github.com/fabiokung/docker@v0.11.2-0.20170222101415-4534dcd49497/daemon/stats/collector_unix.go (about)

     1  // +build !windows,!solaris
     2  
     3  package stats
     4  
     5  import (
     6  	"fmt"
     7  	"os"
     8  	"strconv"
     9  	"strings"
    10  
    11  	"github.com/opencontainers/runc/libcontainer/system"
    12  )
    13  
    14  // platformNewStatsCollector performs platform specific initialisation of the
    15  // Collector structure.
    16  func platformNewStatsCollector(s *Collector) {
    17  	s.clockTicksPerSecond = uint64(system.GetClockTicks())
    18  }
    19  
    20  const nanoSecondsPerSecond = 1e9
    21  
    22  // getSystemCPUUsage returns the host system's cpu usage in
    23  // nanoseconds. An error is returned if the format of the underlying
    24  // file does not match.
    25  //
    26  // Uses /proc/stat defined by POSIX. Looks for the cpu
    27  // statistics line and then sums up the first seven fields
    28  // provided. See `man 5 proc` for details on specific field
    29  // information.
    30  func (s *Collector) getSystemCPUUsage() (uint64, error) {
    31  	var line string
    32  	f, err := os.Open("/proc/stat")
    33  	if err != nil {
    34  		return 0, err
    35  	}
    36  	defer func() {
    37  		s.bufReader.Reset(nil)
    38  		f.Close()
    39  	}()
    40  	s.bufReader.Reset(f)
    41  	err = nil
    42  	for err == nil {
    43  		line, err = s.bufReader.ReadString('\n')
    44  		if err != nil {
    45  			break
    46  		}
    47  		parts := strings.Fields(line)
    48  		switch parts[0] {
    49  		case "cpu":
    50  			if len(parts) < 8 {
    51  				return 0, fmt.Errorf("invalid number of cpu fields")
    52  			}
    53  			var totalClockTicks uint64
    54  			for _, i := range parts[1:8] {
    55  				v, err := strconv.ParseUint(i, 10, 64)
    56  				if err != nil {
    57  					return 0, fmt.Errorf("Unable to convert value %s to int: %s", i, err)
    58  				}
    59  				totalClockTicks += v
    60  			}
    61  			return (totalClockTicks * nanoSecondsPerSecond) /
    62  				s.clockTicksPerSecond, nil
    63  		}
    64  	}
    65  	return 0, fmt.Errorf("invalid stat format. Error trying to parse the '/proc/stat' file")
    66  }