[receiver/prometheusremotewrite] Parse labels into resource and scope attributes

When translating Prometheus metrics to OTLP, we rely on the metric called 'target_info' that may come in different remote write requests.
The target_info metric is used to populate resource attributes of different OTel metrics.
Currently, we're not doing supporting the correct usage of 'target_info'.

Signed-off-by: Arthur Silva Sens <[email protected]>

Author: ArthurSens

.chloggen/prwreceiver-parselabels.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: receiver/prometheusremotewrite
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Parse labels from Prometheus Remote Write requests into Resource and Scope Attributes
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35656]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Warning - The HTTP Server still doesn't pass metrics to the next consumer. The component is unusable for now.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api, user]

receiver/prometheusremotewritereceiver/go.mod

@@ -5,6 +5,7 @@ go 1.22.0
 require (
 	github.com/gogo/protobuf v1.3.2
 	github.com/golang/snappy v0.0.4
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest v0.111.0
 	github.com/prometheus/prometheus v0.54.1
 	github.com/stretchr/testify v1.9.0
 	go.opentelemetry.io/collector/component v0.112.0
@@ -54,6 +55,7 @@ require (
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.111.0 // indirect
 	github.com/pierrec/lz4/v4 v4.1.21 // indirect
 	github.com/pkg/browser v0.0.0-20240102092130-5ac0b6a4141c // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
@@ -77,7 +79,7 @@ require (
 	go.opentelemetry.io/collector/pdata/pprofile v0.112.0 // indirect
 	go.opentelemetry.io/collector/pipeline v0.112.0 // indirect
 	go.opentelemetry.io/collector/receiver/receiverprofiles v0.112.0 // indirect
-	go.opentelemetry.io/collector/semconv v0.105.0 // indirect
+	go.opentelemetry.io/collector/semconv v0.112.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.56.0 // indirect
 	go.opentelemetry.io/otel v1.31.0 // indirect
 	go.opentelemetry.io/otel/metric v1.31.0 // indirect

receiver/prometheusremotewritereceiver/go.sum

@@ -14,11 +14,13 @@ import (
 
 	"github.com/gogo/protobuf/proto"
 	promconfig "github.com/prometheus/prometheus/config"
+	"github.com/prometheus/prometheus/model/labels"
 	writev2 "github.com/prometheus/prometheus/prompb/io/prometheus/write/v2"
 	promremote "github.com/prometheus/prometheus/storage/remote"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/component/componentstatus"
 	"go.opentelemetry.io/collector/consumer"
+	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.opentelemetry.io/collector/receiver"
 	"go.uber.org/zap/zapcore"
@@ -28,6 +30,7 @@ func newRemoteWriteReceiver(settings receiver.Settings, cfg *Config, nextConsume
 	return &prometheusRemoteWriteReceiver{
 		settings:     settings,
 		nextConsumer: nextConsumer,
+		jobInstanceCache: make(map[string]pmetric.ResourceMetrics),
 		config:       cfg,
 		server: &http.Server{
 			ReadTimeout: 60 * time.Second,
@@ -39,6 +42,8 @@ type prometheusRemoteWriteReceiver struct {
 	settings     receiver.Settings
 	nextConsumer consumer.Metrics
 
+	jobInstanceCache map[string]pmetric.ResourceMetrics
+
 	config *Config
 	server *http.Server
 }
@@ -150,8 +155,71 @@ func (prw *prometheusRemoteWriteReceiver) parseProto(contentType string) (promco
 }
 
 // translateV2 translates a v2 remote-write request into OTLP metrics.
-// For now translateV2 is not implemented and returns an empty metrics.
+// translate is not feature complete.
 // nolint
-func (prw *prometheusRemoteWriteReceiver) translateV2(_ context.Context, _ *writev2.Request) (pmetric.Metrics, promremote.WriteResponseStats, error) {
-	return pmetric.NewMetrics(), promremote.WriteResponseStats{}, nil
+func (prw *prometheusRemoteWriteReceiver) translateV2(_ context.Context, req *writev2.Request) (pmetric.Metrics, promremote.WriteResponseStats, error) {
+	var (
+		badRequestErrors []error
+		otelMetrics      = pmetric.NewMetrics()
+		b                = labels.NewScratchBuilder(0)
+		stats            = promremote.WriteResponseStats{}
+	)
+
+
+	for _, ts := range req.Timeseries {
+		ls := ts.ToLabels(&b, req.Symbols)
+
+		if !ls.Has(labels.MetricName) {
+			badRequestErrors = append(badRequestErrors, fmt.Errorf("missing metric name in labels"))
+			continue
+		} else if duplicateLabel, hasDuplicate := ls.HasDuplicateLabelNames(); hasDuplicate {
+			badRequestErrors = append(badRequestErrors, fmt.Errorf("duplicate label %q in labels", duplicateLabel))
+			continue
+		}
+
+		var rm pmetric.ResourceMetrics
+		// This cache should be populated by the metric 'target_info', but we're not handling it yet.
+		cacheEntry, ok := prw.jobInstanceCache[ls.Get("instance")+ls.Get("job")]
+		if ok {
+			rm = pmetric.NewResourceMetrics()
+			cacheEntry.CopyTo(rm)
+		} else {
+			// A remote-write request can have multiple timeseries with the same instance and job labels.
+			// While they are different timeseries in Prometheus, we're handling it as the same OTLP metric
+			// until we support 'target_info'.
+			rm = otelMetrics.ResourceMetrics().AppendEmpty()
+			parseJobAndInstance(rm.Resource().Attributes(), ls.Get("instance"), ls.Get("job"))
+			prw.jobInstanceCache[ls.Get("instance")+ls.Get("job")] = rm
+
+
+			scopeAttributes := rm.ScopeMetrics().AppendEmpty().Scope().Attributes()
+			for _, l := range ls {
+				if l.Name == "instance" || l.Name == "job" || l.Name == labels.MetricName {
+					continue
+				}
+				scopeAttributes.PutStr(l.Name, l.Value)
+			}
+		}
+
+		// Next step is to process metadata and samples.
+	}
+
+	return otelMetrics, stats, errors.Join(badRequestErrors...)
+}
+
+// parseJobAndInstance turns the job and instance labels service resource attributes.
+// Following the specification at https://opentelemetry.io/docs/specs/otel/compatibility/prometheus_and_openmetrics/
+func parseJobAndInstance(dest pcommon.Map, instance, job string) {
+	if job != "" {
+		dest.PutStr("service.namespace", job)
+	}
+	if instance != "" {
+		parts := strings.Split(instance, "/")
+		if len(parts) == 2 {
+			dest.PutStr("service.name", parts[0])
+			dest.PutStr("service.instance.id", parts[1])
+			return
+		}
+		dest.PutStr("service.name", instance)
+	}
 }

receiver/prometheusremotewritereceiver/receiver.go

@@ -14,13 +14,37 @@ import (
 	"github.com/golang/snappy"
 	promconfig "github.com/prometheus/prometheus/config"
 	writev2 "github.com/prometheus/prometheus/prompb/io/prometheus/write/v2"
+	"github.com/prometheus/prometheus/storage/remote"
 	"github.com/stretchr/testify/assert"
 	"go.opentelemetry.io/collector/component/componenttest"
 	"go.opentelemetry.io/collector/consumer/consumertest"
+	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.opentelemetry.io/collector/receiver/receivertest"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatatest/pmetrictest"
 )
 
-func setupServer(t *testing.T) {
+var (
+	writeV2RequestFixture = &writev2.Request{
+		Symbols: []string{"", "__name__", "test_metric1", "job", "test", "instance", "service-x/107cn001", "d", "e", "foo", "bar", "f", "g", "h", "i", "Test gauge for test purposes", "Maybe op/sec who knows (:", "Test counter for test purposes"},
+		Timeseries: []writev2.TimeSeries{
+			{
+				LabelsRefs: []uint32{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, // Symbolized writeRequestFixture.Timeseries[0].Labels
+				Samples:    []writev2.Sample{{Value: 1, Timestamp: 1}},
+			},
+			{
+				LabelsRefs: []uint32{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, // Same series as first. Should use the same resource metrics.
+				Samples:    []writev2.Sample{{Value: 2, Timestamp: 2}},
+			},
+			{
+				LabelsRefs: []uint32{1, 2, 3, 9, 5, 10, 7, 8, 9, 10}, // This series has different label values for job and instance.
+				Samples:    []writev2.Sample{{Value: 2, Timestamp: 2}},
+			},
+		},
+	}
+)
+
+func setupMetricsReceiver(t *testing.T) *prometheusRemoteWriteReceiver {
 	t.Helper()
 
 	factory := NewFactory()
@@ -30,6 +54,13 @@ func setupServer(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NotNil(t, prwReceiver, "metrics receiver creation failed")
 
+	return prwReceiver.(*prometheusRemoteWriteReceiver)
+}
+
+func setupServer(t *testing.T) {
+	t.Helper()
+
+	prwReceiver := setupMetricsReceiver(t)
 	ctx, cancel := context.WithCancel(context.Background())
 	t.Cleanup(cancel)
 
@@ -98,3 +129,82 @@ func TestHandlePRWContentTypeNegotiation(t *testing.T) {
 		})
 	}
 }
+
+func TestTranslateV2(t *testing.T) {
+	prwReceiver := setupMetricsReceiver(t)
+	ctx, cancel := context.WithCancel(context.Background())
+	t.Cleanup(cancel)
+
+	for _, tc := range []struct {
+		name            string
+		request         *writev2.Request
+		expectError     string
+		expectedMetrics pmetric.Metrics
+		expectedStats   remote.WriteResponseStats
+	}{
+		{
+			name: "missing metric name",
+			request: &writev2.Request{
+				Symbols: []string{"", "foo", "bar"},
+				Timeseries: []writev2.TimeSeries{
+					{
+						LabelsRefs: []uint32{1, 2},
+						Samples:    []writev2.Sample{{Value: 1, Timestamp: 1}},
+					},
+				},
+			},
+			expectError: "missing metric name in labels",
+		},
+		{
+			name: "duplicate label",
+			request: &writev2.Request{
+				Symbols: []string{"", "__name__", "test"},
+				Timeseries: []writev2.TimeSeries{
+					{
+						LabelsRefs: []uint32{1, 2, 1, 2},
+						Samples:    []writev2.Sample{{Value: 1, Timestamp: 1}},
+					},
+				},
+			},
+			expectError: `duplicate label "__name__" in labels`,
+		},
+		{
+			name:    "valid request",
+			request: writeV2RequestFixture,
+			expectedMetrics: func() pmetric.Metrics {
+				expected := pmetric.NewMetrics()
+				rm1 := expected.ResourceMetrics().AppendEmpty()
+				rmAttributes1 := rm1.Resource().Attributes()
+				rmAttributes1.PutStr("service.namespace", "test")
+				rmAttributes1.PutStr("service.name", "service-x")
+				rmAttributes1.PutStr("service.instance.id", "107cn001")
+				smAttributes1 := rm1.ScopeMetrics().AppendEmpty().Scope().Attributes()
+				smAttributes1.PutStr("d", "e")
+				smAttributes1.PutStr("foo", "bar")
+
+				rm2 := expected.ResourceMetrics().AppendEmpty()
+				rmAttributes2 := rm2.Resource().Attributes()
+				rmAttributes2.PutStr("service.namespace", "foo")
+				rmAttributes2.PutStr("service.name", "bar")
+				smAttributes2 := rm2.ScopeMetrics().AppendEmpty().Scope().Attributes()
+				smAttributes2.PutStr("d", "e")
+				smAttributes2.PutStr("foo", "bar")
+
+				return expected
+			}(),
+			expectedStats: remote.WriteResponseStats{},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			metrics, stats, err := prwReceiver.translateV2(ctx, tc.request)
+			if tc.expectError != "" {
+				assert.ErrorContains(t, err, tc.expectError)
+				return
+			}
+
+			assert.NoError(t, err)
+			assert.NoError(t, pmetrictest.CompareMetrics(tc.expectedMetrics, metrics))
+			assert.Equal(t, tc.expectedStats, stats)
+		})
+	}
+}