moby--moby/daemon/stats_collector.go

package daemon

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	log "github.com/Sirupsen/logrus"
	"github.com/docker/docker/daemon/execdriver"
)

func newStatsCollector(interval time.Duration) *statsCollector {
	s := &statsCollector{
		interval:   interval,
		containers: make(map[string]*statsCollectorData),
	}
	s.start()
	return s
}

type statsCollectorData struct {
	c         *Container
	lastStats *execdriver.ResourceStats
	subs      []chan *execdriver.ResourceStats
}

// statsCollector manages and provides container resource stats
type statsCollector struct {
	m          sync.Mutex
	interval   time.Duration
	containers map[string]*statsCollectorData
}

func (s *statsCollector) collect(c *Container) <-chan *execdriver.ResourceStats {
	s.m.Lock()
	ch := make(chan *execdriver.ResourceStats, 1024)
	s.containers[c.ID] = &statsCollectorData{
		c: c,
		subs: []chan *execdriver.ResourceStats{
			ch,
		},
	}
	s.m.Unlock()
	return ch
}

func (s *statsCollector) stopCollection(c *Container) {
	s.m.Lock()
	delete(s.containers, c.ID)
	s.m.Unlock()
}

func (s *statsCollector) start() {
	go func() {
		for _ = range time.Tick(s.interval) {
			log.Debugf("starting collection of container stats")
			s.m.Lock()
			for id, d := range s.containers {
				systemUsage, err := getSystemCpuUsage()
				if err != nil {
					log.Errorf("collecting system cpu usage for %s: %v", id, err)
					continue
				}
				stats, err := d.c.Stats()
				if err != nil {
					// TODO: @crosbymichael evict container depending on error
					log.Errorf("collecting stats for %s: %v", id, err)
					continue
				}
				stats.SystemUsage = systemUsage
				for _, sub := range s.containers[id].subs {
					sub <- stats
				}
			}
			s.m.Unlock()
		}
	}()
}

// returns value in nanoseconds
func getSystemCpuUsage() (uint64, error) {
	f, err := os.Open("/proc/stat")
	if err != nil {
		return 0, err
	}
	defer f.Close()

	sc := bufio.NewScanner(f)
	for sc.Scan() {
		parts := strings.Fields(sc.Text())
		switch parts[0] {
		case "cpu":
			if len(parts) < 8 {
				return 0, fmt.Errorf("invalid number of cpu fields")
			}

			var total uint64
			for _, i := range parts[1:8] {
				v, err := strconv.ParseUint(i, 10, 64)
				if err != nil {
					return 0.0, fmt.Errorf("Unable to convert value %s to int: %s", i, err)
				}
				total += v
			}
			return total * 1000000000, nil
		default:
			continue
		}
	}
	return 0, fmt.Errorf("invalid stat format")
}