Refactor epoll monitor for generic use

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

supervisor/utils.go

@@ -0,0 +1,101 @@
+package supervisor
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/docker/containerd/runtime"
+)
+
+type containerInfo struct {
+	container runtime.Container
+}
+
+func setupEventLog(s *Supervisor, retainCount int) error {
+	if err := readEventLog(s); err != nil {
+		return err
+	}
+	logrus.WithField("count", len(s.eventLog)).Debug("containerd: read past events")
+	events := s.Events(time.Time{}, false, "")
+	return eventLogger(s, filepath.Join(s.config.StateDir, "events.log"), events, retainCount)
+}
+
+func eventLogger(s *Supervisor, path string, events chan Event, retainCount int) error {
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND|os.O_TRUNC, 0755)
+	if err != nil {
+		return err
+	}
+	go func() {
+		var (
+			count = len(s.eventLog)
+			enc   = json.NewEncoder(f)
+		)
+		for e := range events {
+			// if we have a specified retain count make sure the truncate the event
+			// log if it grows past the specified number of events to keep.
+			if retainCount > 0 {
+				if count > retainCount {
+					logrus.Debug("truncating event log")
+					// close the log file
+					if f != nil {
+						f.Close()
+					}
+					slice := retainCount - 1
+					l := len(s.eventLog)
+					if slice >= l {
+						slice = l
+					}
+					s.eventLock.Lock()
+					s.eventLog = s.eventLog[len(s.eventLog)-slice:]
+					s.eventLock.Unlock()
+					if f, err = os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND|os.O_TRUNC, 0755); err != nil {
+						logrus.WithField("error", err).Error("containerd: open event to journal")
+						continue
+					}
+					enc = json.NewEncoder(f)
+					count = 0
+					for _, le := range s.eventLog {
+						if err := enc.Encode(le); err != nil {
+							logrus.WithField("error", err).Error("containerd: write event to journal")
+						}
+					}
+				}
+			}
+			s.eventLock.Lock()
+			s.eventLog = append(s.eventLog, e)
+			s.eventLock.Unlock()
+			count++
+			if err := enc.Encode(e); err != nil {
+				logrus.WithField("error", err).Error("containerd: write event to journal")
+			}
+		}
+	}()
+	return nil
+}
+
+func readEventLog(s *Supervisor) error {
+	f, err := os.Open(filepath.Join(s.config.StateDir, "events.log"))
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	defer f.Close()
+	dec := json.NewDecoder(f)
+	for {
+		var e Event
+		if err := dec.Decode(&e); err != nil {
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+		s.eventLog = append(s.eventLog, e)
+	}
+	return nil
+}