prom-oops-exporter.go

package main

import (
	"bufio"
	"context"
	"io"
	"log"
	"net/http"
	"os"
	"regexp"
	"syscall"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	oopsCounter = prometheus.NewCounterVec(prometheus.CounterOpts{
		Name: "kernel_oops_total",
		Help: "Total number of kernel oops",
	},
		// XXX: kernel/sys metadata can probably be grouped lefted with kube_node_info or node exporter
		// metrics, but here we go..
		[]string{"kernel_version", "kernel_release"},
	)

	oopsPattern   = regexp.MustCompile(`kernel: \[.*\] Oops: \d+`)
	kernelVersion string
	kernelRelease string
)

func init() {
	prometheus.MustRegister(oopsCounter)
}

func initInventory() error {
	var (
		uname     syscall.Utsname
		int8ToStr = func(arr []int8) string {
			b := make([]byte, 0, len(arr))
			for _, c := range arr {
				if c == 0 {
					break
				}
				b = append(b, byte(c))
			}
			return string(b)
		}
	)

	if err := syscall.Uname(&uname); err != nil {
		return err
	}
	kernelRelease = int8ToStr(uname.Release[:])
	kernelVersion = int8ToStr(uname.Version[:])

	log.Printf("kernel release: %s, kernel version: %s\n", kernelRelease, kernelVersion)
	return nil
}

func oopsWatch(ctx context.Context) error {
	f, err := os.Open("/var/log/kern.log")
	if err != nil {
		return err
	}
	defer f.Close()

	f.Seek(0, 2)

	r := bufio.NewReader(f)

	for {
		select {
		case <-ctx.Done():
			return nil
		default:
			line, err := r.ReadString('\n')
			if err != nil {
				if err == io.EOF {
					<-time.After(1 * time.Second)
					continue
				}
			}

			if oopsPattern.MatchString(line) {
				oopsCounter.With(prometheus.Labels{
					"kernel_version": kernelVersion,
					"kernel_release": kernelRelease,
				}).Inc()
			}
		}
	}
}

func main() {
	ctx := context.Background()
	if err := initInventory(); err != nil {
		log.Fatal(err)
	}

	go func() {
		if err := oopsWatch(ctx); err != nil {
			log.Fatal(err)
		}
	}()

	http.Handle("/metrics", promhttp.Handler())
	log.Fatal(http.ListenAndServe(":8080", nil))
}