[exporter/prometheusremotewrite] Fix: Don't drop batch in case of fai…

…lure to translate metrics (#29729)

Don't drop a whole batch in case of failure to
translate from Otel to Prometheus. Instead, with this PR we are trying
to send to Prometheus all the metrics that were properly translated and
create a warning message for failures to translate.

This PR also adds supports to telemetry in this component so that it is
possible to inspect how the translation process is happening and
identify failed translations.

I opted to not include the number of time series that failed translation
because I don't want to make assumptions about how the `FromMetrics`
function works. Instead we are just publishing if there was any failure
during the translation process and the number of time series returned.

**Link to tracking Issue:** #15281

**Testing:** UTs were added to account for the case that you have mixed
metrics, with some succeeding the translation and some failing.

---------

Signed-off-by: Raphael Silva <rapphil@gmail.com>
Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>
Co-authored-by: bryan-aguilar <46550959+bryan-aguilar@users.noreply.github.com>
Co-authored-by: Bryan Aguilar <bryaag@amazon.com>

.chloggen/prw_failure_translate.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: prometheusremotewriteexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Publish telemetry about translation of metrics from Otel to Prometheus. Don't drop all data points if some fail translation.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [29729]
+
+# (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:
+
+# 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: [user]

exporter/prometheusremotewriteexporter/exporter.go

@@ -25,12 +25,35 @@ import (
 	"go.opentelemetry.io/collector/consumer/consumererror"
 	"go.opentelemetry.io/collector/exporter"
 	"go.opentelemetry.io/collector/pdata/pmetric"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
 	"go.uber.org/multierr"
+	"go.uber.org/zap"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/exporter/prometheusremotewriteexporter/internal/metadata"
 	prometheustranslator "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheusremotewrite"
 )
 
+type prwTelemetry interface {
+	recordTranslationFailure(ctx context.Context)
+	recordTranslatedTimeSeries(ctx context.Context, numTS int)
+}
+
+type prwTelemetryOtel struct {
+	failedTranslations   metric.Int64Counter
+	translatedTimeSeries metric.Int64Counter
+	otelAttrs            []attribute.KeyValue
+}
+
+func (p *prwTelemetryOtel) recordTranslationFailure(ctx context.Context) {
+	p.failedTranslations.Add(ctx, 1, metric.WithAttributes(p.otelAttrs...))
+}
+
+func (p *prwTelemetryOtel) recordTranslatedTimeSeries(ctx context.Context, numTS int) {
+	p.translatedTimeSeries.Add(ctx, int64(numTS), metric.WithAttributes(p.otelAttrs...))
+}
+
 // prwExporter converts OTLP metrics to Prometheus remote write TimeSeries and sends them to a remote endpoint.
 type prwExporter struct {
 	endpointURL       *url.URL
@@ -45,6 +68,31 @@ type prwExporter struct {
 	retrySettings     configretry.BackOffConfig
 	wal               *prweWAL
 	exporterSettings  prometheusremotewrite.Settings
+	telemetry         prwTelemetry
+}
+
+func newPRWTelemetry(set exporter.CreateSettings) (prwTelemetry, error) {
+
+	meter := metadata.Meter(set.TelemetrySettings)
+	// TODO: create helper functions similar to the processor helper: BuildCustomMetricName
+	prefix := "exporter/" + metadata.Type.String() + "/"
+	failedTranslations, errFailedTranslation := meter.Int64Counter(prefix+"failed_translations",
+		metric.WithDescription("Number of translation operations that failed to translate metrics from Otel to Prometheus"),
+		metric.WithUnit("1"),
+	)
+
+	translatedTimeSeries, errTranslatedMetrics := meter.Int64Counter(prefix+"translated_time_series",
+		metric.WithDescription("Number of Prometheus time series that were translated from OTel metrics"),
+		metric.WithUnit("1"),
+	)
+
+	return &prwTelemetryOtel{
+		failedTranslations:   failedTranslations,
+		translatedTimeSeries: translatedTimeSeries,
+		otelAttrs: []attribute.KeyValue{
+			attribute.String("exporter", set.ID.String()),
+		},
+	}, errors.Join(errFailedTranslation, errTranslatedMetrics)
 }
 
 // newPRWExporter initializes a new prwExporter instance and sets fields accordingly.
@@ -59,6 +107,11 @@ func newPRWExporter(cfg *Config, set exporter.CreateSettings) (*prwExporter, err
 		return nil, errors.New("invalid endpoint")
 	}
 
+	prwTelemetry, err := newPRWTelemetry(set)
+	if err != nil {
+		return nil, err
+	}
+
 	userAgentHeader := fmt.Sprintf("%s/%s", strings.ReplaceAll(strings.ToLower(set.BuildInfo.Description), " ", "-"), set.BuildInfo.Version)
 
 	prwe := &prwExporter{
@@ -79,6 +132,7 @@ func newPRWExporter(cfg *Config, set exporter.CreateSettings) (*prwExporter, err
 			AddMetricSuffixes:   cfg.AddMetricSuffixes,
 			SendMetadata:        cfg.SendMetadata,
 		},
+		telemetry: prwTelemetry,
 	}
 
 	prwe.wal = newWAL(cfg.WAL, prwe.export)
@@ -128,15 +182,19 @@ func (prwe *prwExporter) PushMetrics(ctx context.Context, md pmetric.Metrics) er
 
 		tsMap, err := prometheusremotewrite.FromMetrics(md, prwe.exporterSettings)
 		if err != nil {
-			err = consumererror.NewPermanent(err)
+			prwe.telemetry.recordTranslationFailure(ctx)
+			prwe.settings.Logger.Debug("failed to translate metrics, exporting remaining metrics", zap.Error(err), zap.Int("translated", len(tsMap)))
 		}
 
+		prwe.telemetry.recordTranslatedTimeSeries(ctx, len(tsMap))
+
 		var m []*prompb.MetricMetadata
 		if prwe.exporterSettings.SendMetadata {
 			m = prometheusremotewrite.OtelMetricsToMetadata(md, prwe.exporterSettings.AddMetricSuffixes)
 		}
+
 		// Call export even if a conversion error, since there may be points that were successfully converted.
-		return multierr.Combine(err, prwe.handleExport(ctx, tsMap, m))
+		return prwe.handleExport(ctx, tsMap, m)
 	}
 }
 

exporter/prometheusremotewriteexporter/exporter_test.go

@@ -372,6 +372,19 @@ func runExportPipeline(ts *prompb.TimeSeries, endpoint *url.URL) error {
 	return prwe.handleExport(context.Background(), testmap, nil)
 }
 
+type mockPRWTelemetry struct {
+	failedTranslations   int
+	translatedTimeSeries int
+}
+
+func (m *mockPRWTelemetry) recordTranslationFailure(_ context.Context) {
+	m.failedTranslations++
+}
+
+func (m *mockPRWTelemetry) recordTranslatedTimeSeries(_ context.Context, numTs int) {
+	m.translatedTimeSeries += numTs
+}
+
 // Test_PushMetrics checks the number of TimeSeries received by server and the number of metrics dropped is the same as
 // expected
 func Test_PushMetrics(t *testing.T) {
@@ -420,6 +433,11 @@ func Test_PushMetrics(t *testing.T) {
 
 	emptySummaryBatch := getMetricsFromMetricList(invalidMetrics[emptySummary])
 
+	// partial success (or partial failure) cases
+
+	partialSuccess1 := getMetricsFromMetricList(validMetrics1[validSum], validMetrics2[validSum],
+		validMetrics1[validIntGauge], validMetrics2[validIntGauge], invalidMetrics[emptyGauge])
+
 	// staleNaN cases
 	staleNaNHistogramBatch := getMetricsFromMetricList(staleNaNMetrics[staleNaNHistogram])
 	staleNaNEmptyHistogramBatch := getMetricsFromMetricList(staleNaNMetrics[staleNaNEmptyHistogram])
@@ -457,20 +475,23 @@ func Test_PushMetrics(t *testing.T) {
 	}
 
 	tests := []struct {
-		name               string
-		metrics            pmetric.Metrics
-		reqTestFunc        func(t *testing.T, r *http.Request, expected int, isStaleMarker bool)
-		expectedTimeSeries int
-		httpResponseCode   int
-		returnErr          bool
-		isStaleMarker      bool
-		skipForWAL         bool
+		name                       string
+		metrics                    pmetric.Metrics
+		reqTestFunc                func(t *testing.T, r *http.Request, expected int, isStaleMarker bool)
+		expectedTimeSeries         int
+		httpResponseCode           int
+		returnErr                  bool
+		isStaleMarker              bool
+		skipForWAL                 bool
+		expectedFailedTranslations int
 	}{
 		{
-			name:             "invalid_type_case",
-			metrics:          invalidTypeBatch,
-			httpResponseCode: http.StatusAccepted,
-			returnErr:        true,
+			name:                       "invalid_type_case",
+			metrics:                    invalidTypeBatch,
+			httpResponseCode:           http.StatusAccepted,
+			reqTestFunc:                checkFunc,
+			expectedTimeSeries:         1, // the resource target metric.
+			expectedFailedTranslations: 1,
 		},
 		{
 			name:               "intSum_case",
@@ -567,32 +588,40 @@ func Test_PushMetrics(t *testing.T) {
 			skipForWAL: true,
 		},
 		{
-			name:             "emptyGauge_case",
-			metrics:          emptyDoubleGaugeBatch,
-			reqTestFunc:      checkFunc,
-			httpResponseCode: http.StatusAccepted,
-			returnErr:        true,
+			name:                       "emptyGauge_case",
+			metrics:                    emptyDoubleGaugeBatch,
+			reqTestFunc:                checkFunc,
+			httpResponseCode:           http.StatusAccepted,
+			expectedFailedTranslations: 1,
+		},
+		{
+			name:                       "emptyCumulativeSum_case",
+			metrics:                    emptyCumulativeSumBatch,
+			reqTestFunc:                checkFunc,
+			httpResponseCode:           http.StatusAccepted,
+			expectedFailedTranslations: 1,
 		},
 		{
-			name:             "emptyCumulativeSum_case",
-			metrics:          emptyCumulativeSumBatch,
-			reqTestFunc:      checkFunc,
-			httpResponseCode: http.StatusAccepted,
-			returnErr:        true,
+			name:                       "emptyCumulativeHistogram_case",
+			metrics:                    emptyCumulativeHistogramBatch,
+			reqTestFunc:                checkFunc,
+			httpResponseCode:           http.StatusAccepted,
+			expectedFailedTranslations: 1,
 		},
 		{
-			name:             "emptyCumulativeHistogram_case",
-			metrics:          emptyCumulativeHistogramBatch,
-			reqTestFunc:      checkFunc,
-			httpResponseCode: http.StatusAccepted,
-			returnErr:        true,
+			name:                       "emptySummary_case",
+			metrics:                    emptySummaryBatch,
+			reqTestFunc:                checkFunc,
+			httpResponseCode:           http.StatusAccepted,
+			expectedFailedTranslations: 1,
 		},
 		{
-			name:             "emptySummary_case",
-			metrics:          emptySummaryBatch,
-			reqTestFunc:      checkFunc,
-			httpResponseCode: http.StatusAccepted,
-			returnErr:        true,
+			name:                       "partialSuccess_case",
+			metrics:                    partialSuccess1,
+			reqTestFunc:                checkFunc,
+			httpResponseCode:           http.StatusAccepted,
+			expectedTimeSeries:         4,
+			expectedFailedTranslations: 1,
 		},
 		{
 			name:               "staleNaNIntGauge_case",
@@ -668,6 +697,7 @@ func Test_PushMetrics(t *testing.T) {
 				}
 				t.Run(tt.name, func(t *testing.T) {
 					t.Parallel()
+					mockTelemetry := &mockPRWTelemetry{}
 					server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 						if tt.reqTestFunc != nil {
 							tt.reqTestFunc(t, r, tt.expectedTimeSeries, tt.isStaleMarker)
@@ -716,7 +746,10 @@ func Test_PushMetrics(t *testing.T) {
 					}
 					set := exportertest.NewNopCreateSettings()
 					set.BuildInfo = buildInfo
+
 					prwe, nErr := newPRWExporter(cfg, set)
+					prwe.telemetry = mockTelemetry
+
 					require.NoError(t, nErr)
 					ctx, cancel := context.WithCancel(context.Background())
 					defer cancel()
@@ -729,6 +762,9 @@ func Test_PushMetrics(t *testing.T) {
 						assert.Error(t, err)
 						return
 					}
+
+					assert.Equal(t, tt.expectedFailedTranslations, mockTelemetry.failedTranslations)
+					assert.Equal(t, tt.expectedTimeSeries, mockTelemetry.translatedTimeSeries)
 					assert.NoError(t, err)
 				})
 			}

exporter/prometheusremotewriteexporter/go.mod

@@ -23,6 +23,7 @@ require (
 	go.opentelemetry.io/collector/consumer v0.96.1-0.20240306115632-b2693620eff6
 	go.opentelemetry.io/collector/exporter v0.96.1-0.20240306115632-b2693620eff6
 	go.opentelemetry.io/collector/pdata v1.3.1-0.20240306115632-b2693620eff6
+	go.opentelemetry.io/otel v1.24.0
 	go.opentelemetry.io/otel/metric v1.24.0
 	go.opentelemetry.io/otel/trace v1.24.0
 	go.uber.org/goleak v1.3.0
@@ -70,7 +71,6 @@ require (
 	go.opentelemetry.io/collector/receiver v0.96.1-0.20240306115632-b2693620eff6 // indirect
 	go.opentelemetry.io/collector/semconv v0.96.1-0.20240306115632-b2693620eff6 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.49.0 // indirect
-	go.opentelemetry.io/otel v1.24.0 // indirect
 	go.opentelemetry.io/otel/exporters/prometheus v0.46.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.24.0 // indirect
 	go.opentelemetry.io/otel/sdk/metric v1.24.0 // indirect