Make wifi collector fail gracefully if metrics not available

1 files changed, 19 insertions, 11 deletions

diff --git a/collector/wifi_linux.go b/collector/wifi_linux.go
index 4eb1b68..994f808 100644
--- a/collector/wifi_linux.go
+++ b/collector/wifi_linux.go
@@ -18,10 +18,12 @@ import (
         "flag"
         "fmt"
         "io/ioutil"
+        "os"
         "path/filepath"
 
         "github.com/mdlayher/wifi"
         "github.com/prometheus/client_golang/prometheus"
+        "github.com/prometheus/common/log"
 )
 
 type wifiCollector struct {
@@ -35,8 +37,6 @@ type wifiCollector struct {
         StationTransmitRetriesTotal  *prometheus.Desc
         StationTransmitFailedTotal   *prometheus.Desc
         StationBeaconLossTotal       *prometheus.Desc
-
-        stat wifiStater
 }
 
 var (
@@ -51,16 +51,12 @@ var _ wifiStater = &wifi.Client{}
 
 // wifiStater is an interface used to swap out a *wifi.Client for end to end tests.
 type wifiStater interface {
+        Close() error
         Interfaces() ([]*wifi.Interface, error)
         StationInfo(ifi *wifi.Interface) (*wifi.StationInfo, error)
 }
 
 func NewWifiCollector() (Collector, error) {
-        stat, err := newWifiStater(*collectorWifi)
-        if err != nil {
-                return nil, fmt.Errorf("failed to access wifi data: %v", err)
-        }
-
         const (
                 subsystem = "wifi"
         )
@@ -132,13 +128,23 @@ func NewWifiCollector() (Collector, error) {
                         labels,
                         nil,
                 ),
-
-                stat: stat,
         }, nil
 }
 
 func (c *wifiCollector) Update(ch chan<- prometheus.Metric) error {
-        ifis, err := c.stat.Interfaces()
+        stat, err := newWifiStater(*collectorWifi)
+        if err != nil {
+                // Cannot access wifi metrics, report no error
+                if os.IsNotExist(err) {
+                        log.Debug("wifi collector metrics are not available for this system")
+                        return nil
+                }
+
+                return fmt.Errorf("failed to access wifi data: %v", err)
+        }
+        defer stat.Close()
+
+        ifis, err := stat.Interfaces()
         if err != nil {
                 return fmt.Errorf("failed to retrieve wifi interfaces: %v", err)
         }
@@ -149,7 +155,7 @@ func (c *wifiCollector) Update(ch chan<- prometheus.Metric) error {
                         continue
                 }
 
-                info, err := c.stat.StationInfo(ifi)
+                info, err := stat.StationInfo(ifi)
                 if err != nil {
                         return fmt.Errorf("failed to retrieve station info for device %s: %v",
                                 ifi.Name, err)
@@ -260,6 +266,8 @@ func (s *mockWifiStater) unmarshalJSONFile(filename string, v interface{}) error
         return json.Unmarshal(b, v)
 }
 
+func (s *mockWifiStater) Close() error { return nil }
+
 func (s *mockWifiStater) Interfaces() ([]*wifi.Interface, error) {
         var ifis []*wifi.Interface
         if err := s.unmarshalJSONFile("interfaces.json", &ifis); err != nil {