lib/promscrape: fixed reload on max_scrape_size change (#7282)

### Describe Your Changes

fixed reload on max_scrape_size change
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7260

### Checklist

The following checks are **mandatory**:

- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).

---------

Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>

docs/changelog/CHANGELOG.md

@@ -35,6 +35,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * BUGFIX: [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): properly apply replication factor when storage node groups are used and replication factor is configured via global value such as `-replicationFactor=2`. Previously, global replication factor was ignored for storage node groups. See [these docs](https://docs.victoriametrics.com/cluster-victoriametrics/#vmstorage-groups-at-vmselect) for more information about storage groups configuration.
 * BUGFIX: `vmselect` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): properly process response in [multi-level cluster setup](https://docs.victoriametrics.com/cluster-victoriametrics/#multi-level-cluster-setup). Before, vmselect could return no data in multi-level setup. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7270) for details. The issue was introduced in [v1.104.0](https://docs.victoriametrics.com/changelog/#v11040).
 * BUGFIX: [vmalert](https://docs.victoriametrics.com/vmalert): properly apply configuration changes during hot-reload to rule groups that haven't started yet. Previously, configuration updates to such groups could have resulted into blocking all evaluations within the group, until vmalert restart.
+* BUGFIX: [Single-node VictoriaMetrics](https://docs.victoriametrics.com/)  and [vmagent](https://docs.victoriametrics.com/vmagent/): properly update `max_scrape_size` param change during [hot-reload](https://docs.victoriametrics.com/vmagent/#configuration-update). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7260).
 
 ## [v1.104.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.104.0)
 

lib/promscrape/client.go

@@ -171,7 +171,7 @@ func (c *client) ReadData(dst *bytesutil.ByteBuffer) error {
 		maxScrapeSizeExceeded.Inc()
 		return fmt.Errorf("the response from %q exceeds -promscrape.maxScrapeSize or max_scrape_size in the scrape config (%d bytes). "+
 			"Possible solutions are: reduce the response size for the target, increase -promscrape.maxScrapeSize command-line flag, "+
-			"increase max_scrape_size value in scrape config for the given target", c.scrapeURL, maxScrapeSize.N)
+			"increase max_scrape_size value in scrape config for the given target", c.scrapeURL, c.maxScrapeSize)
 	}
 	return nil
 }

lib/promscrape/scraper_test.go

@@ -0,0 +1,81 @@
+package promscrape
+
+import (
+	"fmt"
+	"math/rand"
+	"testing"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/auth"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/prompbmarshal"
+)
+
+func TestScraperReload(t *testing.T) {
+	f := func(oldCfgData, newCfgData string, reloadExpected bool) {
+		pushData := func(_ *auth.Token, _ *prompbmarshal.WriteRequest) {}
+		globalStopChan = make(chan struct{})
+		defer close(globalStopChan)
+
+		randName := rand.Int()
+		sg := newScraperGroup(fmt.Sprintf("static_configs_%d", randName), pushData, globalStopChan)
+		defer sg.stop()
+
+		scrapeConfigPath := "test-scrape.yaml"
+		var oldCfg, newCfg Config
+		if err := oldCfg.parseData([]byte(oldCfgData), scrapeConfigPath); err != nil {
+			t.Fatalf("cannot create old config: %s", err)
+		}
+		oldSws := oldCfg.getStaticScrapeWork()
+		sg.update(oldSws)
+		oldChangesCount := sg.changesCount.Get()
+
+		if err := newCfg.parseData([]byte(newCfgData), scrapeConfigPath); err != nil {
+			t.Fatalf("cannot create new config: %s", err)
+		}
+		doReload := (&newCfg).mustRestart(&oldCfg)
+		if doReload != reloadExpected {
+			t.Errorf("unexpected reload behaviour:\nexpected: %t\nactual: %t\n", reloadExpected, doReload)
+		}
+		newSws := newCfg.getStaticScrapeWork()
+		sg.update(newSws)
+		newChangesCount := sg.changesCount.Get()
+		if (newChangesCount != oldChangesCount) != reloadExpected {
+			t.Errorf("expected reload behaviour:\nexpected reload happen: %t\nactual reload happen: %t", reloadExpected, newChangesCount != oldChangesCount)
+		}
+	}
+	f(`
+scrape_configs:
+- job_name: node-exporter
+  static_configs:
+    - targets:
+        - localhost:8429`, `
+scrape_configs:
+- job_name: node-exporter
+  static_configs:
+    - targets:
+        - localhost:8429`, false)
+	f(`
+scrape_configs:
+- job_name: node-exporter
+  static_configs:
+    - targets:
+        - localhost:8429`, `
+scrape_configs:
+- job_name: node-exporter
+  static_configs:
+    - targets:
+        - localhost:8429
+        - localhost:8428`, true)
+	f(`
+scrape_configs:
+- job_name: node-exporter
+  max_scrape_size: 1KiB
+  static_configs:
+    - targets:
+        - localhost:8429`, `
+scrape_configs:
+- job_name: node-exporter
+  max_scrape_size: 2KiB
+  static_configs:
+    - targets:
+        - localhost:8429`, true)
+}

lib/promscrape/scrapework.go

@@ -163,13 +163,13 @@ func (sw *ScrapeWork) key() string {
 	// Do not take into account OriginalLabels, since they can be changed with relabeling.
 	// Do not take into account RelabelConfigs, since it is already applied to Labels.
 	// Take into account JobNameOriginal in order to capture the case when the original job_name is changed via relabeling.
-	key := fmt.Sprintf("JobNameOriginal=%s, ScrapeURL=%s, ScrapeInterval=%s, ScrapeTimeout=%s, HonorLabels=%v, HonorTimestamps=%v, DenyRedirects=%v, Labels=%s, "+
+	key := fmt.Sprintf("JobNameOriginal=%s, ScrapeURL=%s, ScrapeInterval=%s, ScrapeTimeout=%s, HonorLabels=%v, "+
-		"ExternalLabels=%s, "+
+		"HonorTimestamps=%v, DenyRedirects=%v, Labels=%s, ExternalLabels=%s, MaxScrapeSize=%d, "+
 		"ProxyURL=%s, ProxyAuthConfig=%s, AuthConfig=%s, MetricRelabelConfigs=%q, "+
 		"SampleLimit=%d, DisableCompression=%v, DisableKeepAlive=%v, StreamParse=%v, "+
 		"ScrapeAlignInterval=%s, ScrapeOffset=%s, SeriesLimit=%d, NoStaleMarkers=%v",
-		sw.jobNameOriginal, sw.ScrapeURL, sw.ScrapeInterval, sw.ScrapeTimeout, sw.HonorLabels, sw.HonorTimestamps, sw.DenyRedirects, sw.Labels.String(),
+		sw.jobNameOriginal, sw.ScrapeURL, sw.ScrapeInterval, sw.ScrapeTimeout, sw.HonorLabels,
-		sw.ExternalLabels.String(),
+		sw.HonorTimestamps, sw.DenyRedirects, sw.Labels.String(), sw.ExternalLabels.String(), sw.MaxScrapeSize,
 		sw.ProxyURL.String(), sw.ProxyAuthConfig.String(), sw.AuthConfig.String(), sw.MetricRelabelConfigs.String(),
 		sw.SampleLimit, sw.DisableCompression, sw.DisableKeepAlive, sw.StreamParse,
 		sw.ScrapeAlignInterval, sw.ScrapeOffset, sw.SeriesLimit, sw.NoStaleMarkers)