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package stats // import "github.com/docker/docker/daemon/stats"
import (
"sync"
"time"
containertypes "github.com/docker/docker/api/types/container"
"github.com/docker/docker/container"
"github.com/moby/pubsub"
)
// Collector manages and provides container resource stats
type Collector struct {
m sync.Mutex
cond *sync.Cond
supervisor supervisor
interval time.Duration
publishers map[*container.Container]*pubsub.Publisher
}
// NewCollector creates a stats collector that will poll the supervisor with the specified interval
func NewCollector(supervisor supervisor, interval time.Duration) *Collector {
s := &Collector{
interval: interval,
supervisor: supervisor,
publishers: make(map[*container.Container]*pubsub.Publisher),
}
s.cond = sync.NewCond(&s.m)
return s
}
type supervisor interface {
// GetContainerStats collects all the stats related to a container
GetContainerStats(container *container.Container) (*containertypes.StatsResponse, error)
}
// 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 *Collector) Collect(c *container.Container) chan interface{} {
s.cond.L.Lock()
defer s.cond.L.Unlock()
publisher, exists := s.publishers[c]
if !exists {
publisher = pubsub.NewPublisher(100*time.Millisecond, 1024)
s.publishers[c] = publisher
}
s.cond.Broadcast()
return publisher.Subscribe()
}
// StopCollection closes the channels for all subscribers and removes
// the container from metrics collection.
func (s *Collector) StopCollection(c *container.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 *Collector) Unsubscribe(c *container.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()
}
// Run starts the collectors and will indefinitely collect stats from the supervisor
func (s *Collector) Run() {
type publishersPair struct {
container *container.Container
publisher *pubsub.Publisher
}
// we cannot determine the capacity here.
// it will grow enough in first iteration
var pairs []publishersPair
for {
s.cond.L.Lock()
for len(s.publishers) == 0 {
s.cond.Wait()
}
// it does not make sense in the first iteration,
// but saves allocations in further iterations
pairs = pairs[:0]
for container, publisher := range s.publishers {
// copy pointers here to release the lock ASAP
pairs = append(pairs, publishersPair{container, publisher})
}
s.cond.L.Unlock()
for _, pair := range pairs {
stats, err := s.supervisor.GetContainerStats(pair.container)
if err != nil {
stats = &containertypes.StatsResponse{
Name: pair.container.Name,
ID: pair.container.ID,
}
}
pair.publisher.Publish(*stats)
}
time.Sleep(s.interval)
}
}
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