feat: Ignore empty streams in distributor if all entries fail validation (#13674)

pkg/distributor/distributor.go

@@ -438,6 +438,10 @@ func (d *Distributor) Push(ctx context.Context, req *logproto.PushRequest) (*log
 				pushSize += len(entry.Line)
 			}
 			stream.Entries = stream.Entries[:n]
+			if len(stream.Entries) == 0 {
+				// Empty stream after validating all the entries
+				continue
+			}
 
 			shardStreamsCfg := d.validator.Limits.ShardStreams(tenantID)
 			if shardStreamsCfg.Enabled {

pkg/distributor/distributor_test.go

@@ -589,6 +589,26 @@ func Test_TruncateLogLines(t *testing.T) {
 	})
 }
 
+func Test_DiscardEmptyStreamsAfterValidation(t *testing.T) {
+	setup := func() (*validation.Limits, *mockIngester) {
+		limits := &validation.Limits{}
+		flagext.DefaultValues(limits)
+
+		limits.MaxLineSize = 5
+		return limits, &mockIngester{}
+	}
+
+	t.Run("it discards invalid entries and discards resulting empty streams completely", func(t *testing.T) {
+		limits, ingester := setup()
+		distributors, _ := prepare(t, 1, 5, limits, func(addr string) (ring_client.PoolClient, error) { return ingester, nil })
+
+		_, err := distributors[0].Push(ctx, makeWriteRequest(1, 10))
+		require.Equal(t, err, httpgrpc.Errorf(http.StatusBadRequest, fmt.Sprintf(validation.LineTooLongErrorMsg, 5, "{foo=\"bar\", service_name=\"unknown_service\"}", 10)))
+		topVal := ingester.Peek()
+		require.Nil(t, topVal)
+	})
+}
+
 func TestStreamShard(t *testing.T) {
 	// setup base stream.
 	baseStream := logproto.Stream{}