Fix for iamseth/oracledb_exporter#459

collector/collector.go

@@ -238,9 +238,11 @@
 	wg.Wait()
 }
 
 func (e *Exporter) scrape(ch chan<- prometheus.Metric) {
 	e.totalScrapes.Inc()
 	var err error
+	var errmutex sync.Mutex
+
 	defer func(begun time.Time) {
 		e.duration.Set(time.Since(begun).Seconds())
 		if err == nil {
@@ -277,7 +279,7 @@
 
 	for _, metric := range e.metricsToScrape.Metric {
 		wg.Add(1)
 		metric := metric //https://golang.org/doc/faq#closures_and_goroutines
 
 		f := func() {
 			defer wg.Done()
@@ -303,7 +305,7 @@
 			}
 
 			for column, metricType := range metric.MetricsType {
 				if metricType == "histogram" {
 					_, ok := metric.MetricsBuckets[column]
 					if !ok {
 						level.Error(e.logger).Log("Unable to find MetricsBuckets configuration key for metric. (metric=" + column + ")")
@@ -313,8 +315,13 @@
 			}
 
 			scrapeStart := time.Now()
-			if err = e.ScrapeMetric(e.db, ch, metric); err != nil {
-				level.Error(e.logger).Log("scrapeMetricContext", metric.Context, "ScrapeDuration", time.Since(scrapeStart), "msg", err.Error())
+			if err1 := e.ScrapeMetric(e.db, ch, metric); err1 != nil {
+				errmutex.Lock()
+				{
+					err = err1
+				}
+				errmutex.Unlock()
+				level.Error(e.logger).Log("scrapeMetricContext", metric.Context, "ScrapeDuration", time.Since(scrapeStart), "msg", err1.Error())
 				e.scrapeErrors.WithLabelValues(metric.Context).Inc()
 			} else {
 				level.Debug(e.logger).Log("successfully scraped metric: ", metric.Context, metric.MetricsDesc, time.Since(scrapeStart))
@@ -436,8 +443,8 @@
 }
 
 // generic method for retrieving metrics.
 func (e *Exporter) scrapeGenericValues(db *sql.DB, ch chan<- prometheus.Metric, context string, labels []string,
 	metricsDesc map[string]string, metricsType map[string]string, metricsBuckets map[string]map[string]string, fieldToAppend string, ignoreZeroResult bool, request string) error {
 	metricsCount := 0
 	genericParser := func(row map[string]string) error {
 		// Construct labels value