Add prometheus container level metrics

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

vendor/github.com/crosbymichael/cgroups/prometheus/oom.go

@@ -0,0 +1,110 @@
+package prometheus
+
+import (
+	"sync"
+	"syscall"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/crosbymichael/cgroups"
+	metrics "github.com/docker/go-metrics"
+)
+
+func NewOOMCollector(ns *metrics.Namespace) (*OOMCollector, error) {
+	fd, err := syscall.EpollCreate1(syscall.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, "id"),
+		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
+	c  cgroups.Cgroup
+}
+
+func (o *OOMCollector) Add(id string, cg cgroups.Cgroup) 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,
+	}
+	// set the gauge's default value
+	o.memoryOOM.WithValues(id).Set(0)
+	event := syscall.EpollEvent{
+		Fd:     int32(fd),
+		Events: syscall.EPOLLHUP | syscall.EPOLLIN | syscall.EPOLLERR,
+	}
+	if err := syscall.EpollCtl(o.fd, syscall.EPOLL_CTL_ADD, int(fd), &event); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Close closes the epoll fd
+func (o *OOMCollector) Close() error {
+	return syscall.Close(int(o.fd))
+}
+
+func (o *OOMCollector) start() {
+	var events [128]syscall.EpollEvent
+	for {
+		n, err := syscall.EpollWait(o.fd, events[:], -1)
+		if err != nil {
+			if err == syscall.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()
+		syscall.Close(int(fd))
+		return
+	}
+	o.memoryOOM.WithValues(info.id).Inc(1)
+}
+
+func flush(fd uintptr) error {
+	buf := make([]byte, 8)
+	_, err := syscall.Read(int(fd), buf)
+	return err
+}