expfmt: add ABNF parser for OpenMetrics 2.0

expfmt/decode.go

@@ -72,6 +72,10 @@ func ResponseFormat(h http.Header) Format {
 			return FmtOpenMetrics_0_0_1
 		case OpenMetricsVersion_1_0_0:
 			return FmtOpenMetrics_1_0_0
+		case OpenMetricsVersion_2_0_0_rc:
+			return FmtOpenMetrics_2_0_0_rc
+		case OpenMetricsVersion_2_0_0:
+			return FmtOpenMetrics_2_0_0
 		default:
 			return FmtUnknown
 		}
@@ -84,9 +88,9 @@ func ResponseFormat(h http.Header) Format {
 // names are validated based on the provided Format -- if the format requires
 // escaping, traditional Prometheus validity checking is used. Otherwise, names
 // are checked for UTF-8 validity. Supported formats include delimited protobuf,
-// Prometheus text format, and OpenMetrics 0.0.1 / 1.0.0. For historical
+// Prometheus text format, and OpenMetrics 0.0.1 / 1.0.0 / 2.0.0-rc / 2.0.0. For historical
 // reasons, this decoder falls back to classic text decoding for other legacy
-// formats, but returns an error for unsupported formats such as OpenMetrics 2.0.
+// formats, and returns an error for unsupported formats such as text protobuf.
 // This decoder may not support the latest features of Prometheus text format
 // and is not intended for high-performance applications.
 // See: https://github.com/prometheus/common/issues/812
@@ -108,6 +112,15 @@ func NewDecoder(r io.Reader, format Format) Decoder {
 		switch params["version"] {
 		case "", OpenMetricsVersion_0_0_1, OpenMetricsVersion_1_0_0:
 			return &openMetricsDecoder{p: newOpenMetricsParser(r, scheme)}
+		case OpenMetricsVersion_2_0_0_rc, OpenMetricsVersion_2_0_0:
+			// format.ToEscapingScheme() defaults to UnderscoreEscaping when no escaping
+			// parameter is set, whereas OpenMetrics 2.0 supports UTF-8 names by default
+			// unless a non-UTF-8 escaping scheme is explicitly requested.
+			om2Scheme := model.UTF8Validation
+			if _, hasEscaping := params[model.EscapingKey]; hasEscaping && format.ToEscapingScheme() != model.NoEscaping {
+				om2Scheme = model.LegacyValidation
+			}
+			return &openMetrics20Decoder{p: newOpenMetrics20Parser(r, om2Scheme)}
 		default:
 			return &errDecoder{err: fmt.Errorf("format %s not supported for decoding", format)}
 		}
@@ -178,6 +191,27 @@ func (d *openMetricsDecoder) Decode(v *dto.MetricFamily) error {
 	return nil
 }
 
+// openMetrics20Decoder implements the Decoder interface for the OpenMetrics 2.0 protocol.
+// Like openMetricsDecoder, it uses goabnf.ParseForest per line without a line-length
+// cap (which has superlinear parse time in line length) and is intended for
+// reference/conformance decoding rather than high-performance or untrusted inputs.
+type openMetrics20Decoder struct {
+	p   *openMetrics20Parser
+	err error
+}
+
+// Decode implements the Decoder interface.
+func (d *openMetrics20Decoder) Decode(v *dto.MetricFamily) error {
+	if d.err != nil {
+		return d.err
+	}
+	if err := d.p.next(v); err != nil {
+		d.err = err
+		return err
+	}
+	return nil
+}
+
 // textDecoder implements the Decoder interface for the text protocol.
 type textDecoder struct {
 	r    io.Reader

expfmt/decode_test.go

@@ -467,6 +467,14 @@ func testDiscriminatorHTTPHeader(t testing.TB) {
 			input:  map[string]string{"Content-Type": `application/openmetrics-text; version=1.0.0`},
 			output: FmtOpenMetrics_1_0_0,
 		},
+		{
+			input:  map[string]string{"Content-Type": `application/openmetrics-text; version=2.0.0-rc`},
+			output: FmtOpenMetrics_2_0_0_rc,
+		},
+		{
+			input:  map[string]string{"Content-Type": `application/openmetrics-text; version=2.0.0`},
+			output: FmtOpenMetrics_2_0_0,
+		},
 		{
 			input:  map[string]string{"Content-Type": `application/openmetrics-text; version=0.0.2`},
 			output: FmtUnknown,
@@ -642,24 +650,26 @@ func TestNewDecoder(t *testing.T) {
 		{
 			name:        "OpenMetrics 2.0.0-rc",
 			format:      om20RCFormat,
-			expectError: true,
+			input:       "# EOF\n",
+			expectError: false,
 		},
 		{
 			name:        "OpenMetrics 2.0.0-rc with escaping",
 			format:      om20RCFormat.WithEscapingScheme(model.ValueEncodingEscaping),
-			expectError: true,
+			input:       "# EOF\n",
+			expectError: false,
 		},
 		{
 			name:        "OpenMetrics 2.0.0",
 			format:      om20Format,
 			input:       "# EOF\n",
-			expectError: true,
+			expectError: false,
 		},
 		{
 			name:        "OpenMetrics 2.0.0 with escaping",
 			format:      om20Format.WithEscapingScheme(model.ValueEncodingEscaping),
 			input:       "# EOF\n",
-			expectError: true,
+			expectError: false,
 		},
 	}
 
@@ -742,3 +752,68 @@ mf1{label="value2"} 42
 	sort.Sort(out)
 	require.Equal(t, out, all)
 }
+
+func TestOpenMetrics20Decoder(t *testing.T) {
+	var (
+		ts = model.Now()
+		in = `# TYPE mf2_total counter
+mf2_total 3
+mf2_total 4
+mf1{label="value1"} -3.14 123.456
+mf1{label="value2"} 42
+# EOF
+`
+		out = model.Vector{
+			&model.Sample{
+				Metric: model.Metric{
+					model.MetricNameLabel: "mf1",
+					"label":               "value1",
+				},
+				Value:     -3.14,
+				Timestamp: 123456,
+			},
+			&model.Sample{
+				Metric: model.Metric{
+					model.MetricNameLabel: "mf1",
+					"label":               "value2",
+				},
+				Value:     42,
+				Timestamp: ts,
+			},
+			&model.Sample{
+				Metric: model.Metric{
+					model.MetricNameLabel: "mf2_total",
+				},
+				Value:     3,
+				Timestamp: ts,
+			},
+			&model.Sample{
+				Metric: model.Metric{
+					model.MetricNameLabel: "mf2_total",
+				},
+				Value:     4,
+				Timestamp: ts,
+			},
+		}
+	)
+
+	dec := &SampleDecoder{
+		Dec: NewDecoder(strings.NewReader(in), FmtOpenMetrics_2_0_0),
+		Opts: &DecodeOptions{
+			Timestamp: ts,
+		},
+	}
+	var all model.Vector
+	for {
+		var smpls model.Vector
+		err := dec.Decode(&smpls)
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		require.NoError(t, err)
+		all = append(all, smpls...)
+	}
+	sort.Sort(all)
+	sort.Sort(out)
+	require.Equal(t, out, all)
+}

expfmt/expfmt.go

@@ -110,7 +110,7 @@ func NewFormat(t FormatType) Format {
 // NewOpenMetricsFormat generates a new OpenMetrics format matching the
 // specified version number.
 //
-// Note: OpenMetrics versions 2.0.0-rc and 2.0.0 are experimental and encode-only (supporting
+// Note: OpenMetrics versions 2.0.0-rc and 2.0.0 are experimental (supporting
 // counter, gauge, summary, untyped, histogram, and gaugehistogram metric types).
 func NewOpenMetricsFormat(version string) (Format, error) {
 	switch version {
@@ -119,10 +119,10 @@ func NewOpenMetricsFormat(version string) (Format, error) {
 	case OpenMetricsVersion_1_0_0:
 		return FmtOpenMetrics_1_0_0, nil
 	case OpenMetricsVersion_2_0_0_rc:
-		// OpenMetrics 2.0.0-rc is experimental and encode-only.
+		// OpenMetrics 2.0.0-rc is experimental.
 		return FmtOpenMetrics_2_0_0_rc, nil
 	case OpenMetricsVersion_2_0_0:
-		// OpenMetrics 2.0.0 is experimental and encode-only.
+		// OpenMetrics 2.0.0 is experimental.
 		return FmtOpenMetrics_2_0_0, nil
 	default:
 		return FmtUnknown, errors.New("unknown open metrics version string")

expfmt/openmetrics_2_0_create.go

@@ -25,14 +25,16 @@ import (
 
 	dto "github.com/prometheus/client_model/go"
 	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"github.com/prometheus/common/model"
 )
 
 // MetricFamilyToOpenMetrics20 converts a MetricFamily proto message into the
 // OpenMetrics text format version 2.0.0 and writes the resulting lines to 'out'.
 // It returns the number of bytes written and any error encountered.
 //
-// NOTE: This method targets OpenMetrics 2.0.0 (currently aligned with 2.0-rc.0) which is experimental and
-// encode-only. All metric types defined in client_model (counter, gauge, summary, untyped, histogram,
+// NOTE: This method targets OpenMetrics 2.0.0 (currently aligned with 2.0-rc.0) which is experimental.
+// All metric types defined in client_model (counter, gauge, summary, untyped, histogram,
 // and gaugehistogram) are supported; info and stateset are not supported as they are not present in
 // client_model. Breaking changes might happen in the future.
 // EncoderOptions are accepted for signature compatibility with
@@ -383,9 +385,6 @@ func writeCompositeSummary(w enhancedWriter, name string, metric *dto.Metric) (i
 	if math.IsNaN(sum) {
 		return 0, fmt.Errorf("summary sum cannot be NaN in metric %s", name)
 	}
-	if sum < 0 {
-		return 0, fmt.Errorf("summary sum cannot be negative (%g) in metric %s", sum, name)
-	}
 
 	var prevQuantile float64
 	for i, q := range s.Quantile {
@@ -403,11 +402,6 @@ func writeCompositeSummary(w enhancedWriter, name string, metric *dto.Metric) (i
 			return 0, fmt.Errorf("summary quantiles must be strictly increasing: %g <= %g in metric %s", qv, prevQuantile, name)
 		}
 		prevQuantile = qv
-
-		v := q.GetValue()
-		if !math.IsNaN(v) && v < 0 {
-			return 0, fmt.Errorf("summary quantile value cannot be negative (%g) in metric %s", v, name)
-		}
 	}
 
 	if s.CreatedTimestamp != nil {
@@ -547,7 +541,10 @@ func writeCompositeHistogram(w enhancedWriter, name string, metric *dto.Metric,
 			}
 			return 0, fmt.Errorf("histogram count cannot be NaN in metric %s", name)
 		}
-		if !isGauge && c < 0 {
+		if c < 0 {
+			if isGauge {
+				return 0, fmt.Errorf("gaugehistogram count cannot be negative (%g) in metric %s", c, name)
+			}
 			return 0, fmt.Errorf("histogram count cannot be negative (%g) in metric %s", c, name)
 		}
 	}
@@ -565,7 +562,7 @@ func writeCompositeHistogram(w enhancedWriter, name string, metric *dto.Metric,
 	}
 
 	if isNative {
-		if err := validateNativeHistogram(name, h, isGauge); err != nil {
+		if err := validateNativeHistogram(name, h); err != nil {
 			return 0, err
 		}
 	}
@@ -709,7 +706,7 @@ func writeCompositeHistogram(w enhancedWriter, name string, metric *dto.Metric,
 	return written, nil
 }
 
-func validateNativeHistogram(name string, h *dto.Histogram, isGauge bool) error {
+func validateNativeHistogram(name string, h *dto.Histogram) error {
 	schema := *h.Schema
 	if schema < -4 || schema > 8 {
 		return fmt.Errorf("native histogram schema %d is out of range [-4, 8] in metric %s", schema, name)
@@ -725,15 +722,15 @@ func validateNativeHistogram(name string, h *dto.Histogram, isGauge bool) error
 		if math.IsNaN(c) {
 			return fmt.Errorf("native histogram zero_count cannot be NaN in metric %s", name)
 		}
-		if !isGauge && c < 0 {
+		if c < 0 {
 			return fmt.Errorf("native histogram zero_count cannot be negative (%g) in metric %s", c, name)
 		}
 	}
 
-	if err := validateSpansAndBuckets(name, "negative", h.NegativeSpan, h.NegativeDelta, h.NegativeCount, isGauge); err != nil {
+	if err := validateSpansAndBuckets(name, "negative", h.NegativeSpan, h.NegativeDelta, h.NegativeCount); err != nil {
 		return err
 	}
-	return validateSpansAndBuckets(name, "positive", h.PositiveSpan, h.PositiveDelta, h.PositiveCount, isGauge)
+	return validateSpansAndBuckets(name, "positive", h.PositiveSpan, h.PositiveDelta, h.PositiveCount)
 }
 
 func validateSpansAndBuckets(
@@ -742,7 +739,6 @@ func validateSpansAndBuckets(
 	spans []*dto.BucketSpan,
 	deltas []int64,
 	floatCounts []float64,
-	isGauge bool,
 ) error {
 	isFloatBuckets := len(floatCounts) > 0
 	var numBuckets int
@@ -779,15 +775,15 @@ func validateSpansAndBuckets(
 			if math.IsNaN(v) {
 				return fmt.Errorf("%s bucket count cannot be NaN in metric %s", spanName, name)
 			}
-			if !isGauge && v < 0 {
+			if v < 0 {
 				return fmt.Errorf("%s bucket count cannot be negative (%g) in metric %s", spanName, v, name)
 			}
 		}
 	} else {
 		var current int64
 		for _, d := range deltas {
 			current += d
-			if !isGauge && current < 0 {
+			if current < 0 {
 				return fmt.Errorf("%s bucket count cannot be negative (%d) in metric %s", spanName, current, name)
 			}
 		}
@@ -996,7 +992,7 @@ func validateClassicBuckets(
 			if math.IsNaN(c) {
 				return fmt.Errorf("classic bucket count cannot be NaN in metric %s", name)
 			}
-			if !isGauge && c < 0 {
+			if c < 0 {
 				return fmt.Errorf("classic bucket count cannot be negative (%g) in metric %s", c, name)
 			}
 		}
@@ -1009,7 +1005,7 @@ func validateClassicBuckets(
 			bCount = float64(*b.CumulativeCount)
 		}
 
-		if !isGauge && i > 0 && bCount < prevCount {
+		if i > 0 && bCount < prevCount {
 			return fmt.Errorf("classic bucket counts must be monotonically increasing: %g < %g in metric %s", bCount, prevCount, name)
 		}
 		prevCount = bCount
@@ -1037,7 +1033,7 @@ func validateClassicBuckets(
 		}
 	}
 
-	if !infSeen && len(h.Bucket) > 0 && !isGauge {
+	if !infSeen && len(h.Bucket) > 0 {
 		if sampleCount < prevCount {
 			return fmt.Errorf("sample count (%g) is less than highest bucket count (%g) in metric %s", sampleCount, prevCount, name)
 		}
@@ -1142,6 +1138,9 @@ func validateLabels20(labels []*dto.LabelPair) error {
 		if lname == "" {
 			return errors.New("label name cannot be empty")
 		}
+		if lname == string(model.MetricNameLabel) {
+			return fmt.Errorf("label name %q is reserved", model.MetricNameLabel)
+		}
 		if containsRawNewline(lname) {
 			return fmt.Errorf("label name %q contains raw newlines", lname)
 		}