add journald support

Author: adohe

Godeps/Godeps.json

@@ -17,15 +17,20 @@ limitations under the License.
 package kernelmonitor
 
 import (
+	"bufio"
+	"bytes"
+	"io"
 	"os"
+	"strings"
 	"time"
 
 	"k8s.io/node-problem-detector/pkg/kernelmonitor/translator"
 	"k8s.io/node-problem-detector/pkg/kernelmonitor/types"
 	"k8s.io/node-problem-detector/pkg/kernelmonitor/util"
 
+	"github.com/coreos/go-systemd/sdjournal"
 	"github.com/golang/glog"
-	"github.com/hpcloud/tail"
+	"github.com/google/cadvisor/utils/tail"
 	utilclock "github.com/pivotal-golang/clock"
 )
 
@@ -54,12 +59,12 @@ type KernelLogWatcher interface {
 
 type kernelLogWatcher struct {
 	// trans is the translator translates the log into internal format.
-	trans translator.Translator
-	cfg   WatcherConfig
-	tl    *tail.Tail
-	logCh chan *types.KernelLog
-	tomb  *util.Tomb
-	clock utilclock.Clock
+	trans  translator.Translator
+	cfg    WatcherConfig
+	reader *bufio.Reader
+	logCh  chan *types.KernelLog
+	tomb   *util.Tomb
+	clock  utilclock.Clock
 }
 
 // NewKernelLogWatcher creates a new kernel log watcher.
@@ -88,25 +93,17 @@ func (k *kernelLogWatcher) Watch() (<-chan *types.KernelLog, error) {
 	// To avoid this, we decide to add this temporarily hack. When KernelMonitor can't find the kernel
 	// log file, it will print a log and then return nil channel and no error. Since nil channel will
 	// always be blocked, the NodeProblemDetector will block forever.
-	// TODO(random-liu):
-	// 1. Add journald supports to support GCI.
-	// 2. Schedule KernelMonitor only on supported node (with node label and selector)
 	if _, err := os.Stat(path); os.IsNotExist(err) {
 		glog.Infof("kernel log %q is not found, kernel monitor doesn't support the os distro", path)
 		return nil, nil
 	}
 	// TODO(random-liu): Rate limit tail file.
-	// TODO(random-liu): Figure out what happens if log lines are removed.
 	// Notice that, kernel log watcher doesn't look back to the rolled out logs.
-	var err error
-	k.tl, err = tail.TailFile(path, tail.Config{
-		Poll:   true,
-		ReOpen: true,
-		Follow: true,
-	})
+	reader, err := getLogReader(path)
 	if err != nil {
 		return nil, err
 	}
+	k.reader = bufio.NewReader(reader)
 	glog.Info("Start watching kernel log")
 	go k.watchLoop()
 	return k.logCh, nil
@@ -126,15 +123,31 @@ func (k *kernelLogWatcher) watchLoop() {
 	if err != nil {
 		glog.Fatalf("failed to parse duration %q: %v", k.cfg.Lookback, err)
 	}
+	var buffer bytes.Buffer
 	for {
+
 		select {
-		case line := <-k.tl.Lines:
-			// Notice that tail has trimmed '\n'
-			if line.Err != nil {
-				glog.Errorf("Tail error: %v", line.Err)
-				continue
-			}
-			log, err := k.trans.Translate(line.Text)
+		case <-k.tomb.Stopping():
+			glog.Infof("Stop watching kernel log")
+			return
+		default:
+		}
+
+		line, err := k.reader.ReadString('\n')
+		if err != nil && err != io.EOF {
+			glog.Errorf("exiting kernel log watch with error: %v", err)
+			return
+		}
+		if line == "" {
+			time.Sleep(100 * time.Millisecond)
+			continue
+		}
+		if err == nil {
+			buffer.WriteString(line)
+			// trime `\n`
+			line = strings.TrimRight(buffer.String(), "\n")
+			buffer.Reset()
+			log, err := k.trans.Translate(line)
 			if err != nil {
 				glog.Infof("Unable to parse line: %q, %v", line, err)
 				continue
@@ -144,14 +157,54 @@ func (k *kernelLogWatcher) watchLoop() {
 				continue
 			}
 			k.logCh <- log
-		case <-k.tomb.Stopping():
-			k.tl.Stop()
-			glog.Infof("Stop watching kernel log")
-			return
+		} else { // err == io.EOF
+			buffer.WriteString(line)
 		}
 	}
 }
 
+// getLogReader gets a kernel log reader.
+func getLogReader(path string) (io.Reader, error) {
+	reader, err := tryJournal()
+	if err == nil {
+		return reader, nil
+	}
+	reader, err = tryLogFile(path)
+	if err == nil {
+		return reader, nil
+	}
+	return nil, err
+}
+
+func tryJournal() (io.Reader, error) {
+	r, err := sdjournal.NewJournalReader(sdjournal.JournalReaderConfig{
+		NumFromTail: uint64(0),
+		Matches: []sdjournal.Match{
+			{
+				Field: sdjournal.SD_JOURNAL_FIELD_TRANSPORT,
+				Value: "kernel",
+			},
+		},
+	})
+	if err != nil {
+		return nil, fmt.Errorf("Error opening journal: %v", err)
+	}
+	if r == nil {
+		return nil, fmt.Errorf("Got a nil reader")
+	}
+	glog.Info("Kernel log watcher use journal")
+	return r, nil
+}
+
+func tryLogFile(path string) (io.Reader, error) {
+	tail, err := tail.NewTail(path)
+	if err != nil {
+		return nil, err
+	}
+	glog.Infof("Kernel log watcher use log file: %s", path)
+	return tail, nil
+}
+
 func parseDuration(s string) (time.Duration, error) {
 	// If the duration is not configured, just return 0 by default
 	if s == "" {