CloudWatch: Datasource improvements (#20268)

* CloudWatch: Datasource improvements

* Add statistic as template variale

* Add wildcard to list of values

* Template variable intercept dimension key

* Return row specific errors when transformation error occured

* Add meta feedback

* Make it possible to retrieve values without known metrics

* Add curated dashboard for EC2

* Fix broken tests

* Use correct dashboard name

* Display alert in case multi template var is being used for some certain props in the cloudwatch query

* Minor fixes after feedback

* Update dashboard json

* Update snapshot test

* Make sure region default is intercepted in cloudwatch link

* Update dashboards

* Include ec2 dashboard in ds

* Do not include ec2 dashboard in beta1

* Display actual region

pkg/tsdb/cloudwatch/get_metric_data_executor.go

@@ -0,0 +1,34 @@
+package cloudwatch
+
+import (
+	"context"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/cloudwatch"
+	"github.com/grafana/grafana/pkg/infra/metrics"
+)
+
+func (e *CloudWatchExecutor) executeRequest(ctx context.Context, client cloudWatchClient, metricDataInput *cloudwatch.GetMetricDataInput) ([]*cloudwatch.GetMetricDataOutput, error) {
+	mdo := make([]*cloudwatch.GetMetricDataOutput, 0)
+
+	nextToken := ""
+	for {
+		if nextToken != "" {
+			metricDataInput.NextToken = aws.String(nextToken)
+		}
+		resp, err := client.GetMetricDataWithContext(ctx, metricDataInput)
+		if err != nil {
+			return mdo, err
+		}
+
+		mdo = append(mdo, resp)
+		metrics.MAwsCloudWatchGetMetricData.Add(float64(len(metricDataInput.MetricDataQueries)))
+
+		if resp.NextToken == nil || *resp.NextToken == "" {
+			break
+		}
+		nextToken = *resp.NextToken
+	}
+
+	return mdo, nil
+}