Query Service: Combine SSE handling in single tenant and multi tenant paths (#108041)

* parse via sse

I need to figure out how to handle the pipeline.execute with our own
client. I think this is important for MT reasons, just like using our
own cache (via legacy) is important.

parsing is done though!

* WIP nonsense

* horrible code but i think it works

* Add support for sql expressions config settings

* Cleanup:
- remove spew from nodes.go
- uncomment out plugin context and use in single tenant flow
- make code more readable and add comments

* Cleanup:
- create separate file for mt ds client builder
- ensure error handling is the same for both expressions and regular queries
- other cleanup

* not working but good thoughts

* WIP, vector not working for non sse

* super hacky but i think vectors work now

* delete delete delete

* Comments for future ref

* break out query handling and start test

* add prom debugger

* clean up: remove comments and commented out bits

* fix query_test

* add prom debugger

* create table-driven tests with testsdata files

* Fix test

* Add test

* go mod??

* idk

* Remove comment

* go enterprise issue maybe

* Fix codeowners

* Delete

* Remove test data

* Clean up

* logger

* Remove go changes hopefully

* idk go man

* sad

* idk i ran go mod tidy and this is what it wants

* Fix readme, with much help from adam

* some linting and testing errors

* lint

* fix lint

* fix lint register.go

* another lint

* address lint in test

* fix dead code and linters for query_test

* Go mod?

* Struggling with go mod

* Fix test

* Fix another test

* Revert headers change

* Its difficult to test this in OSS as it depends on functionality defined in enterprise, let's bring these tests back in some form in enterprise

* Fix codeowners

---------

Co-authored-by: Adam Simpson <adam@adamsimpson.net>

pkg/expr/nodes.go

@@ -213,7 +213,7 @@ func (dn *DSNode) NeedsVars() []string {
 	return []string{}
 }
 
-func (s *Service) buildDSNode(dp *simple.DirectedGraph, rn *rawNode, req *Request) (*DSNode, error) {
+func (s *Service) buildDSNode(_ *simple.DirectedGraph, rn *rawNode, req *Request) (*DSNode, error) {
 	if rn.TimeRange == nil {
 		return nil, fmt.Errorf("time range must be specified for refID %s", rn.RefID)
 	}
@@ -361,17 +361,12 @@ func (dn *DSNode) Execute(ctx context.Context, now time.Time, _ mathexp.Vars, s
 	ctx, span := s.tracer.Start(ctx, "SSE.ExecuteDatasourceQuery")
 	defer span.End()
 
-	pCtx, err := s.pCtxProvider.GetWithDataSource(ctx, dn.datasource.Type, dn.request.User, dn.datasource)
-	if err != nil {
-		return mathexp.Results{}, err
-	}
 	span.SetAttributes(
 		attribute.String("datasource.type", dn.datasource.Type),
 		attribute.String("datasource.uid", dn.datasource.UID),
 	)
 
 	req := &backend.QueryDataRequest{
-		PluginContext: pCtx,
 		Queries: []backend.DataQuery{
 			{
 				RefID:         dn.refID,
@@ -399,9 +394,38 @@ func (dn *DSNode) Execute(ctx context.Context, now time.Time, _ mathexp.Vars, s
 		s.metrics.DSRequests.WithLabelValues(respStatus, fmt.Sprintf("%t", useDataplane), dn.datasource.Type).Inc()
 	}()
 
-	resp, err := s.dataService.QueryData(ctx, req)
-	if err != nil {
-		return mathexp.Results{}, MakeQueryError(dn.refID, dn.datasource.UID, err)
+	var resp *backend.QueryDataResponse
+	mtDSClient, ok := s.mtDatasourceClientBuilder.BuildClient(dn.datasource.Type, dn.datasource.UID)
+	if !ok { // use single tenant client
+		pCtx, err := s.pCtxProvider.GetWithDataSource(ctx, dn.datasource.Type, dn.request.User, dn.datasource)
+		if err != nil {
+			return mathexp.Results{}, err
+		}
+		req.PluginContext = pCtx
+		resp, err = s.dataService.QueryData(ctx, req)
+		if err != nil {
+			return mathexp.Results{}, MakeQueryError(dn.refID, dn.datasource.UID, err)
+		}
+	} else {
+		// transform request from backend.QueryDataRequest to k8s request
+		k8sReq := &data.QueryDataRequest{}
+		for _, q := range req.Queries {
+			var dataQuery data.DataQuery
+			err := json.Unmarshal(q.JSON, &dataQuery)
+			if err != nil {
+				return mathexp.Results{}, MakeQueryError(dn.refID, dn.datasource.UID, err)
+			}
+
+			k8sReq.Queries = append(k8sReq.Queries, dataQuery)
+		}
+		var err error
+		// make the query with a mt client
+		resp, err = mtDSClient.QueryData(ctx, *k8sReq)
+
+		// handle error
+		if err != nil {
+			return mathexp.Results{}, MakeQueryError(dn.refID, dn.datasource.UID, err)
+		}
 	}
 
 	dataFrames, err := getResponseFrame(logger, resp, dn.refID)