Improve error handling

Author: mblaschke

errorhandling.go

@@ -7,9 +7,25 @@ import (
 )
 
 func buildErrorMessageForMetrics(err error, settings RequestMetricSettings) error {
-	settingLine := []string{
-		fmt.Sprintf("name[%v]", settings.Name),
-		fmt.Sprintf("filter[%v]", settings.Filter),
+	settingLine := []string{}
+
+	if settings.Name != "" {
+		settingLine = append(
+			settingLine,
+			fmt.Sprintf("name[%v]", settings.Name),
+		)
+	}
+
+	if settings.Filter != "" {
+		settingLine = append(
+			settingLine,
+			fmt.Sprintf("filter[%v]", settings.Filter),
+		)
 	}
-	return errors.New(fmt.Sprintf("%v: %v", strings.Join(settingLine, " "), err))
+
+	if len(settingLine) >= 1 {
+		err = errors.New(fmt.Sprintf("%v: %v", strings.Join(settingLine, " "), err))
+	}
+
+	return err
 }

probe_metrics_list.go

@@ -30,10 +30,8 @@ func probeMetricsListHandler(w http.ResponseWriter, r *http.Request) {
 	r = r.WithContext(ctx)
 
 	var settings RequestMetricSettings
-	if val, err := NewRequestMetricSettings(r); err == nil {
-		settings = val
-	} else {
-		Logger.Error(err)
+	if settings, err = NewRequestMetricSettings(r); err != nil {
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
@@ -50,8 +48,7 @@ func probeMetricsListHandler(w http.ResponseWriter, r *http.Request) {
 			list, err := azureInsightMetrics.ListResources(subscription, settings.Filter)
 
 			if err != nil {
-				err = buildErrorMessageForMetrics(err, settings)
-				Logger.Error(err)
+				Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 				http.Error(w, err.Error(), http.StatusBadRequest)
 				return
 			}
@@ -74,9 +71,8 @@ func probeMetricsListHandler(w http.ResponseWriter, r *http.Request) {
 							"result":         "success",
 						}).Inc()
 					} else {
-						err = buildErrorMessageForMetrics(err, settings)
 						Logger.Verbosef("name[%v]subscription[%v] failed fetching metrics for %v", settings.Name, subscription, *val.ID)
-						Logger.Warningln(err)
+						Logger.Warningln(buildErrorMessageForMetrics(err, settings))
 
 						prometheusMetricRequests.With(prometheus.Labels{
 							"subscriptionID": subscription,

probe_metrics_resource.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -29,25 +28,21 @@ func probeMetricsResourceHandler(w http.ResponseWriter, r *http.Request) {
 	r = r.WithContext(ctx)
 
 	var settings RequestMetricSettings
-	if val, err := NewRequestMetricSettings(r); err == nil {
-		settings = val
-	} else {
-		Logger.Error(err)
+	if settings, err = NewRequestMetricSettings(r); err != nil {
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
 
 	if len(settings.Subscriptions) != 1 {
-		err := errors.New("Invalid subscription, one subscription needs to be specified")
-		Logger.Error(err)
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
 	subscription := settings.Subscriptions[0]
 
 	if len(settings.Target) == 0 {
-		err := errors.New("Invalid target or target empty")
-		Logger.Error(err)
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
@@ -58,16 +53,15 @@ func probeMetricsResourceHandler(w http.ResponseWriter, r *http.Request) {
 		result, err := azureInsightMetrics.FetchMetrics(ctx, subscription, target, settings)
 
 		if err != nil {
-			err = buildErrorMessageForMetrics(err, settings)
-			Logger.Warningln(err)
+			Logger.Warningln(buildErrorMessageForMetrics(err, settings))
 			prometheusMetricRequests.With(prometheus.Labels{
 				"subscriptionID": subscription,
 				"handler":        PROBE_METRICS_RESOURCE_URL,
 				"filter":         "",
 				"result":         "error",
 			}).Inc()
 			http.Error(w, err.Error(), http.StatusBadRequest)
-			return
+			continue
 		}
 
 		Logger.Verbosef("subscription[%v] fetched metrics for %v", subscription, target)

probe_metrics_scrape.go

@@ -32,22 +32,20 @@ func probeMetricsScrapeHandler(w http.ResponseWriter, r *http.Request) {
 	r = r.WithContext(ctx)
 
 	var settings RequestMetricSettings
-	if val, err := NewRequestMetricSettings(r); err == nil {
-		settings = val
-	} else {
-		Logger.Error(err)
+	if settings, err = NewRequestMetricSettings(r); err != nil {
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
 	registry, metricGauge := azureInsightMetrics.CreatePrometheusRegistryAndMetricsGauge(settings.Name)
 
 	if metricTagName, err = paramsGetRequired(params, "metricTagName"); err != nil {
-		Logger.Error(err)
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
 	if aggregationTagName, err = paramsGetRequired(params, "aggregationTagName"); err != nil {
-		Logger.Error(err)
+		Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
@@ -61,7 +59,7 @@ func probeMetricsScrapeHandler(w http.ResponseWriter, r *http.Request) {
 			list, err := azureInsightMetrics.ListResources(subscription, settings.Filter)
 
 			if err != nil {
-				Logger.Error(err)
+				Logger.Errorln(buildErrorMessageForMetrics(err, settings))
 				http.Error(w, err.Error(), http.StatusBadRequest)
 				return
 			}
@@ -90,7 +88,7 @@ func probeMetricsScrapeHandler(w http.ResponseWriter, r *http.Request) {
 									"result":         "success",
 								}).Inc()
 							} else {
-								Logger.Warningln(err)
+								Logger.Warningln(buildErrorMessageForMetrics(err, settings))
 								prometheusMetricRequests.With(prometheus.Labels{
 									"subscriptionID": subscription,
 									"handler":        PROBE_METRICS_SCRAPE_URL,