gupta/gupta.go

package gupta

import (
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
	"time"
)

const version = "0.0.1"

func Hello() string {
	return fmt.Sprintf("Welcome to gupta version %s", version)
}

type GuptaReport struct {
	Time        time.Time
	LoadAvarage float64
	CPUUsage    *CPUStat `json:"cpu usage, omitempty"`
	MemoryUsage *Memory  `json:"memory,omitempty"`
}

// usually you'd want a g GuptaReport reciever here ...
// but than you could now check for the object properties ...
func (g *GuptaReport) MarshalJSON() ([]byte, error) {
	report := []byte(fmt.Sprintf("{\"timestamp\": \"%d\", \"metrics\": [",
		g.Time.Unix()))
	if g.CPUUsage != nil {
		usage, _ := json.Marshal(g.CPUUsage)
		report = append(report, usage...)
	}

	if g.MemoryUsage != nil {
		if g.CPUUsage != nil {
			report = append(report, []byte(",")...)
		}
		usage, _ := json.Marshal(g.MemoryUsage)
		report = append(report, usage...)
	}

	report = append(report, []byte("]}")...)
	return report, nil
}

// collect all CPU stat from /proc/cpustat
type CPUStat struct {
	totalTime    float64
	idleTime     float64
	totalTimeNew float64
	idleTimeNew  float64
}

func (c *CPUStat) ReadInfoNew(statline string) {
	rawInfo := strings.Fields(statline)
	idleNew, _ := strconv.ParseFloat(rawInfo[4], 10)
	iowaitNew, _ := strconv.ParseFloat(rawInfo[5], 10)
	c.idleTimeNew = idleNew + iowaitNew
	for _, s := range rawInfo {
		u, _ := strconv.ParseFloat(s, 10)
		c.totalTimeNew += u
	}
}

func (c *CPUStat) ReadInfo(statline string) {
	rawInfo := strings.Fields(statline)
	for _, s := range rawInfo[1:] {
		u, _ := strconv.ParseFloat(s, 10)
		c.totalTime += u
	}
	idle, _ := strconv.ParseFloat(rawInfo[4], 10)
	iowait, _ := strconv.ParseFloat(rawInfo[5], 10)
	c.idleTime = idle + iowait
}

func (c *CPUStat) CPUUsage() float64 {
	deltaIdleTime := c.idleTimeNew - c.idleTime
	deltaTotalTime := c.totalTimeNew - c.totalTime
	cpuUsage := (1.0 - float64(deltaIdleTime)/float64(deltaTotalTime)) * 100
	return cpuUsage
}

func NewCPUStat(procstatline, procstatlineNew string) CPUStat {
	cpustat := CPUStat{}

	cpustat.ReadInfo(procstatline)
	cpustat.ReadInfoNew(procstatlineNew)
	return cpustat
}

func (c CPUStat) MarshalJSON() ([]byte, error) {
	jsonData := []byte(
		fmt.Sprintf("{\"cpu usage\": \"%.2f%%\"}", c.CPUUsage()))
	return jsonData, nil
}