c.samples++
	runtime.ReadMemStats(&c.m)
	fmt.Fprintf(
		c.file,
		"%d\t%d\t%d\t%d\t%d\t%d\n",
		c.samples,
		c.m.HeapSys,
		c.m.HeapAlloc,
		c.m.HeapIdle,
		c.m.HeapReleased,
		runtime.NumGoroutine(),
	)
}

func (c *chart) Close() error {
	return c.file.Close()
}