Handle EPERM for syscall in timex collector

Handle case where Adjtimex syscall gets a permission denined error.

Fixes: https://github.com/prometheus/node_exporter/issues/1934

Signed-off-by: Ben Kochie <superq@gmail.com>

CHANGELOG.md

@@ -6,6 +6,7 @@
 * [ENHANCEMENT] Include TCP OutRsts in netstat metrics
 * [ENHANCEMENT] Added XFS inode operations to XFS metrics
 * [ENHANCEMENT] Remove CGO dependencies for OpenBSD amd64
+* [BUGFIX] Handle EPERM for syscall in timex collector
 * [BUGFIX]
 
 ## 1.0.1 / 2020-06-15

collector/timex.go

@@ -17,9 +17,12 @@
 package collector
 
 import (
+	"errors"
 	"fmt"
+	"os"
 
 	"github.com/go-kit/kit/log"
+	"github.com/go-kit/kit/log/level"
 	"github.com/prometheus/client_golang/prometheus"
 	"golang.org/x/sys/unix"
 )
@@ -163,6 +166,10 @@ func (c *timexCollector) Update(ch chan<- prometheus.Metric) error {
 
 	status, err := unix.Adjtimex(timex)
 	if err != nil {
+		if errors.Is(err, os.ErrPermission) {
+			level.Debug(c.logger).Log("msg", "Not collecting timex metrics", "err", err)
+			return ErrNoData
+		}
 		return fmt.Errorf("failed to retrieve adjtimex stats: %w", err)
 	}