Return first validation error on sample ingestion

CHANGELOG.md

@@ -97,6 +97,7 @@
 * [ENHANCEMENT] Output all config fields to /config API, including those with empty value. #2209
 * [ENHANCEMENT] Add "missing_metric_name" and "metric_name_invalid" reasons to cortex_discarded_samples_total metric. #2346
 * [ENHANCEMENT] Experimental TSDB: sample ingestion errors are now reported via existing `cortex_discarded_samples_total` metric. #2370
+* [ENHANCEMENT] Failures on samples at distributors and ingesters return the first validation error as opposed to the last. #XXXX 
 * [BUGFIX] Ensure user state metrics are updated if a transfer fails. #2338
 * [BUGFIX] Fixed etcd client keepalive settings. #2278
 * [BUGFIX] Fixed bug in updating last element of FIFO cache. #2270

pkg/distributor/distributor.go

@@ -329,7 +329,7 @@ func (d *Distributor) Push(ctx context.Context, req *client.WriteRequest) (*clie
 		return nil, err
 	}
 
-	var lastPartialErr error
+	var firstPartialErr error
 	removeReplica := false
 
 	numSamples := 0
@@ -398,8 +398,8 @@ func (d *Distributor) Push(ctx context.Context, req *client.WriteRequest) (*clie
 
 		// Errors in validation are considered non-fatal, as one series in a request may contain
 		// invalid data but all the remaining series could be perfectly valid.
-		if err != nil {
-			lastPartialErr = err
+		if err != nil && firstPartialErr == nil {
+			firstPartialErr = err
 		}
 
 		// validateSeries would have returned an emptyPreallocSeries if there were no valid samples.
@@ -417,7 +417,7 @@ func (d *Distributor) Push(ctx context.Context, req *client.WriteRequest) (*clie
 		// Ensure the request slice is reused if there's no series passing the validation.
 		client.ReuseSlice(req.Timeseries)
 
-		return &client.WriteResponse{}, lastPartialErr
+		return &client.WriteResponse{}, firstPartialErr
 	}
 
 	now := time.Now()
@@ -461,7 +461,7 @@ func (d *Distributor) Push(ctx context.Context, req *client.WriteRequest) (*clie
 	if err != nil {
 		return nil, err
 	}
-	return &client.WriteResponse{}, lastPartialErr
+	return &client.WriteResponse{}, firstPartialErr
 }
 
 func sortLabelsIfNeeded(labels []client.LabelAdapter) {

pkg/distributor/distributor_test.go

@@ -1139,6 +1139,18 @@ func TestDistributorValidation(t *testing.T) {
 			}},
 			err: httpgrpc.Errorf(http.StatusBadRequest, `sample for 'testmetric{foo2="bar2", foo="bar"}' has 3 label names; limit 2`),
 		},
+		// Test multiple validation fails return the first one.
+		{
+			labels: []labels.Labels{
+				{{Name: labels.MetricName, Value: "testmetric"}, {Name: "foo", Value: "bar"}, {Name: "foo2", Value: "bar2"}},
+				{{Name: labels.MetricName, Value: "testmetric"}, {Name: "foo", Value: "bar"}},
+			},
+			samples: []client.Sample{
+				{TimestampMs: int64(now), Value: 2},
+				{TimestampMs: int64(past), Value: 2},
+			},
+			err: httpgrpc.Errorf(http.StatusBadRequest, `sample for 'testmetric{foo2="bar2", foo="bar"}' has 3 label names; limit 2`),
+		},
 	} {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
 			var limits validation.Limits

pkg/ingester/ingester.go

@@ -357,7 +357,7 @@ func (i *Ingester) Push(ctx context.Context, req *client.WriteRequest) (*client.
 		return nil, fmt.Errorf("no user id")
 	}
 
-	var lastPartialErr *validationError
+	var firstPartialErr *validationError
 	var record *Record
 	if i.cfg.WALConfig.WALEnabled {
 		record = recordPool.Get().(*Record)
@@ -382,7 +382,9 @@ func (i *Ingester) Push(ctx context.Context, req *client.WriteRequest) (*client.
 
 			i.metrics.ingestedSamplesFail.Inc()
 			if ve, ok := err.(*validationError); ok {
-				lastPartialErr = ve
+				if firstPartialErr == nil {
+					firstPartialErr = ve
+				}
 				continue
 			}
 
@@ -391,9 +393,9 @@ func (i *Ingester) Push(ctx context.Context, req *client.WriteRequest) (*client.
 		}
 	}
 
-	if lastPartialErr != nil {
+	if firstPartialErr != nil {
 		// grpcForwardableError turns the error into a string so it no longer references `req`
-		return &client.WriteResponse{}, grpcForwardableError(userID, lastPartialErr.code, lastPartialErr)
+		return &client.WriteResponse{}, grpcForwardableError(userID, firstPartialErr.code, firstPartialErr)
 	}
 
 	if record != nil {

pkg/ingester/ingester_test.go

@@ -476,6 +476,42 @@ func TestIngesterMetricSeriesLimitExceeded(t *testing.T) {
 	assert.Equal(t, expected, res)
 }
 
+func TestIngesterValidation(t *testing.T) {
+	_, ing := newDefaultTestStore(t)
+	defer services.StopAndAwaitTerminated(context.Background(), ing) //nolint:errcheck
+	userID := "1"
+	ctx := user.InjectOrgID(context.Background(), userID)
+	m := labelPairs{{Name: labels.MetricName, Value: "testmetric"}}
+
+	// As a setup, let's append samples.
+	ing.append(context.Background(), userID, m, 1, 0, client.API, nil)
+
+	for _, tc := range []struct {
+		desc    string
+		lbls    []labels.Labels
+		samples []client.Sample
+		err     error
+	}{
+		{
+			desc: "With multiple append failures, only return the first error.",
+			lbls: []labels.Labels{
+				{{Name: labels.MetricName, Value: "testmetric"}},
+				{{Name: labels.MetricName, Value: "testmetric"}},
+			},
+			samples: []client.Sample{
+				{TimestampMs: 0, Value: 0}, // earlier timestamp, out of order.
+				{TimestampMs: 1, Value: 2}, // same timestamp different value.
+			},
+			err: httpgrpc.Errorf(http.StatusBadRequest, `user=1: sample timestamp out of order; last timestamp: 0.001, incoming timestamp: 0 for series {__name__="testmetric"}`),
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			_, err := ing.Push(ctx, client.ToWriteRequest(tc.lbls, tc.samples, client.API))
+			require.Equal(t, tc.err, err)
+		})
+	}
+}
+
 func BenchmarkIngesterSeriesCreationLocking(b *testing.B) {
 	for i := 1; i <= 32; i++ {
 		b.Run(strconv.Itoa(i), func(b *testing.B) {