Added ability to specify scrape protocols to accept during HTTP content type negotiation. (#12738)

* Added ability to specify scrape protocols to accept during HTTP content type negotiation.


This is done via new option in GlobalConfig and ScrapeConfig: "scrape_protocol"

Signed-off-by: bwplotka <bwplotka@gmail.com>

* Fixed readability and log message.

Signed-off-by: bwplotka <bwplotka@gmail.com>

---------

Signed-off-by: bwplotka <bwplotka@gmail.com>

cmd/prometheus/main.go

@@ -202,8 +202,9 @@ func (c *flagConfig) setFeatureListOptions(logger log.Logger) error {
 				level.Info(logger).Log("msg", "No default port will be appended to scrape targets' addresses.")
 			case "native-histograms":
 				c.tsdb.EnableNativeHistograms = true
-				c.scrape.EnableProtobufNegotiation = true
+				// Change global variable. Hacky, but it's hard to pass new option or default to unmarshaller.
-				level.Info(logger).Log("msg", "Experimental native histogram support enabled.")
+				config.DefaultConfig.GlobalConfig.ScrapeProtocols = config.DefaultNativeHistogramScrapeProtocols
+				level.Info(logger).Log("msg", "Experimental native histogram support enabled. Changed default scrape_protocols to prefer PrometheusProto format.", "global.scrape_protocols", fmt.Sprintf("%v", config.DefaultConfig.GlobalConfig.ScrapeProtocols))
 			case "":
 				continue
 			case "promql-at-modifier", "promql-negative-offset":

config/config.go

@@ -19,6 +19,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"time"
 
@@ -143,12 +144,14 @@ var (
 		ScrapeInterval:     model.Duration(1 * time.Minute),
 		ScrapeTimeout:      model.Duration(10 * time.Second),
 		EvaluationInterval: model.Duration(1 * time.Minute),
+		// When native histogram feature flag is enabled, ScrapeProtocols default
+		// changes to DefaultNativeHistogramScrapeProtocols.
+		ScrapeProtocols: DefaultScrapeProtocols,
 	}
 
 	// DefaultScrapeConfig is the default scrape configuration.
 	DefaultScrapeConfig = ScrapeConfig{
-		// ScrapeTimeout and ScrapeInterval default to the configured
+		// ScrapeTimeout, ScrapeInterval and ScrapeProtocols default to the configured globals.
-		// globals.
 		ScrapeClassicHistograms: false,
 		MetricsPath:             "/metrics",
 		Scheme:                  "http",
@@ -260,7 +263,7 @@ func (c Config) String() string {
 	return string(b)
 }
 
-// ScrapeConfigs returns the scrape configurations.
+// GetScrapeConfigs returns the scrape configurations.
 func (c *Config) GetScrapeConfigs() ([]*ScrapeConfig, error) {
 	scfgs := make([]*ScrapeConfig, len(c.ScrapeConfigs))
 
@@ -385,6 +388,11 @@ type GlobalConfig struct {
 	ScrapeInterval model.Duration `yaml:"scrape_interval,omitempty"`
 	// The default timeout when scraping targets.
 	ScrapeTimeout model.Duration `yaml:"scrape_timeout,omitempty"`
+	// The protocols to negotiate during a scrape. It tells clients what
+	// protocol are accepted by Prometheus and with what weight (most wanted is first).
+	// Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
+	// OpenMetricsText1.0.0, PrometheusText0.0.4.
+	ScrapeProtocols []ScrapeProtocol `yaml:"scrape_protocols,omitempty"`
 	// How frequently to evaluate rules by default.
 	EvaluationInterval model.Duration `yaml:"evaluation_interval,omitempty"`
 	// File to which PromQL queries are logged.
@@ -414,6 +422,68 @@ type GlobalConfig struct {
 	KeepDroppedTargets uint `yaml:"keep_dropped_targets,omitempty"`
 }
 
+// ScrapeProtocol represents supported protocol for scraping metrics.
+type ScrapeProtocol string
+
+// Validate returns error if given scrape protocol is not supported.
+func (s ScrapeProtocol) Validate() error {
+	if _, ok := ScrapeProtocolsHeaders[s]; !ok {
+		return fmt.Errorf("unknown scrape protocol %v, supported: %v",
+			s, func() (ret []string) {
+				for k := range ScrapeProtocolsHeaders {
+					ret = append(ret, string(k))
+				}
+				sort.Strings(ret)
+				return ret
+			}())
+	}
+	return nil
+}
+
+var (
+	PrometheusProto      ScrapeProtocol = "PrometheusProto"
+	PrometheusText0_0_4  ScrapeProtocol = "PrometheusText0.0.4"
+	OpenMetricsText0_0_1 ScrapeProtocol = "OpenMetricsText0.0.1"
+	OpenMetricsText1_0_0 ScrapeProtocol = "OpenMetricsText1.0.0"
+
+	ScrapeProtocolsHeaders = map[ScrapeProtocol]string{
+		PrometheusProto:      "application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited",
+		PrometheusText0_0_4:  "text/plain;version=0.0.4",
+		OpenMetricsText0_0_1: "application/openmetrics-text;version=0.0.1",
+		OpenMetricsText1_0_0: "application/openmetrics-text;version=1.0.0",
+	}
+
+	DefaultScrapeProtocols = []ScrapeProtocol{
+		OpenMetricsText1_0_0,
+		OpenMetricsText0_0_1,
+		PrometheusText0_0_4,
+	}
+	DefaultNativeHistogramScrapeProtocols = []ScrapeProtocol{
+		PrometheusProto,
+		OpenMetricsText1_0_0,
+		OpenMetricsText0_0_1,
+		PrometheusText0_0_4,
+	}
+)
+
+// validateAcceptScrapeProtocols return errors if we see problems with accept scrape protocols option.
+func validateAcceptScrapeProtocols(sps []ScrapeProtocol) error {
+	if len(sps) == 0 {
+		return errors.New("scrape_protocols cannot be empty")
+	}
+	dups := map[string]struct{}{}
+	for _, sp := range sps {
+		if _, ok := dups[strings.ToLower(string(sp))]; ok {
+			return fmt.Errorf("duplicated protocol in scrape_protocols, got %v", sps)
+		}
+		if err := sp.Validate(); err != nil {
+			return fmt.Errorf("scrape_protocols: %w", err)
+		}
+		dups[strings.ToLower(string(sp))] = struct{}{}
+	}
+	return nil
+}
+
 // SetDirectory joins any relative file paths with dir.
 func (c *GlobalConfig) SetDirectory(dir string) {
 	c.QueryLogFile = config.JoinDir(dir, c.QueryLogFile)
@@ -459,6 +529,14 @@ func (c *GlobalConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	if gc.EvaluationInterval == 0 {
 		gc.EvaluationInterval = DefaultGlobalConfig.EvaluationInterval
 	}
+
+	if gc.ScrapeProtocols == nil {
+		gc.ScrapeProtocols = DefaultGlobalConfig.ScrapeProtocols
+	}
+	if err := validateAcceptScrapeProtocols(gc.ScrapeProtocols); err != nil {
+		return fmt.Errorf("%w for global config", err)
+	}
+
 	*c = *gc
 	return nil
 }
@@ -469,7 +547,8 @@ func (c *GlobalConfig) isZero() bool {
 		c.ScrapeInterval == 0 &&
 		c.ScrapeTimeout == 0 &&
 		c.EvaluationInterval == 0 &&
-		c.QueryLogFile == ""
+		c.QueryLogFile == "" &&
+		c.ScrapeProtocols == nil
 }
 
 type ScrapeConfigs struct {
@@ -490,6 +569,11 @@ type ScrapeConfig struct {
 	ScrapeInterval model.Duration `yaml:"scrape_interval,omitempty"`
 	// The timeout for scraping targets of this config.
 	ScrapeTimeout model.Duration `yaml:"scrape_timeout,omitempty"`
+	// The protocols to negotiate during a scrape. It tells clients what
+	// protocol are accepted by Prometheus and with what preference (most wanted is first).
+	// Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
+	// OpenMetricsText1.0.0, PrometheusText0.0.4.
+	ScrapeProtocols []ScrapeProtocol `yaml:"scrape_protocols,omitempty"`
 	// Whether to scrape a classic histogram that is also exposed as a native histogram.
 	ScrapeClassicHistograms bool `yaml:"scrape_classic_histograms,omitempty"`
 	// The HTTP resource path on which to fetch metrics from targets.
@@ -577,6 +661,7 @@ func (c *ScrapeConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	return nil
 }
 
+// Validate validates scrape config, but also fills relevant default values from global config if needed.
 func (c *ScrapeConfig) Validate(globalConfig GlobalConfig) error {
 	if c == nil {
 		return errors.New("empty or null scrape config section")
@@ -618,6 +703,13 @@ func (c *ScrapeConfig) Validate(globalConfig GlobalConfig) error {
 		c.KeepDroppedTargets = globalConfig.KeepDroppedTargets
 	}
 
+	if c.ScrapeProtocols == nil {
+		c.ScrapeProtocols = globalConfig.ScrapeProtocols
+	}
+	if err := validateAcceptScrapeProtocols(c.ScrapeProtocols); err != nil {
+		return fmt.Errorf("%w for scrape config with job name %q", err, c.JobName)
+	}
+
 	return nil
 }
 

config/config_test.go

@@ -92,6 +92,7 @@ var expectedConf = &Config{
 		LabelLimit:            globLabelLimit,
 		LabelNameLengthLimit:  globLabelNameLengthLimit,
 		LabelValueLengthLimit: globLabelValueLengthLimit,
+		ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 	},
 
 	RuleFiles: []string{
@@ -191,6 +192,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath: DefaultScrapeConfig.MetricsPath,
 			Scheme:      DefaultScrapeConfig.Scheme,
@@ -292,6 +294,7 @@ var expectedConf = &Config{
 			LabelLimit:            35,
 			LabelNameLengthLimit:  210,
 			LabelValueLengthLimit: 210,
+			ScrapeProtocols:       []ScrapeProtocol{PrometheusText0_0_4},
 
 			HTTPClientConfig: config.HTTPClientConfig{
 				BasicAuth: &config.BasicAuth{
@@ -387,6 +390,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -440,6 +444,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath: "/metrics",
 			Scheme:      "http",
@@ -471,6 +476,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -508,6 +514,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath: DefaultScrapeConfig.MetricsPath,
 			Scheme:      DefaultScrapeConfig.Scheme,
@@ -545,6 +552,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -571,6 +579,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -606,6 +615,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -638,6 +648,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -677,6 +688,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -706,6 +718,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -738,6 +751,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -763,6 +777,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -791,6 +806,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      "/federate",
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -819,6 +835,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -847,6 +864,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -872,6 +890,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -905,6 +924,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -937,6 +957,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -965,6 +986,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -993,6 +1015,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1025,6 +1048,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1060,6 +1084,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1114,6 +1139,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1139,6 +1165,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			HTTPClientConfig: config.DefaultHTTPClientConfig,
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
@@ -1175,6 +1202,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			HTTPClientConfig: config.DefaultHTTPClientConfig,
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
@@ -1217,6 +1245,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1250,6 +1279,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			HTTPClientConfig: config.DefaultHTTPClientConfig,
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
@@ -1277,6 +1307,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1307,6 +1338,7 @@ var expectedConf = &Config{
 			LabelLimit:            globLabelLimit,
 			LabelNameLengthLimit:  globLabelNameLengthLimit,
 			LabelValueLengthLimit: globLabelValueLengthLimit,
+			ScrapeProtocols:       DefaultGlobalConfig.ScrapeProtocols,
 
 			MetricsPath:      DefaultScrapeConfig.MetricsPath,
 			Scheme:           DefaultScrapeConfig.Scheme,
@@ -1925,6 +1957,14 @@ var expectedErrors = []struct {
 		filename: "scrape_config_files_glob.bad.yml",
 		errMsg:   `parsing YAML file testdata/scrape_config_files_glob.bad.yml: invalid scrape config file path "scrape_configs/*/*"`,
 	},
+	{
+		filename: "scrape_config_files_scrape_protocols.bad.yml",
+		errMsg:   `parsing YAML file testdata/scrape_config_files_scrape_protocols.bad.yml: scrape_protocols: unknown scrape protocol prometheusproto, supported: [OpenMetricsText0.0.1 OpenMetricsText1.0.0 PrometheusProto PrometheusText0.0.4] for scrape config with job name "node"`,
+	},
+	{
+		filename: "scrape_config_files_scrape_protocols2.bad.yml",
+		errMsg:   `parsing YAML file testdata/scrape_config_files_scrape_protocols2.bad.yml: duplicated protocol in scrape_protocols, got [OpenMetricsText1.0.0 PrometheusProto OpenMetricsText1.0.0] for scrape config with job name "node"`,
+	},
 }
 
 func TestBadConfigs(t *testing.T) {
@@ -2018,6 +2058,8 @@ func TestGetScrapeConfigs(t *testing.T) {
 			HonorTimestamps: true,
 			ScrapeInterval:  scrapeInterval,
 			ScrapeTimeout:   scrapeTimeout,
+			ScrapeProtocols: DefaultGlobalConfig.ScrapeProtocols,
+
 			MetricsPath:      "/metrics",
 			Scheme:           "http",
 			HTTPClientConfig: config.DefaultHTTPClientConfig,
@@ -2071,6 +2113,7 @@ func TestGetScrapeConfigs(t *testing.T) {
 					HonorTimestamps: true,
 					ScrapeInterval:  model.Duration(60 * time.Second),
 					ScrapeTimeout:   DefaultGlobalConfig.ScrapeTimeout,
+					ScrapeProtocols: DefaultGlobalConfig.ScrapeProtocols,
 
 					MetricsPath: DefaultScrapeConfig.MetricsPath,
 					Scheme:      DefaultScrapeConfig.Scheme,
@@ -2101,6 +2144,8 @@ func TestGetScrapeConfigs(t *testing.T) {
 					HonorTimestamps: true,
 					ScrapeInterval:  model.Duration(15 * time.Second),
 					ScrapeTimeout:   DefaultGlobalConfig.ScrapeTimeout,
+					ScrapeProtocols: DefaultGlobalConfig.ScrapeProtocols,
+
 					HTTPClientConfig: config.HTTPClientConfig{
 						TLSConfig: config.TLSConfig{
 							CertFile: filepath.FromSlash("testdata/valid_cert_file"),

config/testdata/conf.good.yml

@@ -114,6 +114,7 @@ scrape_configs:
 
     scrape_interval: 50s
     scrape_timeout: 5s
+    scrape_protocols: ["PrometheusText0.0.4"]
 
     body_size_limit: 10MB
     sample_limit: 1000
@@ -122,7 +123,6 @@ scrape_configs:
     label_name_length_limit: 210
     label_value_length_limit: 210
 
-
     metrics_path: /my_path
     scheme: https
 

config/testdata/scrape_config_files_scrape_protocols.bad.yml

@@ -0,0 +1,5 @@
+scrape_configs:
+  - job_name: node
+    scrape_protocols: ["prometheusproto"]
+    static_configs:
+      - targets: ['localhost:8080']

config/testdata/scrape_config_files_scrape_protocols2.bad.yml

@@ -0,0 +1,5 @@
+scrape_configs:
+  - job_name: node
+    scrape_protocols: ["OpenMetricsText1.0.0", "PrometheusProto", "OpenMetricsText1.0.0"]
+    static_configs:
+      - targets: ['localhost:8080']

docs/configuration/configuration.md

@@ -61,6 +61,13 @@ global:
   # How long until a scrape request times out.
   [ scrape_timeout: <duration> | default = 10s ]
 
+  # The protocols to negotiate during a scrape with the client.
+  # Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
+  # OpenMetricsText1.0.0, PrometheusText0.0.4.
+  # The default value changes to [ PrometheusProto, OpenMetricsText1.0.0, OpenMetricsText0.0.1, PrometheusText0.0.4 ]
+  # when native_histogram feature flag is set.
+  [ scrape_protocols: [<string>, ...] | default = [ OpenMetricsText1.0.0, OpenMetricsText0.0.1, PrometheusText0.0.4 ] ]
+
   # How frequently to evaluate rules.
   [ evaluation_interval: <duration> | default = 1m ]
 
@@ -171,6 +178,11 @@ job_name: <job_name>
 # Per-scrape timeout when scraping this job.
 [ scrape_timeout: <duration> | default = <global_config.scrape_timeout> ]
 
+# The protocols to negotiate during a scrape with the client.
+# Supported values (case sensitive): PrometheusProto, OpenMetricsText0.0.1,
+# OpenMetricsText1.0.0, PrometheusText0.0.4.
+[ scrape_protocols: [<string>, ...] | default = <global_config.scrape_protocols> ]
+
 # Whether to scrape a classic histogram that is also exposed as a native
 # histogram (has no effect without --enable-feature=native-histograms).
 [ scrape_classic_histograms: <boolean> | default = false ]

scrape/manager.go

@@ -132,9 +132,6 @@ type Options struct {
 	// Option to enable the experimental in-memory metadata storage and append
 	// metadata to the WAL.
 	EnableMetadataStorage bool
-	// Option to enable protobuf negotiation with the client. Note that the client can already
-	// send protobuf without needing to enable this.
-	EnableProtobufNegotiation bool
 	// Option to increase the interval used by scrape manager to throttle target groups updates.
 	DiscoveryReloadInterval model.Duration
 

scrape/scrape.go

@@ -24,6 +24,7 @@ import (
 	"net/http"
 	"reflect"
 	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -250,8 +251,6 @@ type scrapePool struct {
 	newLoop func(scrapeLoopOptions) loop
 
 	noDefaultPort bool
-
-	enableProtobufNegotiation bool
 }
 
 type labelLimits struct {
@@ -305,7 +304,6 @@ func newScrapePool(cfg *config.ScrapeConfig, app storage.Appendable, offsetSeed
 		logger:        logger,
 		httpOpts:      options.HTTPClientOptions,
 		noDefaultPort: options.NoDefaultPort,
-		enableProtobufNegotiation: options.EnableProtobufNegotiation,
 	}
 	sp.newLoop = func(opts scrapeLoopOptions) loop {
 		// Update the targets retrieval function for metadata to a new scrape cache.
@@ -456,12 +454,14 @@ func (sp *scrapePool) reload(cfg *config.ScrapeConfig) error {
 
 		t := sp.activeTargets[fp]
 		interval, timeout, err := t.intervalAndTimeout(interval, timeout)
-		acceptHeader := scrapeAcceptHeader
-		if sp.enableProtobufNegotiation {
-			acceptHeader = scrapeAcceptHeaderWithProtobuf
-		}
 		var (
-			s       = &targetScraper{Target: t, client: sp.client, timeout: timeout, bodySizeLimit: bodySizeLimit, acceptHeader: acceptHeader}
+			s = &targetScraper{
+				Target:        t,
+				client:        sp.client,
+				timeout:       timeout,
+				bodySizeLimit: bodySizeLimit,
+				acceptHeader:  acceptHeader(cfg.ScrapeProtocols),
+			}
 			newLoop = sp.newLoop(scrapeLoopOptions{
 				target:          t,
 				scraper:         s,
@@ -577,11 +577,13 @@ func (sp *scrapePool) sync(targets []*Target) {
 			// for every target.
 			var err error
 			interval, timeout, err = t.intervalAndTimeout(interval, timeout)
-			acceptHeader := scrapeAcceptHeader
+			s := &targetScraper{
-			if sp.enableProtobufNegotiation {
+				Target:        t,
-				acceptHeader = scrapeAcceptHeaderWithProtobuf
+				client:        sp.client,
+				timeout:       timeout,
+				bodySizeLimit: bodySizeLimit,
+				acceptHeader:  acceptHeader(sp.config.ScrapeProtocols),
 			}
-			s := &targetScraper{Target: t, client: sp.client, timeout: timeout, bodySizeLimit: bodySizeLimit, acceptHeader: acceptHeader}
 			l := sp.newLoop(scrapeLoopOptions{
 				target:                  t,
 				scraper:                 s,
@@ -808,10 +810,20 @@ type targetScraper struct {
 
 var errBodySizeLimit = errors.New("body size limit exceeded")
 
-const (
+// acceptHeader transforms preference from the options into specific header values as
-	scrapeAcceptHeader             = `application/openmetrics-text;version=1.0.0,application/openmetrics-text;version=0.0.1;q=0.75,text/plain;version=0.0.4;q=0.5,*/*;q=0.1`
+// https://www.rfc-editor.org/rfc/rfc9110.html#name-accept defines.
-	scrapeAcceptHeaderWithProtobuf = `application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited,application/openmetrics-text;version=1.0.0;q=0.8,application/openmetrics-text;version=0.0.1;q=0.75,text/plain;version=0.0.4;q=0.5,*/*;q=0.1`
+// No validation is here, we expect scrape protocols to be validated already.
-)
+func acceptHeader(sps []config.ScrapeProtocol) string {
+	var vals []string
+	weight := len(config.ScrapeProtocolsHeaders) + 1
+	for _, sp := range sps {
+		vals = append(vals, fmt.Sprintf("%s;q=0.%d", config.ScrapeProtocolsHeaders[sp], weight))
+		weight--
+	}
+	// Default match anything.
+	vals = append(vals, fmt.Sprintf("*/*;q=%d", weight))
+	return strings.Join(vals, ",")
+}
 
 var UserAgent = fmt.Sprintf("Prometheus/%s", version.Version)
 

scrape/scrape_test.go

@@ -2627,9 +2627,9 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 		require.Equal(t, "metric_a 1\nmetric_b 2\n", buf.String())
 	}
 
-	runTest(scrapeAcceptHeader)
+	runTest(acceptHeader(config.DefaultScrapeProtocols))
 	protobufParsing = true
-	runTest(scrapeAcceptHeaderWithProtobuf)
+	runTest(acceptHeader(config.DefaultNativeHistogramScrapeProtocols))
 }
 
 func TestTargetScrapeScrapeCancel(t *testing.T) {
@@ -2655,7 +2655,7 @@ func TestTargetScrapeScrapeCancel(t *testing.T) {
 			),
 		},
 		client:       http.DefaultClient,
-		acceptHeader: scrapeAcceptHeader,
+		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
 	}
 	ctx, cancel := context.WithCancel(context.Background())
 
@@ -2710,7 +2710,7 @@ func TestTargetScrapeScrapeNotFound(t *testing.T) {
 			),
 		},
 		client:       http.DefaultClient,
-		acceptHeader: scrapeAcceptHeader,
+		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
 	}
 
 	resp, err := ts.scrape(context.Background())
@@ -2754,7 +2754,7 @@ func TestTargetScraperBodySizeLimit(t *testing.T) {
 		},
 		client:        http.DefaultClient,
 		bodySizeLimit: bodySizeLimit,
-		acceptHeader:  scrapeAcceptHeader,
+		acceptHeader:  acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
 	}
 	var buf bytes.Buffer