Query Frontend For Logical Query Plan Support

docs/configuration/config-file-reference.md

@@ -4451,6 +4451,11 @@ grpc_client_config:
 # URL of downstream Prometheus.
 # CLI flag: -frontend.downstream-url
 [downstream_url: <string> | default = ""]
+
+# Experimental: Enables distributed execution of queries by passing logical
+# query plan fragments to downstream components.
+# CLI flag: -frontend.distributed_exec_enabled
+[distributed_exec_enabled: <boolean> | default = false]
 ```
 
 ### `query_range_config`

pkg/cortex/modules.go

@@ -533,12 +533,13 @@ func (t *Cortex) initQueryFrontendTripperware() (serv services.Service, err erro
 		prometheusCodec,
 		shardedPrometheusCodec,
 		t.Cfg.Querier.LookbackDelta,
+		t.Cfg.Frontend.DistributedExecEnabled,
 	)
 	if err != nil {
 		return nil, err
 	}
 
-	instantQueryMiddlewares, err := instantquery.Middlewares(util_log.Logger, t.Overrides, instantQueryCodec, queryAnalyzer, t.Cfg.Querier.LookbackDelta)
+	instantQueryMiddlewares, err := instantquery.Middlewares(util_log.Logger, t.Overrides, instantQueryCodec, queryAnalyzer, t.Cfg.Querier.LookbackDelta, t.Cfg.Frontend.DistributedExecEnabled)
 	if err != nil {
 		return nil, err
 	}

pkg/frontend/config.go

@@ -20,7 +20,8 @@ type CombinedFrontendConfig struct {
 	FrontendV1 v1.Config               `yaml:",inline"`
 	FrontendV2 v2.Config               `yaml:",inline"`
 
-	DownstreamURL string `yaml:"downstream_url"`
+	DownstreamURL          string `yaml:"downstream_url"`
+	DistributedExecEnabled bool   `yaml:"distributed_exec_enabled"`
 }
 
 func (cfg *CombinedFrontendConfig) RegisterFlags(f *flag.FlagSet) {
@@ -29,6 +30,7 @@ func (cfg *CombinedFrontendConfig) RegisterFlags(f *flag.FlagSet) {
 	cfg.FrontendV2.RegisterFlags(f)
 
 	f.StringVar(&cfg.DownstreamURL, "frontend.downstream-url", "", "URL of downstream Prometheus.")
+	f.BoolVar(&cfg.DistributedExecEnabled, "frontend.distributed_exec_enabled", false, "Experimental: Enables distributed execution of queries by passing logical query plan fragments to downstream components.")
 }
 
 // InitFrontend initializes frontend (either V1 -- without scheduler, or V2 -- with scheduler) or no frontend at

pkg/querier/tripperware/instantquery/instant_query.go

@@ -23,6 +23,8 @@ import (
 	"github.com/cortexproject/cortex/pkg/util"
 	"github.com/cortexproject/cortex/pkg/util/limiter"
 	"github.com/cortexproject/cortex/pkg/util/spanlogger"
+
+	"github.com/thanos-io/promql-engine/logicalplan"
 )
 
 var (
@@ -141,6 +143,19 @@ func (c instantQueryCodec) DecodeResponse(ctx context.Context, r *http.Response,
 	return &resp, nil
 }
 
+func (c instantQueryCodec) getSerializedBody(promReq *tripperware.PrometheusRequest) ([]byte, error) {
+	var byteLP []byte
+	var err error
+
+	if promReq.LogicalPlan != nil {
+		byteLP, err = logicalplan.Marshal(promReq.LogicalPlan.Root())
+		if err != nil {
+			return nil, err
+		}
+	}
+	return byteLP, nil
+}
+
 func (c instantQueryCodec) EncodeRequest(ctx context.Context, r tripperware.Request) (*http.Request, error) {
 	promReq, ok := r.(*tripperware.PrometheusRequest)
 	if !ok {
@@ -168,17 +183,24 @@ func (c instantQueryCodec) EncodeRequest(ctx context.Context, r tripperware.Requ
 		}
 	}
 
+	h.Add("Content-Type", "application/json")
+
 	isSourceRuler := strings.Contains(h.Get("User-Agent"), tripperware.RulerUserAgent)
 	if !isSourceRuler {
 		// When the source is the Ruler, skip set header
 		tripperware.SetRequestHeaders(h, c.defaultCodecType, c.compression)
 	}
 
+	byteBody, err := c.getSerializedBody(promReq)
+	if err != nil {
+		return nil, err
+	}
+
 	req := &http.Request{
-		Method:     "GET",
+		Method:     "POST",
 		RequestURI: u.String(), // This is what the httpgrpc code looks at.
 		URL:        u,
-		Body:       http.NoBody,
+		Body:       io.NopCloser(bytes.NewReader(byteBody)),
 		Header:     h,
 	}
 

pkg/querier/tripperware/instantquery/instant_query_middlewares.go

@@ -15,10 +15,17 @@ func Middlewares(
 	merger tripperware.Merger,
 	queryAnalyzer querysharding.Analyzer,
 	lookbackDelta time.Duration,
+	distributedExecEnabled bool,
 ) ([]tripperware.Middleware, error) {
 	m := []tripperware.Middleware{
 		NewLimitsMiddleware(limits, lookbackDelta),
 		tripperware.ShardByMiddleware(log, limits, merger, queryAnalyzer),
 	}
+
+	if distributedExecEnabled {
+		m = append(m,
+			tripperware.LogicalPlanGenMiddleware())
+	}
+
 	return m, nil
 }