From dc9eb0230168f93fd35e0463b544c0feb33ef364 Mon Sep 17 00:00:00 2001
From: Pascal Zimmermann <pascal.zimmermann01@sap.com>
Date: Mon, 30 Jan 2023 15:52:54 +0100
Subject: [PATCH] fix(inputs.prometheus): Set the timeout for slow running API
 endpoints correctly (#12559)

---
 plugins/inputs/prometheus/prometheus.go      |  1 +
 plugins/inputs/prometheus/prometheus_test.go | 59 ++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/plugins/inputs/prometheus/prometheus.go b/plugins/inputs/prometheus/prometheus.go
index 6c8cd34be..edf35bcae 100644
--- a/plugins/inputs/prometheus/prometheus.go
+++ b/plugins/inputs/prometheus/prometheus.go
@@ -163,6 +163,7 @@ func (p *Prometheus) Init() error {
 	}
 
 	ctx := context.Background()
+	p.HTTPClientConfig.Timeout = p.ResponseTimeout
 	client, err := p.HTTPClientConfig.CreateClient(ctx, p.Log)
 	if err != nil {
 		return err
diff --git a/plugins/inputs/prometheus/prometheus_test.go b/plugins/inputs/prometheus/prometheus_test.go
index d89f94ec0..caa75ba38 100644
--- a/plugins/inputs/prometheus/prometheus_test.go
+++ b/plugins/inputs/prometheus/prometheus_test.go
@@ -1,7 +1,9 @@
 package prometheus
 
 import (
+	"errors"
 	"fmt"
+	"github.com/influxdata/telegraf/config"
 	"math"
 	"net/http"
 	"net/http/httptest"
@@ -137,6 +139,63 @@ func TestPrometheusGeneratesMetricsAlthoughFirstDNSFailsIntegration(t *testing.T
 	require.True(t, acc.HasTimestamp("test_metric", time.Unix(1490802350, 0)))
 }
 
+func TestPrometheusGeneratesMetricsSlowEndpoint(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(4 * time.Second)
+		_, err := fmt.Fprintln(w, sampleTextFormat)
+		require.NoError(t, err)
+	}))
+	defer ts.Close()
+
+	p := &Prometheus{
+		Log:             testutil.Logger{},
+		URLs:            []string{ts.URL},
+		URLTag:          "url",
+		ResponseTimeout: config.Duration(time.Second * 5),
+	}
+	err := p.Init()
+	require.NoError(t, err)
+
+	var acc testutil.Accumulator
+
+	err = acc.GatherError(p.Gather)
+	require.NoError(t, err)
+
+	require.True(t, acc.HasFloatField("go_gc_duration_seconds", "count"))
+	require.True(t, acc.HasFloatField("go_goroutines", "gauge"))
+	require.True(t, acc.HasFloatField("test_metric", "value"))
+	require.True(t, acc.HasTimestamp("test_metric", time.Unix(1490802350, 0)))
+	require.False(t, acc.HasTag("test_metric", "address"))
+	require.True(t, acc.TagValue("test_metric", "url") == ts.URL+"/metrics")
+}
+
+func TestPrometheusGeneratesMetricsSlowEndpointHitTheTimeout(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(6 * time.Second)
+		_, err := fmt.Fprintln(w, sampleTextFormat)
+		require.NoError(t, err)
+	}))
+	defer ts.Close()
+
+	p := &Prometheus{
+		Log:             testutil.Logger{},
+		URLs:            []string{ts.URL},
+		URLTag:          "url",
+		ResponseTimeout: config.Duration(time.Second * 5),
+	}
+	err := p.Init()
+	require.NoError(t, err)
+
+	var acc testutil.Accumulator
+
+	err = acc.GatherError(p.Gather)
+	errMessage := fmt.Sprintf("error making HTTP request to %s/metrics: Get \"%s/metrics\": "+
+		"context deadline exceeded (Client.Timeout exceeded while awaiting headers)", ts.URL, ts.URL)
+	errExpected := errors.New(errMessage)
+	require.Equal(t, errExpected, err)
+	require.Error(t, err)
+}
+
 func TestPrometheusGeneratesSummaryMetricsV2(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_, err := fmt.Fprintln(w, sampleSummaryTextFormat)