containerd/monitor/monitor_linux.go

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package monitor
import (
"sync"
"syscall"
"github.com/Sirupsen/logrus"
"github.com/docker/containerd/archutils"
)
type Monitorable interface {
FD() int
}
type Flusher interface {
Flush() error
}
// New returns a new process monitor that emits events whenever the
// state of the fd refering to a process changes
func New() (*Monitor, error) {
fd, err := archutils.EpollCreate1(0)
if err != nil {
return nil, err
}
return &Monitor{
epollFd: fd,
receivers: make(map[int]Monitorable),
events: make(chan Monitorable, 1024),
}, nil
}
type Monitor struct {
m sync.Mutex
receivers map[int]Monitorable
events chan Monitorable
epollFd int
}
// Events returns a chan that receives a Monitorable when it's FD changes state
func (m *Monitor) Events() chan Monitorable {
return m.events
}
// Add adds a process to the list of the one being monitored
func (m *Monitor) Add(ma Monitorable) error {
m.m.Lock()
defer m.m.Unlock()
fd := ma.FD()
event := syscall.EpollEvent{
Fd: int32(fd),
Events: syscall.EPOLLHUP,
}
if err := archutils.EpollCtl(m.epollFd, syscall.EPOLL_CTL_ADD, fd, &event); err != nil {
return err
}
m.receivers[fd] = ma
return nil
}
// Remove deletes the Monitorable type from the monitor so that
// no other events are generated
func (m *Monitor) Remove(ma Monitorable) error {
m.m.Lock()
defer m.m.Unlock()
fd := ma.FD()
delete(m.receivers, fd)
return syscall.EpollCtl(m.epollFd, syscall.EPOLL_CTL_DEL, fd, &syscall.EpollEvent{
Events: syscall.EPOLLHUP,
Fd: int32(fd),
})
}
// Close cleans up resources allocated to the Monitor
func (m *Monitor) Close() error {
return syscall.Close(m.epollFd)
}
func (m *Monitor) Run() {
var events [128]syscall.EpollEvent
for {
n, err := archutils.EpollWait(m.epollFd, events[:], -1)
if err != nil {
if err == syscall.EINTR {
continue
}
logrus.WithField("error", err).Fatal("containerd: epoll wait")
}
for i := 0; i < n; i++ {
fd := int(events[i].Fd)
m.m.Lock()
r := m.receivers[fd]
m.m.Unlock()
if f, ok := r.(Flusher); ok {
if err := f.Flush(); err != nil {
logrus.WithField("error", err).Fatal("containerd: flush event FD")
}
}
m.events <- r
}
}
}