vendor/github.com/docker/docker/cli/command/container/stats_helpers.go

package container

import (
	"encoding/json"
	"errors"
	"io"
	"strings"
	"sync"
	"time"

	"github.com/Sirupsen/logrus"
	"github.com/docker/docker/api/types"
	"github.com/docker/docker/cli/command/formatter"
	"github.com/docker/docker/client"
	"golang.org/x/net/context"
)

type stats struct {
	ostype string
	mu     sync.Mutex
	cs     []*formatter.ContainerStats
}

// daemonOSType is set once we have at least one stat for a container
// from the daemon. It is used to ensure we print the right header based
// on the daemon platform.
var daemonOSType string

func (s *stats) add(cs *formatter.ContainerStats) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	if _, exists := s.isKnownContainer(cs.Container); !exists {
		s.cs = append(s.cs, cs)
		return true
	}
	return false
}

func (s *stats) remove(id string) {
	s.mu.Lock()
	if i, exists := s.isKnownContainer(id); exists {
		s.cs = append(s.cs[:i], s.cs[i+1:]...)
	}
	s.mu.Unlock()
}

func (s *stats) isKnownContainer(cid string) (int, bool) {
	for i, c := range s.cs {
		if c.Container == cid {
			return i, true
		}
	}
	return -1, false
}

func collect(ctx context.Context, s *formatter.ContainerStats, cli client.APIClient, streamStats bool, waitFirst *sync.WaitGroup) {
	logrus.Debugf("collecting stats for %s", s.Container)
	var (
		getFirst       bool
		previousCPU    uint64
		previousSystem uint64
		u              = make(chan error, 1)
	)

	defer func() {
		// if error happens and we get nothing of stats, release wait group whatever
		if !getFirst {
			getFirst = true
			waitFirst.Done()
		}
	}()

	response, err := cli.ContainerStats(ctx, s.Container, streamStats)
	if err != nil {
		s.SetError(err)
		return
	}
	defer response.Body.Close()

	dec := json.NewDecoder(response.Body)
	go func() {
		for {
			var (
				v                 *types.StatsJSON
				memPercent        = 0.0
				cpuPercent        = 0.0
				blkRead, blkWrite uint64 // Only used on Linux
				mem               = 0.0
				memLimit          = 0.0
				memPerc           = 0.0
				pidsStatsCurrent  uint64
			)

			if err := dec.Decode(&v); err != nil {
				dec = json.NewDecoder(io.MultiReader(dec.Buffered(), response.Body))
				u <- err
				if err == io.EOF {
					break
				}
				time.Sleep(100 * time.Millisecond)
				continue
			}

			daemonOSType = response.OSType

			if daemonOSType != "windows" {
				// MemoryStats.Limit will never be 0 unless the container is not running and we haven't
				// got any data from cgroup
				if v.MemoryStats.Limit != 0 {
					memPercent = float64(v.MemoryStats.Usage) / float64(v.MemoryStats.Limit) * 100.0
				}
				previousCPU = v.PreCPUStats.CPUUsage.TotalUsage
				previousSystem = v.PreCPUStats.SystemUsage
				cpuPercent = calculateCPUPercentUnix(previousCPU, previousSystem, v)
				blkRead, blkWrite = calculateBlockIO(v.BlkioStats)
				mem = float64(v.MemoryStats.Usage)
				memLimit = float64(v.MemoryStats.Limit)
				memPerc = memPercent
				pidsStatsCurrent = v.PidsStats.Current
			} else {
				cpuPercent = calculateCPUPercentWindows(v)
				blkRead = v.StorageStats.ReadSizeBytes
				blkWrite = v.StorageStats.WriteSizeBytes
				mem = float64(v.MemoryStats.PrivateWorkingSet)
			}
			netRx, netTx := calculateNetwork(v.Networks)
			s.SetStatistics(formatter.StatsEntry{
				Name:             v.Name,
				ID:               v.ID,
				CPUPercentage:    cpuPercent,
				Memory:           mem,
				MemoryPercentage: memPerc,
				MemoryLimit:      memLimit,
				NetworkRx:        netRx,
				NetworkTx:        netTx,
				BlockRead:        float64(blkRead),
				BlockWrite:       float64(blkWrite),
				PidsCurrent:      pidsStatsCurrent,
			})
			u <- nil
			if !streamStats {
				return
			}
		}
	}()
	for {
		select {
		case <-time.After(2 * time.Second):
			// zero out the values if we have not received an update within
			// the specified duration.
			s.SetErrorAndReset(errors.New("timeout waiting for stats"))
			// if this is the first stat you get, release WaitGroup
			if !getFirst {
				getFirst = true
				waitFirst.Done()
			}
		case err := <-u:
			if err != nil {
				s.SetError(err)
				continue
			}
			s.SetError(nil)
			// if this is the first stat you get, release WaitGroup
			if !getFirst {
				getFirst = true
				waitFirst.Done()
			}
		}
		if !streamStats {
			return
		}
	}
}

func calculateCPUPercentUnix(previousCPU, previousSystem uint64, v *types.StatsJSON) float64 {
	var (
		cpuPercent = 0.0
		// calculate the change for the cpu usage of the container in between readings
		cpuDelta = float64(v.CPUStats.CPUUsage.TotalUsage) - float64(previousCPU)
		// calculate the change for the entire system between readings
		systemDelta = float64(v.CPUStats.SystemUsage) - float64(previousSystem)
	)

	if systemDelta > 0.0 && cpuDelta > 0.0 {
		cpuPercent = (cpuDelta / systemDelta) * float64(len(v.CPUStats.CPUUsage.PercpuUsage)) * 100.0
	}
	return cpuPercent
}

func calculateCPUPercentWindows(v *types.StatsJSON) float64 {
	// Max number of 100ns intervals between the previous time read and now
	possIntervals := uint64(v.Read.Sub(v.PreRead).Nanoseconds()) // Start with number of ns intervals
	possIntervals /= 100                                         // Convert to number of 100ns intervals
	possIntervals *= uint64(v.NumProcs)                          // Multiple by the number of processors

	// Intervals used
	intervalsUsed := v.CPUStats.CPUUsage.TotalUsage - v.PreCPUStats.CPUUsage.TotalUsage

	// Percentage avoiding divide-by-zero
	if possIntervals > 0 {
		return float64(intervalsUsed) / float64(possIntervals) * 100.0
	}
	return 0.00
}

func calculateBlockIO(blkio types.BlkioStats) (blkRead uint64, blkWrite uint64) {
	for _, bioEntry := range blkio.IoServiceBytesRecursive {
		switch strings.ToLower(bioEntry.Op) {
		case "read":
			blkRead = blkRead + bioEntry.Value
		case "write":
			blkWrite = blkWrite + bioEntry.Value
		}
	}
	return
}

func calculateNetwork(network map[string]types.NetworkStats) (float64, float64) {
	var rx, tx float64

	for _, v := range network {
		rx += float64(v.RxBytes)
		tx += float64(v.TxBytes)
	}
	return rx, tx
}