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statsCollector: fix data race in run()

statsCollector.publishers must be protected to prevent
modifications during the iteration in run().
Being locked for a long time is bad, so pairs of containers &
publishers (pointers) are copied to release the lock fast.

Signed-off-by: Anton Tiurin <noxiouz@yandex.ru>
This commit is contained in:
Anton Tiurin 2015-04-24 00:39:05 +03:00
parent b31d154294
commit 11a5f1af01

View file

@ -76,22 +76,42 @@ func (s *statsCollector) unsubscribe(c *Container, ch chan interface{}) {
}
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 {
systemUsage, err := s.getSystemCpuUsage()
if err != nil {
logrus.Errorf("collecting system cpu usage for %s: %v", container.ID, err)
continue
}
stats, err := container.Stats()
// 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", container.ID, err)
logrus.Errorf("collecting stats for %s: %v", pair.container.ID, err)
}
continue
}
stats.SystemUsage = systemUsage
publisher.Publish(stats)
pair.publisher.Publish(stats)
}
}
}