Add first version of node-problem-detector

pkg/kernelmonitor/kernel_log_watcher.go

@@ -0,0 +1,166 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kernelmonitor
+
+import (
+	"bufio"
+	"os"
+
+	"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/golang/glog"
+	"github.com/hpcloud/tail"
+)
+
+const (
+	defaultKernelLogPath = "/var/log/kern.log"
+)
+
+// WatcherConfig is the configuration of kernel log watcher.
+type WatcherConfig struct {
+	KernelLogPath string `json:"logPath, omitempty"`
+}
+
+// KernelLogWatcher watches and translates the kernel log. Once there is new log line,
+// it will translate and report the log.
+type KernelLogWatcher interface {
+	// Watch starts the kernel log watcher and returns a watch channel.
+	Watch() (<-chan *types.KernelLog, error)
+	// Stop stops the kernel log watcher.
+	Stop()
+}
+
+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
+}
+
+// NewKernelLogWatcher creates a new kernel log watcher.
+func NewKernelLogWatcher(cfg WatcherConfig) KernelLogWatcher {
+	return &kernelLogWatcher{
+		trans: translator.NewDefaultTranslator(),
+		cfg:   cfg,
+		tomb:  util.NewTomb(),
+		// A capacity 1000 buffer should be enough
+		logCh: make(chan *types.KernelLog, 1000),
+	}
+}
+
+func (k *kernelLogWatcher) Watch() (<-chan *types.KernelLog, error) {
+	path := defaultKernelLogPath
+	if k.cfg.KernelLogPath != "" {
+		path = k.cfg.KernelLogPath
+	}
+	start, err := k.getStartPoint(path)
+	if err != nil {
+		return nil, err
+	}
+	// TODO(random-liu): If the file gets recreated during this interval, the logic
+	// will go wrong here.
+	// TODO(random-liu): Rate limit tail file.
+	// TODO(random-liu): Figure out what happens if log lines are removed.
+	k.tl, err = tail.TailFile(path, tail.Config{
+		Location: &tail.SeekInfo{
+			Offset: start,
+			Whence: os.SEEK_SET,
+		},
+		Poll:   true,
+		ReOpen: true,
+		Follow: true,
+	})
+	if err != nil {
+		return nil, err
+	}
+	glog.Info("Start watching kernel log")
+	go k.watchLoop()
+	return k.logCh, nil
+}
+
+func (k *kernelLogWatcher) Stop() {
+	k.tomb.Stop()
+}
+
+// watchLoop is the main watch loop of kernel log watcher.
+func (k *kernelLogWatcher) watchLoop() {
+	defer func() {
+		close(k.logCh)
+		k.tomb.Done()
+	}()
+	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)
+			if err != nil {
+				glog.Infof("Unable to parse line: %q, %v", line, err)
+				continue
+			}
+			k.logCh <- log
+		case <-k.tomb.Stopping():
+			k.tl.Stop()
+			glog.Infof("Stop watching kernel log")
+			return
+		}
+	}
+}
+
+// getStartPoint parses the newest kernel log file and try to find the latest reboot point.
+// Currently we rely on the kernel log timestamp to find the reboot point. The basic idea
+// is straight forward: In the whole lifecycle of a node, the kernel log timestamp should
+// always increase, only when it is reboot, the timestamp will decrease. We just parse the
+// log and find the latest timestamp decreasing, then it should be the latest reboot point.
+// TODO(random-liu): A drawback is that if the node is started long time ago, we'll only get
+// logs in the newest kernel log file. We may want to improve this in the future.
+func (k *kernelLogWatcher) getStartPoint(path string) (int64, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return -1, err
+	}
+	defer f.Close()
+	start := int64(0)
+	total := 0
+	lastTimestamp := int64(0)
+	reader := bufio.NewReader(f)
+	done := false
+	for !done {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			done = true
+		}
+		total += len(line)
+		log, err := k.trans.Translate(line)
+		if err != nil {
+			glog.Infof("unable to parse line: %q, %v", line, err)
+			continue
+		}
+		if log.Timestamp < lastTimestamp {
+			start = int64(total - len(line))
+		}
+		lastTimestamp = log.Timestamp
+	}
+	return start, nil
+}