fix: separate nginx_up availability from scrape success #978

collector/helper.go

@@ -1,6 +1,8 @@
 package collector
 
 import (
+	"strings"
+
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -22,6 +24,33 @@ func newUpMetric(namespace string, constLabels map[string]string) prometheus.Gau
 	})
 }
 
+func newScrapeSuccessMetric(namespace string, constLabels map[string]string) prometheus.Gauge {
+	return prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace:   namespace,
+		Name:        "scrape_success",
+		Help:        "Whether the last scrape of NGINX metrics was successful",
+		ConstLabels: constLabels,
+	})
+}
+
+func newScrapeDurationMetric(namespace string, constLabels map[string]string) prometheus.Gauge {
+	return prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace:   namespace,
+		Name:        "scrape_duration_seconds",
+		Help:        "Duration of the last scrape in seconds",
+		ConstLabels: constLabels,
+	})
+}
+
+func newScrapeErrorsTotalMetric(namespace string, constLabels map[string]string) *prometheus.CounterVec {
+	return prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace:   namespace,
+		Name:        "scrape_errors_total",
+		Help:        "Total number of scrape errors by type",
+		ConstLabels: constLabels,
+	}, []string{"type"})
+}
+
 // MergeLabels merges two maps of labels.
 func MergeLabels(a map[string]string, b map[string]string) map[string]string {
 	c := make(map[string]string)
@@ -35,3 +64,14 @@ func MergeLabels(a map[string]string, b map[string]string) map[string]string {
 
 	return c
 }
+
+func isNetworkError(errorMsg string) bool {
+	return strings.Contains(errorMsg, "failed to get") ||
+		strings.Contains(errorMsg, "connection") ||
+		strings.Contains(errorMsg, "timeout") ||
+		strings.Contains(errorMsg, "refused")
+}
+
+func isHTTPError(errorMsg string) bool {
+	return strings.Contains(errorMsg, "expected 200 response")
+}

collector/nginx.go

@@ -3,18 +3,22 @@ package collector
 import (
 	"log/slog"
 	"sync"
+	"time"
 
 	"github.com/nginx/nginx-prometheus-exporter/client"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
 // NginxCollector collects NGINX metrics. It implements prometheus.Collector interface.
 type NginxCollector struct {
-	upMetric    prometheus.Gauge
-	logger      *slog.Logger
-	nginxClient *client.NginxClient
-	metrics     map[string]*prometheus.Desc
-	mutex       sync.Mutex
+	upMetric             prometheus.Gauge
+	scrapeSuccessMetric  prometheus.Gauge
+	scrapeDurationMetric prometheus.Gauge
+	scrapeErrorsTotal    *prometheus.CounterVec
+	logger               *slog.Logger
+	nginxClient          *client.NginxClient
+	metrics              map[string]*prometheus.Desc
+	mutex                sync.Mutex
 }
 
 // NewNginxCollector creates an NginxCollector.
@@ -31,14 +35,20 @@ func NewNginxCollector(nginxClient *client.NginxClient, namespace string, constL
 			"connections_waiting":  newGlobalMetric(namespace, "connections_waiting", "Idle client connections", constLabels),
 			"http_requests_total":  newGlobalMetric(namespace, "http_requests_total", "Total http requests", constLabels),
 		},
-		upMetric: newUpMetric(namespace, constLabels),
+		upMetric:             newUpMetric(namespace, constLabels),
+		scrapeSuccessMetric:  newScrapeSuccessMetric(namespace, constLabels),
+		scrapeDurationMetric: newScrapeDurationMetric(namespace, constLabels),
+		scrapeErrorsTotal:    newScrapeErrorsTotalMetric(namespace, constLabels),
 	}
 }
 
 // Describe sends the super-set of all possible descriptors of NGINX metrics
 // to the provided channel.
 func (c *NginxCollector) Describe(ch chan<- *prometheus.Desc) {
 	ch <- c.upMetric.Desc()
+	ch <- c.scrapeSuccessMetric.Desc()
+	ch <- c.scrapeDurationMetric.Desc()
+	c.scrapeErrorsTotal.Describe(ch)
 
 	for _, m := range c.metrics {
 		ch <- m
@@ -50,16 +60,53 @@ func (c *NginxCollector) Collect(ch chan<- prometheus.Metric) {
 	c.mutex.Lock() // To protect metrics from concurrent collects
 	defer c.mutex.Unlock()
 
+	start := time.Now()
 	stats, err := c.nginxClient.GetStubStats()
+	duration := time.Since(start).Seconds()
+	c.scrapeDurationMetric.Set(duration)
+	ch <- c.scrapeDurationMetric
+
 	if err != nil {
-		c.upMetric.Set(nginxDown)
-		ch <- c.upMetric
-		c.logger.Error("error getting stats", "error", err.Error())
+		c.handleScrapeError(ch, err)
 		return
 	}
 
+	c.handleScrapeSuccess(ch, stats)
+}
+
+func (c *NginxCollector) handleScrapeError(ch chan<- prometheus.Metric, err error) {
+	errorMsg := err.Error()
+	var errorType string
+
+	switch {
+	case isNetworkError(errorMsg):
+		c.upMetric.Set(nginxDown)
+		errorType = "network"
+	case isHTTPError(errorMsg):
+		c.upMetric.Set(nginxUp)
+		errorType = "http"
+	default:
+		c.upMetric.Set(nginxUp)
+		errorType = "parse"
+	}
+
+	c.scrapeErrorsTotal.WithLabelValues(errorType).Inc()
+	c.scrapeSuccessMetric.Set(0)
+
+	ch <- c.upMetric
+	ch <- c.scrapeSuccessMetric
+	c.scrapeErrorsTotal.Collect(ch)
+
+	c.logger.Error("error getting stats", "error", err.Error(), "type", errorType)
+}
+
+func (c *NginxCollector) handleScrapeSuccess(ch chan<- prometheus.Metric, stats *client.StubStats) {
 	c.upMetric.Set(nginxUp)
+	c.scrapeSuccessMetric.Set(1)
+
 	ch <- c.upMetric
+	ch <- c.scrapeSuccessMetric
+	c.scrapeErrorsTotal.Collect(ch)
 
 	ch <- prometheus.MustNewConstMetric(c.metrics["connections_active"],
 		prometheus.GaugeValue, float64(stats.Connections.Active))

collector/nginx_test.go

@@ -0,0 +1,142 @@
+package collector
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestIsNetworkError(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		errorMsg string
+		want     bool
+	}{
+		{
+			name:     "network connection error",
+			errorMsg: "failed to get http://localhost:8080/stub_status: connection refused",
+			want:     true,
+		},
+		{
+			name:     "network timeout error",
+			errorMsg: "failed to get http://localhost:8080/stub_status: timeout",
+			want:     true,
+		},
+		{
+			name:     "HTTP error",
+			errorMsg: "expected 200 response, got 404",
+			want:     false,
+		},
+		{
+			name:     "parse error",
+			errorMsg: "failed to parse response body",
+			want:     false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := isNetworkError(tt.errorMsg); got != tt.want {
+				t.Errorf("isNetworkError() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsHTTPError(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		errorMsg string
+		want     bool
+	}{
+		{
+			name:     "HTTP 404 error",
+			errorMsg: "expected 200 response, got 404",
+			want:     true,
+		},
+		{
+			name:     "HTTP 500 error",
+			errorMsg: "expected 200 response, got 500",
+			want:     true,
+		},
+		{
+			name:     "network error",
+			errorMsg: "failed to get http://localhost:8080/stub_status: connection refused",
+			want:     false,
+		},
+		{
+			name:     "parse error",
+			errorMsg: "failed to parse response body",
+			want:     false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := isHTTPError(tt.errorMsg); got != tt.want {
+				t.Errorf("isHTTPError() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestNewScrapeSuccessMetric(t *testing.T) {
+	t.Parallel()
+
+	metric := newScrapeSuccessMetric("nginx", map[string]string{"job": "nginx"})
+
+	if metric == nil {
+		t.Error("newScrapeSuccessMetric() returned nil")
+	}
+
+	desc := metric.Desc().String()
+	if !strings.Contains(desc, "nginx_scrape_success") {
+		t.Errorf("metric description should contain 'nginx_scrape_success', got: %s", desc)
+	}
+}
+
+func TestNewScrapeDurationMetric(t *testing.T) {
+	t.Parallel()
+
+	metric := newScrapeDurationMetric("nginx", map[string]string{"job": "nginx"})
+
+	if metric == nil {
+		t.Error("newScrapeDurationMetric() returned nil")
+	}
+
+	desc := metric.Desc().String()
+	if !strings.Contains(desc, "nginx_scrape_duration_seconds") {
+		t.Errorf("metric description should contain 'nginx_scrape_duration_seconds', got: %s", desc)
+	}
+}
+
+func TestNewScrapeErrorsTotalMetric(t *testing.T) {
+	t.Parallel()
+
+	metric := newScrapeErrorsTotalMetric("nginx", map[string]string{"job": "nginx"})
+
+	if metric == nil {
+		t.Error("newScrapeErrorsTotalMetric() returned nil")
+		return
+	}
+
+	ch := make(chan *prometheus.Desc, 10)
+	metric.Describe(ch)
+	close(ch)
+
+	count := 0
+	for range ch {
+		count++
+	}
+
+	if count == 0 {
+		t.Error("metric should have descriptions")
+	}
+}