lib/promscrape: add ability to set disable_compression and disable_keepalive options in scrape_config section of the config passed to -promscrape.config

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/580

app/vmagent/README.md

@@ -147,14 +147,20 @@ The following scrape types in [scrape_config](https://prometheus.io/docs/prometh
 * `dns_sd_configs` - for scraping targets discovered from DNS records (SRV, A and AAAA).
   See [dns_sd_config](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#dns_sd_config) for details.
 
+File feature requests at [our issue tracker](https://github.com/VictoriaMetrics/VictoriaMetrics/issues) if you need other service discovery mechanisms to be supported by `vmagent`.
+
+`vmagent` also support the following additional options in `scrape_config` section:
+
+* `disable_compression: true` - for disabling response compression on a per-job basis. By default `vmagent` requests compressed responses from scrape targets
+  in order to save network bandwidth.
+* `disable_keepalive: true` - for disabling [HTTP keep-alive connections](https://en.wikipedia.org/wiki/HTTP_persistent_connection) on a per-job basis.
+  By default `vmagent` uses keep-alive connections to scrape targets in order to reduce overhead on connection re-establishing.
+
 Note that `vmagent` doesn't support `refresh_interval` option these scrape configs. Use the corresponding `-promscrape.*CheckInterval`
 command-line flag instead. For example, `-promscrape.consulSDCheckInterval=60s` sets `refresh_interval` for all the `consul_sd_configs`
 entries to 60s. Run `vmagent -help` in order to see default values for `-promscrape.*CheckInterval` flags.
 
 
-File feature requests at [our issue tracker](https://github.com/VictoriaMetrics/VictoriaMetrics/issues) if you need other service discovery mechanisms to be supported by `vmagent`.
-
-
 ### Adding labels to metrics
 
 Labels can be added to metrics via the following mechanisms:

docs/vmagent.md

@@ -147,14 +147,20 @@ The following scrape types in [scrape_config](https://prometheus.io/docs/prometh
 * `dns_sd_configs` - for scraping targets discovered from DNS records (SRV, A and AAAA).
   See [dns_sd_config](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#dns_sd_config) for details.
 
+File feature requests at [our issue tracker](https://github.com/VictoriaMetrics/VictoriaMetrics/issues) if you need other service discovery mechanisms to be supported by `vmagent`.
+
+`vmagent` also support the following additional options in `scrape_config` section:
+
+* `disable_compression: true` - for disabling response compression on a per-job basis. By default `vmagent` requests compressed responses from scrape targets
+  in order to save network bandwidth.
+* `disable_keepalive: true` - for disabling [HTTP keep-alive connections](https://en.wikipedia.org/wiki/HTTP_persistent_connection) on a per-job basis.
+  By default `vmagent` uses keep-alive connections to scrape targets in order to reduce overhead on connection re-establishing.
+
 Note that `vmagent` doesn't support `refresh_interval` option these scrape configs. Use the corresponding `-promscrape.*CheckInterval`
 command-line flag instead. For example, `-promscrape.consulSDCheckInterval=60s` sets `refresh_interval` for all the `consul_sd_configs`
 entries to 60s. Run `vmagent -help` in order to see default values for `-promscrape.*CheckInterval` flags.
 
 
-File feature requests at [our issue tracker](https://github.com/VictoriaMetrics/VictoriaMetrics/issues) if you need other service discovery mechanisms to be supported by `vmagent`.
-
-
 ### Adding labels to metrics
 
 Labels can be added to metrics via the following mechanisms:

lib/promscrape/client.go

@@ -14,19 +14,24 @@ import (
 var (
 	maxScrapeSize = flag.Int("promscrape.maxScrapeSize", 16*1024*1024, "The maximum size of scrape response in bytes to process from Prometheus targets. "+
 		"Bigger responses are rejected")
-	disableCompression = flag.Bool("promscrape.disableCompression", false, "Whether to disable sending 'Accept-Encoding: gzip' request headers to scrape targets. "+
-		"This may reduce CPU usage on scrape targets at the cost of higher network bandwidth utilization")
-	disableKeepAlive = flag.Bool("promscrape.disableKeepAlive", false, "Whether to disable HTTP keep-alive connections when scraping targets. This may be useful when targets "+
-		"has no support for HTTP keep-alive connection. Note that disabling HTTP keep-alive may increase load on both vmagent and scrape targets")
+	disableCompression = flag.Bool("promscrape.disableCompression", false, "Whether to disable sending 'Accept-Encoding: gzip' request headers to all the scrape targets. "+
+		"This may reduce CPU usage on scrape targets at the cost of higher network bandwidth utilization. "+
+		"It is possible to set 'disable_compression: true' individually per each 'scrape_config' section in '-promscrape.config' for fine grained control")
+	disableKeepAlive = flag.Bool("promscrape.disableKeepAlive", false, "Whether to disable HTTP keep-alive connections when scraping all the targets. "+
+		"This may be useful when targets has no support for HTTP keep-alive connection. "+
+		"It is possible to set `disable_keepalive: true` individually per each 'scrape_config` section in '-promscrape.config' for fine grained control. "+
+		"Note that disabling HTTP keep-alive may increase load on both vmagent and scrape targets")
 )
 
 type client struct {
 	hc *fasthttp.HostClient
 
-	scrapeURL  string
-	host       string
-	requestURI string
-	authHeader string
+	scrapeURL          string
+	host               string
+	requestURI         string
+	authHeader         string
+	disableCompression bool
+	disableKeepAlive   bool
 }
 
 func newClient(sw *ScrapeWork) *client {
@@ -61,10 +66,12 @@ func newClient(sw *ScrapeWork) *client {
 	return &client{
 		hc: hc,
 
-		scrapeURL:  sw.ScrapeURL,
-		host:       host,
-		requestURI: requestURI,
-		authHeader: sw.AuthConfig.Authorization,
+		scrapeURL:          sw.ScrapeURL,
+		host:               host,
+		requestURI:         requestURI,
+		authHeader:         sw.AuthConfig.Authorization,
+		disableCompression: sw.DisableCompression,
+		disableKeepAlive:   sw.DisableKeepAlive,
 	}
 }
 
@@ -72,10 +79,10 @@ func (c *client) ReadData(dst []byte) ([]byte, error) {
 	req := fasthttp.AcquireRequest()
 	req.SetRequestURI(c.requestURI)
 	req.SetHost(c.host)
-	if !*disableCompression {
+	if !*disableCompression || c.disableCompression {
 		req.Header.Set("Accept-Encoding", "gzip")
 	}
-	if *disableKeepAlive {
+	if *disableKeepAlive || c.disableKeepAlive {
 		req.SetConnectionClose()
 	}
 	if c.authHeader != "" {

lib/promscrape/config.go

@@ -76,6 +76,10 @@ type ScrapeConfig struct {
 	MetricRelabelConfigs []promrelabel.RelabelConfig `yaml:"metric_relabel_configs"`
 	SampleLimit          int                         `yaml:"sample_limit"`
 
+	// These options are supported only by lib/promscrape.
+	DisableCompression bool `yaml:"disable_compression"`
+	DisableKeepAlive   bool `yaml:"disable_keepalive"`
+
 	// This is set in loadConfig
 	swc *scrapeWorkConfig
 }
@@ -404,6 +408,8 @@ func getScrapeWorkConfig(sc *ScrapeConfig, baseDir string, globalCfg *GlobalConf
 		relabelConfigs:       relabelConfigs,
 		metricRelabelConfigs: metricRelabelConfigs,
 		sampleLimit:          sc.SampleLimit,
+		disableCompression:   sc.DisableCompression,
+		disableKeepAlive:     sc.DisableKeepAlive,
 	}
 	return swc, nil
 }
@@ -422,6 +428,8 @@ type scrapeWorkConfig struct {
 	relabelConfigs       []promrelabel.ParsedRelabelConfig
 	metricRelabelConfigs []promrelabel.ParsedRelabelConfig
 	sampleLimit          int
+	disableCompression   bool
+	disableKeepAlive     bool
 }
 
 func appendKubernetesScrapeWork(dst []ScrapeWork, sdc *kubernetes.SDConfig, baseDir string, swc *scrapeWorkConfig) ([]ScrapeWork, bool) {
@@ -602,6 +610,8 @@ func appendScrapeWork(dst []ScrapeWork, swc *scrapeWorkConfig, target string, ex
 		AuthConfig:           swc.authConfig,
 		MetricRelabelConfigs: swc.metricRelabelConfigs,
 		SampleLimit:          swc.sampleLimit,
+		DisableCompression:   swc.disableCompression,
+		DisableKeepAlive:     swc.disableKeepAlive,
 
 		jobNameOriginal: swc.jobName,
 	})

lib/promscrape/config_test.go

@@ -1201,6 +1201,9 @@ scrape_configs:
 	f(`
 scrape_configs:
   - job_name: 'snmp'
+    sample_limit: 100
+    disable_keepalive: true
+    disable_compression: true
     static_configs:
       - targets:
         - 192.168.1.2  # SNMP device.
@@ -1249,8 +1252,11 @@ scrape_configs:
 					Value: "snmp",
 				},
 			},
-			AuthConfig:      &promauth.Config{},
-			jobNameOriginal: "snmp",
+			AuthConfig:         &promauth.Config{},
+			SampleLimit:        100,
+			DisableKeepAlive:   true,
+			DisableCompression: true,
+			jobNameOriginal:    "snmp",
 		},
 	})
 }

lib/promscrape/scrapework.go

@@ -67,6 +67,12 @@ type ScrapeWork struct {
 	// The maximum number of metrics to scrape after relabeling.
 	SampleLimit int
 
+	// Whether to disable response compression when querying ScrapeURL.
+	DisableCompression bool
+
+	// Whether to disable HTTP keep-alive when querying ScrapeURL.
+	DisableKeepAlive bool
+
 	// The original 'job_name'
 	jobNameOriginal string
 }
@@ -76,9 +82,9 @@ type ScrapeWork struct {
 // it can be used for comparing for equality two ScrapeWork objects.
 func (sw *ScrapeWork) key() string {
 	key := fmt.Sprintf("ScrapeURL=%s, ScrapeInterval=%s, ScrapeTimeout=%s, HonorLabels=%v, HonorTimestamps=%v, Labels=%s, "+
-		"AuthConfig=%s, MetricRelabelConfigs=%s, SampleLimit=%d",
+		"AuthConfig=%s, MetricRelabelConfigs=%s, SampleLimit=%d, DisableCompression=%v, DisableKeepAlive=%v",
 		sw.ScrapeURL, sw.ScrapeInterval, sw.ScrapeTimeout, sw.HonorLabels, sw.HonorTimestamps, sw.LabelsString(),
-		sw.AuthConfig.String(), sw.metricRelabelConfigsString(), sw.SampleLimit)
+		sw.AuthConfig.String(), sw.metricRelabelConfigsString(), sw.SampleLimit, sw.DisableCompression, sw.DisableKeepAlive)
 	return key
 }