Keep relabeled scrape interval and timeout on reloads (#10916)

* Preserve relabeled scrape interval and timeout on reloads

Signed-off-by: Xiaonan Shen <s@sxn.dev>

scrape/manager_test.go

@@ -406,7 +406,9 @@ scrape_configs:
 	}
 	sp := &scrapePool{
 		appendable: &nopAppendable{},
-		activeTargets: map[uint64]*Target{},
+		activeTargets: map[uint64]*Target{
+			1: {},
+		},
 		loops: map[uint64]loop{
 			1: noopLoop(),
 		},

scrape/scrape.go

@@ -426,8 +426,9 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 			cache = newScrapeCache()
 		}
 
+		t := sp.activeTargets[fp]
+		interval, timeout, err := t.intervalAndTimeout(interval, timeout)
 		var (
-			t       = sp.activeTargets[fp]
 			s       = &targetScraper{Target: t, client: sp.client, timeout: timeout, bodySizeLimit: bodySizeLimit}
 			newLoop = sp.newLoop(scrapeLoopOptions{
 				target:          t,
@@ -442,6 +443,9 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 				timeout:         timeout,
 			})
 		)
+		if err != nil {
+			newLoop.setForcedError(err)
+		}
 		wg.Add(1)
 
 		go func(oldLoop, newLoop loop) {

scrape/scrape_test.go

@@ -325,6 +325,40 @@ func TestScrapePoolReload(t *testing.T) {
 	require.Equal(t, numTargets, len(sp.loops), "Unexpected number of stopped loops after reload")
 }
 
+func TestScrapePoolReloadPreserveRelabeledIntervalTimeout(t *testing.T) {
+	reloadCfg := &config.ScrapeConfig{
+		ScrapeInterval: model.Duration(3 * time.Second),
+		ScrapeTimeout:  model.Duration(2 * time.Second),
+	}
+	newLoop := func(opts scrapeLoopOptions) loop {
+		l := &testLoop{interval: time.Duration(opts.interval), timeout: time.Duration(opts.timeout)}
+		l.startFunc = func(interval, timeout time.Duration, errc chan<- error) {
+			require.Equal(t, 5*time.Second, interval, "Unexpected scrape interval")
+			require.Equal(t, 3*time.Second, timeout, "Unexpected scrape timeout")
+		}
+		return l
+	}
+	sp := &scrapePool{
+		appendable: &nopAppendable{},
+		activeTargets: map[uint64]*Target{
+			1: {
+				labels: labels.FromStrings(model.ScrapeIntervalLabel, "5s", model.ScrapeTimeoutLabel, "3s"),
+			},
+		},
+		loops: map[uint64]loop{
+			1: noopLoop(),
+		},
+		newLoop: newLoop,
+		logger:  nil,
+		client:  http.DefaultClient,
+	}
+
+	err := sp.reload(reloadCfg)
+	if err != nil {
+		t.Fatalf("unable to reload configuration: %s", err)
+	}
+}
+
 func TestScrapePoolTargetLimit(t *testing.T) {
 	var wg sync.WaitGroup
 	// On starting to run, new loops created on reload check whether their preceding