feat(utf8): utf8 content negotation and flags

Signed-off-by: Owen Williams <owen.williams@grafana.com>

cmd/prometheus/main.go

@@ -152,6 +152,7 @@ type flagConfig struct {
 	queryConcurrency    int
 	queryMaxSamples     int
 	RemoteFlushDeadline model.Duration
+	nameEscapingScheme  string
 
 	featureList   []string
 	memlimitRatio float64
@@ -237,6 +238,9 @@ func (c *flagConfig) setFeatureListOptions(logger log.Logger) error {
 			case "delayed-compaction":
 				c.tsdb.EnableDelayedCompaction = true
 				level.Info(logger).Log("msg", "Experimental delayed compaction is enabled.")
+			case "utf8-names":
+				model.NameValidationScheme = model.UTF8Validation
+				level.Info(logger).Log("msg", "Experimental UTF-8 support enabled")
 			case "":
 				continue
 			case "promql-at-modifier", "promql-negative-offset":
@@ -481,7 +485,9 @@ func main() {
 	a.Flag("scrape.discovery-reload-interval", "Interval used by scrape manager to throttle target groups updates.").
 		Hidden().Default("5s").SetValue(&cfg.scrape.DiscoveryReloadInterval)
 
-	a.Flag("enable-feature", "Comma separated feature names to enable. Valid options: agent, auto-gomemlimit, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-per-step-stats, promql-experimental-functions, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs, no-default-scrape-port, native-histograms, otlp-write-receiver, created-timestamp-zero-ingestion, concurrent-rule-eval, delayed-compaction. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details.").
+	a.Flag("scrape.name-escaping-scheme", `Method for escaping legacy invalid names when sending to Prometheus that does not support UTF-8. Can be one of "values", "underscores", or "dots".`).Default(scrape.DefaultNameEscapingScheme.String()).StringVar(&cfg.nameEscapingScheme)
+
+	a.Flag("enable-feature", "Comma separated feature names to enable. Valid options: agent, auto-gomemlimit, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-per-step-stats, promql-experimental-functions, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs, no-default-scrape-port, native-histograms, otlp-write-receiver, created-timestamp-zero-ingestion, concurrent-rule-eval, delayed-compaction, utf8-names. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details.").
 		Default("").StringsVar(&cfg.featureList)
 
 	promlogflag.AddFlags(a, &cfg.promlogConfig)
@@ -509,6 +515,15 @@ func main() {
 		os.Exit(1)
 	}
 
+	if cfg.nameEscapingScheme != "" {
+		scheme, err := model.ToEscapingScheme(cfg.nameEscapingScheme)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, `Invalid name escaping scheme: %q; Needs to be one of "values", "underscores", or "dots"`, cfg.nameEscapingScheme)
+			os.Exit(1)
+		}
+		model.NameEscapingScheme = scheme
+	}
+
 	if agentMode && len(serverOnlyFlags) > 0 {
 		fmt.Fprintf(os.Stderr, "The following flag(s) can not be used in agent mode: %q", serverOnlyFlags)
 		os.Exit(3)

config/config.go

@@ -67,6 +67,11 @@ var (
 	}
 )
 
+const (
+	LegacyValidationConfig = "legacy"
+	UTF8ValidationConfig   = "utf8"
+)
+
 // Load parses the YAML input s into a Config.
 func Load(s string, expandExternalLabels bool, logger log.Logger) (*Config, error) {
 	cfg := &Config{}
@@ -446,6 +451,8 @@ type GlobalConfig struct {
 	// Keep no more than this many dropped targets per job.
 	// 0 means no limit.
 	KeepDroppedTargets uint `yaml:"keep_dropped_targets,omitempty"`
+	// Allow UTF8 Metric and Label Names.
+	MetricNameValidationScheme string `yaml:"metric_name_validation_scheme,omitempty"`
 }
 
 // ScrapeProtocol represents supported protocol for scraping metrics.
@@ -471,6 +478,7 @@ var (
 	PrometheusText0_0_4  ScrapeProtocol = "PrometheusText0.0.4"
 	OpenMetricsText0_0_1 ScrapeProtocol = "OpenMetricsText0.0.1"
 	OpenMetricsText1_0_0 ScrapeProtocol = "OpenMetricsText1.0.0"
+	UTF8NamesHeader      string         = model.EscapingKey + "=" + model.AllowUTF8
 
 	ScrapeProtocolsHeaders = map[ScrapeProtocol]string{
 		PrometheusProto:      "application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited",
@@ -656,6 +664,8 @@ type ScrapeConfig struct {
 	// Keep no more than this many dropped targets per job.
 	// 0 means no limit.
 	KeepDroppedTargets uint `yaml:"keep_dropped_targets,omitempty"`
+	// Allow UTF8 Metric and Label Names.
+	MetricNameValidationScheme string `yaml:"metric_name_validation_scheme,omitempty"`
 
 	// We cannot do proper Go type embedding below as the parser will then parse
 	// values arbitrarily into the overflow maps of further-down types.
@@ -762,6 +772,17 @@ func (c *ScrapeConfig) Validate(globalConfig GlobalConfig) error {
 		return fmt.Errorf("%w for scrape config with job name %q", err, c.JobName)
 	}
 
+	switch globalConfig.MetricNameValidationScheme {
+	case "", LegacyValidationConfig:
+	case UTF8ValidationConfig:
+		if model.NameValidationScheme != model.UTF8Validation {
+			return fmt.Errorf("utf8 name validation requested but feature not enabled via --enable-feature=utf8-names")
+		}
+	default:
+		return fmt.Errorf("unknown name validation method specified, must be either 'legacy' or 'utf8', got %s", globalConfig.MetricNameValidationScheme)
+	}
+	c.MetricNameValidationScheme = globalConfig.MetricNameValidationScheme
+
 	return nil
 }
 

docs/command-line/prometheus.md

@@ -56,7 +56,8 @@ The Prometheus monitoring server
 | <code class="text-nowrap">--query.timeout</code> | Maximum time a query may take before being aborted. Use with server mode only. | `2m` |
 | <code class="text-nowrap">--query.max-concurrency</code> | Maximum number of queries executed concurrently. Use with server mode only. | `20` |
 | <code class="text-nowrap">--query.max-samples</code> | Maximum number of samples a single query can load into memory. Note that queries will fail if they try to load more samples than this into memory, so this also limits the number of samples a query can return. Use with server mode only. | `50000000` |
-| <code class="text-nowrap">--enable-feature</code> | Comma separated feature names to enable. Valid options: agent, auto-gomemlimit, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-per-step-stats, promql-experimental-functions, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs, no-default-scrape-port, native-histograms, otlp-write-receiver, created-timestamp-zero-ingestion, concurrent-rule-eval, delayed-compaction. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details. |  |
+| <code class="text-nowrap">--scrape.name-escaping-scheme</code> | Method for escaping legacy invalid names when sending to Prometheus that does not support UTF-8. Can be one of "values", "underscores", or "dots". | `values` |
+| <code class="text-nowrap">--enable-feature</code> | Comma separated feature names to enable. Valid options: agent, auto-gomemlimit, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-per-step-stats, promql-experimental-functions, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs, no-default-scrape-port, native-histograms, otlp-write-receiver, created-timestamp-zero-ingestion, concurrent-rule-eval, delayed-compaction, utf8-names. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details. |  |
 | <code class="text-nowrap">--log.level</code> | Only log messages with the given severity or above. One of: [debug, info, warn, error] | `info` |
 | <code class="text-nowrap">--log.format</code> | Output format of log messages. One of: [logfmt, json] | `logfmt` |
 

docs/configuration/configuration.md

@@ -121,6 +121,11 @@ global:
   # that will be kept in memory. 0 means no limit.
   [ keep_dropped_targets: <int> | default = 0 ]
 
+  # Specifies the validation scheme for metric and label names. Either blank or
+  # "legacy" for letters, numbers, colons, and underscores; or "utf8" for full
+  # UTF-8 support.
+  [ metric_name_validation_scheme <string> | default "legacy" ]
+
 runtime:
   # Configure the Go garbage collector GOGC parameter
   # See: https://tip.golang.org/doc/gc-guide#GOGC
@@ -461,6 +466,11 @@ metric_relabel_configs:
 # that will be kept in memory. 0 means no limit.
 [ keep_dropped_targets: <int> | default = 0 ]
 
+# Specifies the validation scheme for metric and label names. Either blank or
+# "legacy" for letters, numbers, colons, and underscores; or "utf8" for full
+# UTF-8 support.
+[ metric_name_validation_scheme <string> | default "legacy" ]
+
 # Limit on total number of positive and negative buckets allowed in a single
 # native histogram. The resolution of a histogram with more buckets will be
 # reduced until the number of buckets is within the limit. If the limit cannot

docs/feature_flags.md

@@ -249,3 +249,11 @@ In the event of multiple consecutive Head compactions being possible, only the f
 Note that during this delay, the Head continues its usual operations, which include serving and appending series.
 
 Despite the delay in compaction, the blocks produced are time-aligned in the same manner as they would be if the delay was not in place.
+
+## UTF-8 Name Support
+
+`--enable-feature=utf8-names`
+
+When enabled, changes the metric and label name validation scheme inside Prometheus to allow the full UTF-8 character set.
+By itself, this flag does not enable the request of UTF-8 names via content negotiation.
+Users will also have to set `metric_name_validation_scheme` in scrape configs to enable the feature either on the global config or on a per-scrape config basis.

scrape/manager.go

@@ -93,6 +93,8 @@ type Options struct {
 	skipOffsetting bool
 }
 
+const DefaultNameEscapingScheme = model.ValueEncodingEscaping
+
 // Manager maintains a set of scrape pools and manages start/stop cycles
 // when receiving new target groups from the discovery manager.
 type Manager struct {

scrape/scrape.go

@@ -303,6 +303,11 @@ func (sp *scrapePool) restartLoops(reuseCache bool) {
 		mrc                      = sp.config.MetricRelabelConfigs
 	)
 
+	validationScheme := model.LegacyValidation
+	if sp.config.MetricNameValidationScheme == config.UTF8ValidationConfig {
+		validationScheme = model.UTF8Validation
+	}
+
 	sp.targetMtx.Lock()
 
 	forcedErr := sp.refreshTargetLimitErr()
@@ -323,7 +328,7 @@ func (sp *scrapePool) restartLoops(reuseCache bool) {
 				client:               sp.client,
 				timeout:              timeout,
 				bodySizeLimit:        bodySizeLimit,
-				acceptHeader:         acceptHeader(sp.config.ScrapeProtocols),
+				acceptHeader:         acceptHeader(sp.config.ScrapeProtocols, validationScheme),
 				acceptEncodingHeader: acceptEncodingHeader(enableCompression),
 			}
 			newLoop = sp.newLoop(scrapeLoopOptions{
@@ -452,6 +457,11 @@ func (sp *scrapePool) sync(targets []*Target) {
 		scrapeClassicHistograms  = sp.config.ScrapeClassicHistograms
 	)
 
+	validationScheme := model.LegacyValidation
+	if sp.config.MetricNameValidationScheme == config.UTF8ValidationConfig {
+		validationScheme = model.UTF8Validation
+	}
+
 	sp.targetMtx.Lock()
 	for _, t := range targets {
 		hash := t.hash()
@@ -467,7 +477,7 @@ func (sp *scrapePool) sync(targets []*Target) {
 				client:               sp.client,
 				timeout:              timeout,
 				bodySizeLimit:        bodySizeLimit,
-				acceptHeader:         acceptHeader(sp.config.ScrapeProtocols),
+				acceptHeader:         acceptHeader(sp.config.ScrapeProtocols, validationScheme),
 				acceptEncodingHeader: acceptEncodingHeader(enableCompression),
 				metrics:              sp.metrics,
 			}
@@ -714,11 +724,16 @@ var errBodySizeLimit = errors.New("body size limit exceeded")
 // acceptHeader transforms preference from the options into specific header values as
 // https://www.rfc-editor.org/rfc/rfc9110.html#name-accept defines.
 // No validation is here, we expect scrape protocols to be validated already.
-func acceptHeader(sps []config.ScrapeProtocol) string {
+func acceptHeader(sps []config.ScrapeProtocol, scheme model.ValidationScheme) 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))
+		val := config.ScrapeProtocolsHeaders[sp]
+		if scheme == model.UTF8Validation {
+			val += ";" + config.UTF8NamesHeader
+		}
+		val += fmt.Sprintf(";q=0.%d", weight)
+		vals = append(vals, val)
 		weight--
 	}
 	// Default match anything.

scrape/scrape_test.go

@@ -2339,11 +2339,15 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 	)
 
 	var protobufParsing bool
+	var allowUTF8 bool
 
 	server := httptest.NewServer(
 		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			accept := r.Header.Get("Accept")
+			if allowUTF8 {
+				require.Truef(t, strings.Contains(accept, "escaping=allow-utf-8"), "Expected Accept header to allow utf8, got %q", accept)
+			}
 			if protobufParsing {
-				accept := r.Header.Get("Accept")
 				require.True(t, strings.HasPrefix(accept, "application/vnd.google.protobuf;"),
 					"Expected Accept header to prefer application/vnd.google.protobuf.")
 			}
@@ -2351,7 +2355,11 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 			timeout := r.Header.Get("X-Prometheus-Scrape-Timeout-Seconds")
 			require.Equal(t, expectedTimeout, timeout, "Expected scrape timeout header.")
 
-			w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
+			if allowUTF8 {
+				w.Header().Set("Content-Type", `text/plain; version=1.0.0; escaping=allow-utf-8`)
+			} else {
+				w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
+			}
 			w.Write([]byte("metric_a 1\nmetric_b 2\n"))
 		}),
 	)
@@ -2380,13 +2388,22 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 		require.NoError(t, err)
 		contentType, err := ts.readResponse(context.Background(), resp, &buf)
 		require.NoError(t, err)
-		require.Equal(t, "text/plain; version=0.0.4", contentType)
+		if allowUTF8 {
+			require.Equal(t, "text/plain; version=1.0.0; escaping=allow-utf-8", contentType)
+		} else {
+			require.Equal(t, "text/plain; version=0.0.4", contentType)
+		}
 		require.Equal(t, "metric_a 1\nmetric_b 2\n", buf.String())
 	}
 
-	runTest(acceptHeader(config.DefaultScrapeProtocols))
+	runTest(acceptHeader(config.DefaultScrapeProtocols, model.LegacyValidation))
+	protobufParsing = true
+	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.LegacyValidation))
+	protobufParsing = false
+	allowUTF8 = true
+	runTest(acceptHeader(config.DefaultScrapeProtocols, model.UTF8Validation))
 	protobufParsing = true
-	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols))
+	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.UTF8Validation))
 }
 
 func TestTargetScrapeScrapeCancel(t *testing.T) {
@@ -2412,7 +2429,7 @@ func TestTargetScrapeScrapeCancel(t *testing.T) {
 			),
 		},
 		client:       http.DefaultClient,
-		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
+		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
 	}
 	ctx, cancel := context.WithCancel(context.Background())
 
@@ -2467,7 +2484,7 @@ func TestTargetScrapeScrapeNotFound(t *testing.T) {
 			),
 		},
 		client:       http.DefaultClient,
-		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
+		acceptHeader: acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
 	}
 
 	resp, err := ts.scrape(context.Background())
@@ -2511,7 +2528,7 @@ func TestTargetScraperBodySizeLimit(t *testing.T) {
 		},
 		client:        http.DefaultClient,
 		bodySizeLimit: bodySizeLimit,
-		acceptHeader:  acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols),
+		acceptHeader:  acceptHeader(config.DefaultGlobalConfig.ScrapeProtocols, model.LegacyValidation),
 		metrics:       newTestScrapeMetrics(t),
 	}
 	var buf bytes.Buffer