Use enum for EngineType in GRPC

GRPC is used for communication between thanos components and
defaultEngine was a string before. Enum makes more sense, and
hence the request.Enigne type has been changed to
querypb.EngineType.
Default case is handled with another default value provided in
the enum.

Signed-off-by: Pradyumna Krishna <git@onpy.in>

cmd/thanos/query.go

@@ -30,6 +30,7 @@ import (
 	"github.com/thanos-community/promql-engine/api"
 
 	apiv1 "github.com/thanos-io/thanos/pkg/api/query"
+	"github.com/thanos-io/thanos/pkg/api/query/querypb"
 	"github.com/thanos-io/thanos/pkg/compact/downsample"
 	"github.com/thanos-io/thanos/pkg/component"
 	"github.com/thanos-io/thanos/pkg/discovery/cache"
@@ -333,7 +334,7 @@ func registerQuery(app *extkingpin.App) {
 			*queryTelemetryDurationQuantiles,
 			*queryTelemetrySamplesQuantiles,
 			*queryTelemetrySeriesQuantiles,
-			apiv1.PromqlEngineType(*defaultEngine),
+			*defaultEngine,
 			storeRateLimits,
 			queryMode(*promqlQueryMode),
 		)
@@ -409,7 +410,7 @@ func runQuery(
 	queryTelemetryDurationQuantiles []float64,
 	queryTelemetrySamplesQuantiles []int64,
 	queryTelemetrySeriesQuantiles []int64,
-	defaultEngine apiv1.PromqlEngineType,
+	defaultEngine string,
 	storeRateLimits store.SeriesSelectLimits,
 	queryMode queryMode,
 ) error {
@@ -713,7 +714,7 @@ func runQuery(
 			logger,
 			endpoints.GetEndpointStatus,
 			*engineFactory,
-			defaultEngine,
+			apiv1.PromqlEngineType(defaultEngine),
 			lookbackDeltaCreator,
 			queryableCreator,
 			// NOTE: Will share the same replica label as the query for now.
@@ -798,7 +799,8 @@ func runQuery(
 			info.WithQueryAPIInfoFunc(),
 		)
 
-		grpcAPI := apiv1.NewGRPCAPI(time.Now, queryReplicaLabels, queryableCreator, *engineFactory, defaultEngine, lookbackDeltaCreator, instantDefaultMaxSourceResolution)
+		defaultEngineType := querypb.EngineType(querypb.EngineType_value[defaultEngine])
+		grpcAPI := apiv1.NewGRPCAPI(time.Now, queryReplicaLabels, queryableCreator, *engineFactory, defaultEngineType, lookbackDeltaCreator, instantDefaultMaxSourceResolution)
 		storeServer := store.NewLimitedStoreServer(store.NewInstrumentedStoreServer(reg, proxy), reg, storeRateLimits)
 		s := grpcserver.New(logger, reg, tracer, grpcLogOpts, tagOpts, comp, grpcProbe,
 			grpcserver.WithServer(apiv1.RegisterQueryServer(grpcAPI)),

pkg/api/query/grpc.go

@@ -24,7 +24,7 @@ type GRPCAPI struct {
 	replicaLabels               []string
 	queryableCreate             query.QueryableCreator
 	engineFactory               QueryEngineFactory
-	defaultEngine               PromqlEngineType
+	defaultEngine               querypb.EngineType
 	lookbackDeltaCreate         func(int64) time.Duration
 	defaultMaxResolutionSeconds time.Duration
 }
@@ -34,7 +34,7 @@ func NewGRPCAPI(
 	replicaLabels []string,
 	creator query.QueryableCreator,
 	engineFactory QueryEngineFactory,
-	defaultEngine PromqlEngineType,
+	defaultEngine querypb.EngineType,
 	lookbackDeltaCreate func(int64) time.Duration,
 	defaultMaxResolutionSeconds time.Duration,
 ) *GRPCAPI {
@@ -104,15 +104,15 @@ func (g *GRPCAPI) Query(request *querypb.QueryRequest, server querypb.Query_Quer
 	)
 
 	var engine v1.QueryEngine
-	engineParam := PromqlEngineType(request.Engine)
-	if engineParam == "" {
+	engineParam := request.Engine
+	if engineParam == querypb.EngineType_default {
 		engineParam = g.defaultEngine
 	}
 
 	switch engineParam {
-	case PromqlEnginePrometheus:
+	case querypb.EngineType_prometheus:
 		engine = g.engineFactory.GetPrometheusEngine()
-	case PromqlEngineThanos:
+	case querypb.EngineType_thanos:
 		engine = g.engineFactory.GetThanosEngine()
 	default:
 		return status.Error(codes.InvalidArgument, "invalid engine parameter")
@@ -206,15 +206,15 @@ func (g *GRPCAPI) QueryRange(request *querypb.QueryRangeRequest, srv querypb.Que
 	interval := time.Duration(request.IntervalSeconds) * time.Second
 
 	var engine v1.QueryEngine
-	engineParam := PromqlEngineType(request.Engine)
-	if engineParam == "" {
+	engineParam := request.Engine
+	if engineParam == querypb.EngineType_default {
 		engineParam = g.defaultEngine
 	}
 
 	switch engineParam {
-	case PromqlEnginePrometheus:
+	case querypb.EngineType_prometheus:
 		engine = g.engineFactory.GetPrometheusEngine()
-	case PromqlEngineThanos:
+	case querypb.EngineType_thanos:
 		engine = g.engineFactory.GetThanosEngine()
 	default:
 		return status.Error(codes.InvalidArgument, "invalid engine parameter")

pkg/api/query/grpc_test.go

@@ -50,7 +50,7 @@ func TestGRPCQueryAPIErrorHandling(t *testing.T) {
 		engineFactory := QueryEngineFactory{
 			prometheusEngine: test.engine,
 		}
-		api := NewGRPCAPI(time.Now, nil, queryableCreator, engineFactory, PromqlEnginePrometheus, lookbackDeltaFunc, 0)
+		api := NewGRPCAPI(time.Now, nil, queryableCreator, engineFactory, querypb.EngineType_prometheus, lookbackDeltaFunc, 0)
 		t.Run("range_query", func(t *testing.T) {
 			rangeRequest := &querypb.QueryRangeRequest{
 				Query:            "metric",