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moby--moby/daemon/stats_collector.go
unclejack 25f776451e daemon/stats_collector: refactor getSystemCpuUsage
Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com>
2015-05-15 12:22:50 +03:00

160 lines
4 KiB
Go

package daemon
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
"sync"
"time"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/daemon/execdriver"
"github.com/docker/docker/pkg/pubsub"
"github.com/docker/libcontainer/system"
)
// newStatsCollector returns a new statsCollector that collections
// network and cgroup stats for a registered container at the specified
// interval. The collector allows non-running containers to be added
// and will start processing stats when they are started.
func newStatsCollector(interval time.Duration) *statsCollector {
s := &statsCollector{
interval: interval,
publishers: make(map[*Container]*pubsub.Publisher),
clockTicks: uint64(system.GetClockTicks()),
bufReader: bufio.NewReaderSize(nil, 128),
}
go s.run()
return s
}
// statsCollector manages and provides container resource stats
type statsCollector struct {
m sync.Mutex
interval time.Duration
clockTicks uint64
publishers map[*Container]*pubsub.Publisher
bufReader *bufio.Reader
}
// collect registers the container with the collector and adds it to
// the event loop for collection on the specified interval returning
// a channel for the subscriber to receive on.
func (s *statsCollector) collect(c *Container) chan interface{} {
s.m.Lock()
defer s.m.Unlock()
publisher, exists := s.publishers[c]
if !exists {
publisher = pubsub.NewPublisher(100*time.Millisecond, 1024)
s.publishers[c] = publisher
}
return publisher.Subscribe()
}
// stopCollection closes the channels for all subscribers and removes
// the container from metrics collection.
func (s *statsCollector) stopCollection(c *Container) {
s.m.Lock()
if publisher, exists := s.publishers[c]; exists {
publisher.Close()
delete(s.publishers, c)
}
s.m.Unlock()
}
// unsubscribe removes a specific subscriber from receiving updates for a container's stats.
func (s *statsCollector) unsubscribe(c *Container, ch chan interface{}) {
s.m.Lock()
publisher := s.publishers[c]
if publisher != nil {
publisher.Evict(ch)
if publisher.Len() == 0 {
delete(s.publishers, c)
}
}
s.m.Unlock()
}
func (s *statsCollector) run() {
type publishersPair struct {
container *Container
publisher *pubsub.Publisher
}
// we cannot determine the capacity here.
// it will grow enough in first iteration
var pairs []publishersPair
for range time.Tick(s.interval) {
systemUsage, err := s.getSystemCpuUsage()
if err != nil {
logrus.Errorf("collecting system cpu usage: %v", err)
continue
}
// it does not make sense in the first iteration,
// but saves allocations in further iterations
pairs = pairs[:0]
s.m.Lock()
for container, publisher := range s.publishers {
// copy pointers here to release the lock ASAP
pairs = append(pairs, publishersPair{container, publisher})
}
s.m.Unlock()
for _, pair := range pairs {
stats, err := pair.container.Stats()
if err != nil {
if err != execdriver.ErrNotRunning {
logrus.Errorf("collecting stats for %s: %v", pair.container.ID, err)
}
continue
}
stats.SystemUsage = systemUsage
pair.publisher.Publish(stats)
}
}
}
const nanoSeconds = 1e9
// getSystemCpuUSage returns the host system's cpu usage in nanoseconds
// for the system to match the cgroup readings are returned in the same format.
func (s *statsCollector) getSystemCpuUsage() (uint64, error) {
var line string
f, err := os.Open("/proc/stat")
if err != nil {
return 0, err
}
defer func() {
s.bufReader.Reset(nil)
f.Close()
}()
s.bufReader.Reset(f)
err = nil
for err == nil {
line, err = s.bufReader.ReadString('\n')
if err != nil {
break
}
parts := strings.Fields(line)
switch parts[0] {
case "cpu":
if len(parts) < 8 {
return 0, fmt.Errorf("invalid number of cpu fields")
}
var sum uint64
for _, i := range parts[1:8] {
v, err := strconv.ParseUint(i, 10, 64)
if err != nil {
return 0, fmt.Errorf("Unable to convert value %s to int: %s", i, err)
}
sum += v
}
return (sum * nanoSeconds) / s.clockTicks, nil
}
}
return 0, fmt.Errorf("invalid stat format")
}