diff --git a/pkg/expr/graph.go b/pkg/expr/graph.go
index 260af692e92..6f02526d104 100644
--- a/pkg/expr/graph.go
+++ b/pkg/expr/graph.go
@@ -157,7 +157,7 @@ func (s *Service) buildGraph(req *Request) (*simple.DirectedGraph, error) {
 		case dsName == DatasourceName || dsUID == DatasourceUID:
 			node, err = buildCMDNode(dp, rn)
 		default: // If it's not an expression query, it's a data source query.
-			node, err = s.buildDSNode(dp, rn, req.OrgId)
+			node, err = s.buildDSNode(dp, rn, req)
 		}
 		if err != nil {
 			return nil, err
diff --git a/pkg/expr/nodes.go b/pkg/expr/nodes.go
index 616015aace3..f88d054e0a9 100644
--- a/pkg/expr/nodes.go
+++ b/pkg/expr/nodes.go
@@ -142,6 +142,7 @@ type DSNode struct {
 	timeRange  TimeRange
 	intervalMS int64
 	maxDP      int64
+	request    Request
 }
 
 // NodeType returns the data pipeline node type.
@@ -149,7 +150,7 @@ func (dn *DSNode) NodeType() NodeType {
 	return TypeDatasourceNode
 }
 
-func (s *Service) buildDSNode(dp *simple.DirectedGraph, rn *rawNode, orgID int64) (*DSNode, error) {
+func (s *Service) buildDSNode(dp *simple.DirectedGraph, rn *rawNode, req *Request) (*DSNode, error) {
 	encodedQuery, err := json.Marshal(rn.Query)
 	if err != nil {
 		return nil, err
@@ -160,12 +161,13 @@ func (s *Service) buildDSNode(dp *simple.DirectedGraph, rn *rawNode, orgID int64
 			id:    dp.NewNode().ID(),
 			refID: rn.RefID,
 		},
-		orgID:      orgID,
+		orgID:      req.OrgId,
 		query:      json.RawMessage(encodedQuery),
 		queryType:  rn.QueryType,
 		intervalMS: defaultIntervalMS,
 		maxDP:      defaultMaxDP,
 		timeRange:  rn.TimeRange,
+		request:    *req,
 	}
 
 	rawDsID, ok := rn.Query["datasourceId"]
@@ -231,6 +233,7 @@ func (dn *DSNode) Execute(ctx context.Context, vars mathexp.Vars, s *Service) (m
 	resp, err := s.queryData(ctx, &backend.QueryDataRequest{
 		PluginContext: pc,
 		Queries:       q,
+		Headers:       dn.request.Headers,
 	})
 
 	if err != nil {
diff --git a/pkg/expr/transform.go b/pkg/expr/transform.go
index c5d31560862..11416b7e4ac 100644
--- a/pkg/expr/transform.go
+++ b/pkg/expr/transform.go
@@ -206,6 +206,7 @@ func (s *Service) queryData(ctx context.Context, req *backend.QueryDataRequest)
 	tQ := plugins.DataQuery{
 		TimeRange: &timeRange,
 		Queries:   queries,
+		Headers:   req.Headers,
 	}
 
 	// Execute the converted queries
diff --git a/pkg/services/ngalert/eval/eval.go b/pkg/services/ngalert/eval/eval.go
index 475cd442153..c7fd9cf2373 100644
--- a/pkg/services/ngalert/eval/eval.go
+++ b/pkg/services/ngalert/eval/eval.go
@@ -117,6 +117,10 @@ type AlertExecCtx struct {
 func GetExprRequest(ctx AlertExecCtx, data []models.AlertQuery, now time.Time) (*expr.Request, error) {
 	req := &expr.Request{
 		OrgId: ctx.OrgID,
+		Headers: map[string]string{
+			// Some data sources check this in query method as sometimes alerting needs special considerations.
+			"FromAlert": "true",
+		},
 	}
 
 	for i := range data {
diff --git a/pkg/tsdb/cloudwatch/annotation_query.go b/pkg/tsdb/cloudwatch/annotation_query.go
index 1a427afaaeb..81dd9ccb72e 100644
--- a/pkg/tsdb/cloudwatch/annotation_query.go
+++ b/pkg/tsdb/cloudwatch/annotation_query.go
@@ -21,10 +21,7 @@ func (e *cloudWatchExecutor) executeAnnotationQuery(ctx context.Context, model *
 	namespace := model.Get("namespace").MustString("")
 	metricName := model.Get("metricName").MustString("")
 	dimensions := model.Get("dimensions").MustMap()
-	statistics, err := parseStatistics(model)
-	if err != nil {
-		return nil, err
-	}
+	statistics := parseStatistics(model)
 	period := int64(model.Get("period").MustInt(0))
 	if period == 0 && !usePrefixMatch {
 		period = 300
diff --git a/pkg/tsdb/cloudwatch/request_parser.go b/pkg/tsdb/cloudwatch/request_parser.go
index 8a9f10a368e..d27410b653c 100644
--- a/pkg/tsdb/cloudwatch/request_parser.go
+++ b/pkg/tsdb/cloudwatch/request_parser.go
@@ -2,6 +2,7 @@ package cloudwatch
 
 import (
 	"errors"
+	"fmt"
 	"math"
 	"regexp"
 	"sort"
@@ -52,20 +53,17 @@ func parseRequestQuery(model *simplejson.Json, refId string, startTime time.Time
 	}
 	namespace, err := model.Get("namespace").String()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get namespace: %v", err)
 	}
 	metricName, err := model.Get("metricName").String()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to get metricName: %v", err)
 	}
 	dimensions, err := parseDimensions(model)
 	if err != nil {
-		return nil, err
-	}
-	statistics, err := parseStatistics(model)
-	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to parse dimensions: %v", err)
 	}
+	statistics := parseStatistics(model)
 
 	p := model.Get("period").MustString("")
 	var period int
@@ -84,12 +82,12 @@ func parseRequestQuery(model *simplejson.Json, refId string, startTime time.Time
 		if reNumber.Match([]byte(p)) {
 			period, err = strconv.Atoi(p)
 			if err != nil {
-				return nil, err
+				return nil, fmt.Errorf("failed to parse period as integer: %v", err)
 			}
 		} else {
 			d, err := time.ParseDuration(p)
 			if err != nil {
-				return nil, err
+				return nil, fmt.Errorf("failed to parse period as duration: %v", err)
 			}
 			period = int(d.Seconds())
 		}
@@ -125,13 +123,13 @@ func parseRequestQuery(model *simplejson.Json, refId string, startTime time.Time
 	}, nil
 }
 
-func parseStatistics(model *simplejson.Json) ([]string, error) {
+func parseStatistics(model *simplejson.Json) []string {
 	var statistics []string
 	for _, s := range model.Get("statistics").MustArray() {
 		statistics = append(statistics, s.(string))
 	}
 
-	return statistics, nil
+	return statistics
 }
 
 func parseDimensions(model *simplejson.Json) (map[string][]string, error) {
@@ -145,7 +143,7 @@ func parseDimensions(model *simplejson.Json) (map[string][]string, error) {
 				parsedDimensions[k] = append(parsedDimensions[k], value.(string))
 			}
 		} else {
-			return nil, errors.New("failed to parse dimensions")
+			return nil, errors.New("unknown type as dimension value")
 		}
 	}