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oom.go
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oom.go
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// +build linux
package cgroups
import (
"sync"
"golang.org/x/sys/unix"
"github.com/containerd/cgroups"
metrics "github.com/docker/go-metrics"
"github.com/sirupsen/logrus"
)
func NewOOMCollector(ns *metrics.Namespace) (*OOMCollector, error) {
fd, err := unix.EpollCreate1(unix.EPOLL_CLOEXEC)
if err != nil {
return nil, err
}
c := &OOMCollector{
fd: fd,
memoryOOM: ns.NewLabeledGauge("memory_oom", "The number of times a container received an oom event", metrics.Total, "container_id", "namespace"),
set: make(map[uintptr]*oom),
}
go c.start()
return c, nil
}
type OOMCollector struct {
mu sync.Mutex
memoryOOM metrics.LabeledGauge
fd int
set map[uintptr]*oom
}
type oom struct {
id string
namespace string
c cgroups.Cgroup
triggers []Trigger
}
func (o *OOMCollector) Add(id, namespace string, cg cgroups.Cgroup, triggers ...Trigger) error {
o.mu.Lock()
defer o.mu.Unlock()
fd, err := cg.OOMEventFD()
if err != nil {
return err
}
o.set[fd] = &oom{
id: id,
c: cg,
triggers: triggers,
namespace: namespace,
}
// set the gauge's default value
o.memoryOOM.WithValues(id, namespace).Set(0)
event := unix.EpollEvent{
Fd: int32(fd),
Events: unix.EPOLLHUP | unix.EPOLLIN | unix.EPOLLERR,
}
if err := unix.EpollCtl(o.fd, unix.EPOLL_CTL_ADD, int(fd), &event); err != nil {
return err
}
return nil
}
// Close closes the epoll fd
func (o *OOMCollector) Close() error {
return unix.Close(int(o.fd))
}
func (o *OOMCollector) start() {
var events [128]unix.EpollEvent
for {
n, err := unix.EpollWait(o.fd, events[:], -1)
if err != nil {
if err == unix.EINTR {
continue
}
logrus.WithField("error", err).Fatal("cgroups: epoll wait")
}
for i := 0; i < n; i++ {
o.process(uintptr(events[i].Fd), events[i].Events)
}
}
}
func (o *OOMCollector) process(fd uintptr, event uint32) {
// make sure to always flush the fd
flush(fd)
o.mu.Lock()
info, ok := o.set[fd]
if !ok {
o.mu.Unlock()
return
}
o.mu.Unlock()
// if we received an event but it was caused by the cgroup being deleted and the fd
// being closed make sure we close our copy and remove the container from the set
if info.c.State() == cgroups.Deleted {
o.mu.Lock()
delete(o.set, fd)
o.mu.Unlock()
unix.Close(int(fd))
return
}
o.memoryOOM.WithValues(info.id, info.namespace).Inc(1)
for _, t := range info.triggers {
t(info.id, info.c)
}
}
func flush(fd uintptr) error {
buf := make([]byte, 8)
_, err := unix.Read(int(fd), buf)
return err
}