grafana/pkg/registry/apis/query/query.go

package query

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/grafana/grafana-plugin-sdk-go/backend"
	"github.com/grafana/grafana-plugin-sdk-go/experimental/apis/data/v0alpha1"
	"go.opentelemetry.io/otel/attribute"
	"golang.org/x/sync/errgroup"

	query "github.com/grafana/grafana/pkg/apis/query/v0alpha1"
	"github.com/grafana/grafana/pkg/expr/mathexp"
	"github.com/grafana/grafana/pkg/infra/log"
	"github.com/grafana/grafana/pkg/services/datasources"
	"github.com/grafana/grafana/pkg/util/errutil"
	"github.com/grafana/grafana/pkg/util/errutil/errhttp"
	"github.com/grafana/grafana/pkg/web"
)

// The query method (not really a create)
func (b *QueryAPIBuilder) doQuery(w http.ResponseWriter, r *http.Request) {
	ctx, span := b.tracer.Start(r.Context(), "QueryService.Query")
	defer span.End()

	raw := &query.QueryDataRequest{}
	err := web.Bind(r, raw)
	if err != nil {
		errhttp.Write(ctx, errutil.BadRequest(
			"query.bind",
			errutil.WithPublicMessage("Error reading query")).
			Errorf("error reading: %w", err), w)
		return
	}

	// Parses the request and splits it into multiple sub queries (if necessary)
	req, err := b.parser.parseRequest(ctx, raw)
	if err != nil {
		if errors.Is(err, datasources.ErrDataSourceNotFound) {
			errhttp.Write(ctx, errutil.BadRequest(
				"query.datasource.notfound",
				errutil.WithPublicMessage(err.Error())), w)
			return
		}
		errhttp.Write(ctx, err, w)
		return
	}

	// Actually run the query
	rsp, err := b.execute(ctx, req)
	if err != nil {
		errhttp.Write(ctx, errutil.Internal(
			"query.execution",
			errutil.WithPublicMessage("Error executing query")).
			Errorf("execution error: %w", err), w)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(query.GetResponseCode(rsp))
	_ = json.NewEncoder(w).Encode(rsp)
}

func (b *QueryAPIBuilder) execute(ctx context.Context, req parsedRequestInfo) (qdr *backend.QueryDataResponse, err error) {
	switch len(req.Requests) {
	case 0:
		break // nothing to do
	case 1:
		qdr, err = b.handleQuerySingleDatasource(ctx, req.Requests[0])
	default:
		qdr, err = b.executeConcurrentQueries(ctx, req.Requests)
	}

	if len(req.Expressions) > 0 {
		qdr, err = b.handleExpressions(ctx, req, qdr)
	}

	// Remove hidden results
	for _, refId := range req.HideBeforeReturn {
		r, ok := qdr.Responses[refId]
		if ok && r.Error == nil {
			delete(qdr.Responses, refId)
		}
	}
	return
}

// Process a single request
// See: https://github.com/grafana/grafana/blob/v10.2.3/pkg/services/query/query.go#L242
func (b *QueryAPIBuilder) handleQuerySingleDatasource(ctx context.Context, req datasourceRequest) (*backend.QueryDataResponse, error) {
	ctx, span := b.tracer.Start(ctx, "Query.handleQuerySingleDatasource")
	defer span.End()
	span.SetAttributes(
		attribute.String("datasource.type", req.PluginId),
		attribute.String("datasource.uid", req.UID),
	)

	allHidden := true
	for idx := range req.Request.Queries {
		if !req.Request.Queries[idx].Hide {
			allHidden = false
			break
		}
	}
	if allHidden {
		return &backend.QueryDataResponse{}, nil
	}

	// Add user headers... here or in client.QueryData
	client, err := b.client.GetDataSourceClient(ctx, v0alpha1.DataSourceRef{
		Type: req.PluginId,
		UID:  req.UID,
	})
	if err != nil {
		return nil, err
	}

	code, rsp, err := client.QueryData(ctx, *req.Request)
	if err == nil && rsp != nil {
		for _, q := range req.Request.Queries {
			if q.ResultAssertions != nil {
				result, ok := rsp.Responses[q.RefID]
				if ok && result.Error == nil {
					err = q.ResultAssertions.Validate(result.Frames)
					if err != nil {
						result.Error = err
						result.ErrorSource = backend.ErrorSourceDownstream
						rsp.Responses[q.RefID] = result
					}
				}
			}
		}
	}

	// Create a response object with the error when missing (happens for client errors like 404)
	if rsp == nil && err != nil {
		rsp = &backend.QueryDataResponse{Responses: make(backend.Responses)}
		for _, q := range req.Request.Queries {
			rsp.Responses[q.RefID] = backend.DataResponse{
				Status: backend.Status(code),
				Error:  err,
			}
		}
	}
	return rsp, err
}

// buildErrorResponses applies the provided error to each query response in the list. These queries should all belong to the same datasource.
func buildErrorResponse(err error, req datasourceRequest) *backend.QueryDataResponse {
	rsp := backend.NewQueryDataResponse()
	for _, query := range req.Request.Queries {
		rsp.Responses[query.RefID] = backend.DataResponse{
			Error: err,
		}
	}
	return rsp
}

// executeConcurrentQueries executes queries to multiple datasources concurrently and returns the aggregate result.
func (b *QueryAPIBuilder) executeConcurrentQueries(ctx context.Context, requests []datasourceRequest) (*backend.QueryDataResponse, error) {
	ctx, span := b.tracer.Start(ctx, "Query.executeConcurrentQueries")
	defer span.End()

	g, ctx := errgroup.WithContext(ctx)
	g.SetLimit(b.concurrentQueryLimit) // prevent too many concurrent requests
	rchan := make(chan *backend.QueryDataResponse, len(requests))

	// Create panic recovery function for loop below
	recoveryFn := func(req datasourceRequest) {
		if r := recover(); r != nil {
			var err error
			b.log.Error("query datasource panic", "error", r, "stack", log.Stack(1))
			if theErr, ok := r.(error); ok {
				err = theErr
			} else if theErrString, ok := r.(string); ok {
				err = fmt.Errorf(theErrString)
			} else {
				err = fmt.Errorf("unexpected error - %s", b.userFacingDefaultError)
			}
			// Due to the panic, there is no valid response for any query for this datasource. Append an error for each one.
			rchan <- buildErrorResponse(err, req)
		}
	}

	// Query each datasource concurrently
	for idx := range requests {
		req := requests[idx]
		g.Go(func() error {
			defer recoveryFn(req)

			dqr, err := b.handleQuerySingleDatasource(ctx, req)
			if err == nil {
				rchan <- dqr
			} else {
				rchan <- buildErrorResponse(err, req)
			}
			return nil
		})
	}

	if err := g.Wait(); err != nil {
		return nil, err
	}
	close(rchan)

	// Merge the results from each response
	resp := backend.NewQueryDataResponse()
	for result := range rchan {
		for refId, dataResponse := range result.Responses {
			resp.Responses[refId] = dataResponse
		}
	}

	return resp, nil
}

// Unlike the implementation in expr/node.go, all datasource queries have been processed first
func (b *QueryAPIBuilder) handleExpressions(ctx context.Context, req parsedRequestInfo, data *backend.QueryDataResponse) (qdr *backend.QueryDataResponse, err error) {
	start := time.Now()
	ctx, span := b.tracer.Start(ctx, "SSE.handleExpressions")
	defer func() {
		var respStatus string
		switch {
		case err == nil:
			respStatus = "success"
		default:
			respStatus = "failure"
		}
		duration := float64(time.Since(start).Nanoseconds()) / float64(time.Millisecond)
		b.metrics.expressionsQuerySummary.WithLabelValues(respStatus).Observe(duration)

		span.End()
	}()

	qdr = data
	if qdr == nil {
		qdr = &backend.QueryDataResponse{}
	}
	if qdr.Responses == nil {
		qdr.Responses = make(backend.Responses) // avoid NPE for lookup
	}
	now := start // <<< this should come from the original query parser
	vars := make(mathexp.Vars)
	for _, expression := range req.Expressions {
		// Setup the variables
		for _, refId := range expression.Command.NeedsVars() {
			_, ok := vars[refId]
			if !ok {
				dr, ok := qdr.Responses[refId]
				if ok {
					allowLongFrames := false // TODO -- depends on input type and only if SQL?
					_, res, err := b.converter.Convert(ctx, req.RefIDTypes[refId], dr.Frames, allowLongFrames)
					if err != nil {
						res.Error = err
					}
					vars[refId] = res
				} else {
					// This should error in the parsing phase
					err := fmt.Errorf("missing variable %s for %s", refId, expression.RefID)
					qdr.Responses[refId] = backend.DataResponse{
						Error: err,
					}
					return qdr, err
				}
			}
		}

		refId := expression.RefID
		results, err := expression.Command.Execute(ctx, now, vars, b.tracer)
		if err != nil {
			results.Error = err
		}
		qdr.Responses[refId] = backend.DataResponse{
			Error:  results.Error,
			Frames: results.Values.AsDataFrames(refId),
		}
	}
	return qdr, nil
}