Add metric for refresh duration

internal/collector/collector.go

@@ -20,6 +20,10 @@ var (
 		refreshPrefix+"_time",
 		"Contains the time of the last refresh try, successful or not.",
 		nil, nil)
+	refreshDurationDesc = prometheus.NewDesc(
+		refreshPrefix+"_duration_seconds",
+		"Contains the time it took for the last refresh to complete, even if it was unsuccessful.",
+		nil, nil)
 
 	cacheTimestampDesc = prometheus.NewDesc(
 		prefix+"cache_updated_time",
@@ -111,6 +115,7 @@ type NetatmoCollector struct {
 	Client              *netatmo.Client
 	lastRefresh         time.Time
 	lastRefreshError    error
+	lastRefreshDuration time.Duration
 	cacheLock           sync.RWMutex
 	cacheTimestamp      time.Time
 	cachedData          *netatmo.DeviceCollection
@@ -135,6 +140,7 @@ func (c *NetatmoCollector) Collect(mChan chan<- prometheus.Metric) {
 	}
 	c.sendMetric(mChan, netatmoUpDesc, prometheus.GaugeValue, upValue)
 	c.sendMetric(mChan, refreshTimestampDesc, prometheus.GaugeValue, convertTime(c.lastRefresh))
+	c.sendMetric(mChan, refreshDurationDesc, prometheus.GaugeValue, c.lastRefreshDuration.Seconds())
 
 	c.cacheLock.RLock()
 	defer c.cacheLock.RUnlock()
@@ -156,6 +162,10 @@ func (c *NetatmoCollector) refreshData(now time.Time) {
 	c.Log.Debugf("Refresh interval elapsed: %s > %s", now.Sub(c.lastRefresh), c.RefreshInterval)
 	c.lastRefresh = now
 
+	defer func(start time.Time) {
+		c.lastRefreshDuration = time.Since(start)
+	}(time.Now())
+
 	devices, err := c.Client.Read()
 	if err != nil {
 		c.Log.Errorf("Error during refresh: %s", err)