prom: add support for default step param (#9866)

Alerting for prometheus have been depending on the step parameter from each query.
In https://github.com/grafana/grafana/pull/9226 we changed the behavior for step in the
frontend which caused problems for alerting. This commit fixes that by introducing a default
min interval value so alerting always have something to depend on. 

closes #9777

pkg/tsdb/influxdb/model_parser.go

@@ -2,9 +2,11 @@ package influxdb
 
 import (
 	"strconv"
+	"time"
 
 	"github.com/grafana/grafana/pkg/components/simplejson"
 	"github.com/grafana/grafana/pkg/models"
+	"github.com/grafana/grafana/pkg/tsdb"
 )
 
 type InfluxdbQueryParser struct{}
@@ -37,13 +39,7 @@ func (qp *InfluxdbQueryParser) Parse(model *simplejson.Json, dsInfo *models.Data
 		return nil, err
 	}
 
-	interval := model.Get("interval").MustString("")
-	if interval == "" && dsInfo.JsonData != nil {
-		dsInterval := dsInfo.JsonData.Get("timeInterval").MustString("")
-		if dsInterval != "" {
-			interval = dsInterval
-		}
-	}
+	parsedInterval, err := tsdb.GetIntervalFrom(dsInfo, model, time.Millisecond*1)
 
 	return &Query{
 		Measurement:  measurement,
@@ -53,7 +49,7 @@ func (qp *InfluxdbQueryParser) Parse(model *simplejson.Json, dsInfo *models.Data
 		Tags:         tags,
 		Selects:      selects,
 		RawQuery:     rawQuery,
-		Interval:     interval,
+		Interval:     parsedInterval,
 		Alias:        alias,
 		UseRawQuery:  useRawQuery,
 	}, nil

pkg/tsdb/influxdb/model_parser_test.go

@@ -2,6 +2,7 @@ package influxdb
 
 import (
 	"testing"
+	"time"
 
 	"github.com/grafana/grafana/pkg/components/simplejson"
 	"github.com/grafana/grafana/pkg/models"
@@ -115,7 +116,7 @@ func TestInfluxdbQueryParser(t *testing.T) {
 			So(len(res.GroupBy), ShouldEqual, 3)
 			So(len(res.Selects), ShouldEqual, 3)
 			So(len(res.Tags), ShouldEqual, 2)
-			So(res.Interval, ShouldEqual, ">20s")
+			So(res.Interval, ShouldEqual, time.Second*20)
 			So(res.Alias, ShouldEqual, "serie alias")
 		})
 
@@ -174,7 +175,7 @@ func TestInfluxdbQueryParser(t *testing.T) {
 			So(len(res.GroupBy), ShouldEqual, 2)
 			So(len(res.Selects), ShouldEqual, 1)
 			So(len(res.Tags), ShouldEqual, 0)
-			So(res.Interval, ShouldEqual, ">10s")
+			So(res.Interval, ShouldEqual, time.Second*10)
 		})
 	})
 }

pkg/tsdb/influxdb/models.go

@@ -1,5 +1,7 @@
 package influxdb
 
+import "time"
+
 type Query struct {
 	Measurement  string
 	Policy       string
@@ -10,8 +12,7 @@ type Query struct {
 	RawQuery     string
 	UseRawQuery  bool
 	Alias        string
-
-	Interval string
+	Interval     time.Duration
 }
 
 type Tag struct {

pkg/tsdb/influxdb/query.go

@@ -29,10 +29,8 @@ func (query *Query) Build(queryContext *tsdb.TsdbQuery) (string, error) {
 		res += query.renderGroupBy(queryContext)
 	}
 
-	interval, err := getDefinedInterval(query, queryContext)
-	if err != nil {
-		return "", err
-	}
+	calculator := tsdb.NewIntervalCalculator(&tsdb.IntervalOptions{})
+	interval := calculator.Calculate(queryContext.TimeRange, query.Interval)
 
 	res = strings.Replace(res, "$timeFilter", query.renderTimeFilter(queryContext), -1)
 	res = strings.Replace(res, "$interval", interval.Text, -1)
@@ -41,29 +39,6 @@ func (query *Query) Build(queryContext *tsdb.TsdbQuery) (string, error) {
 	return res, nil
 }
 
-func getDefinedInterval(query *Query, queryContext *tsdb.TsdbQuery) (*tsdb.Interval, error) {
-	defaultInterval := tsdb.CalculateInterval(queryContext.TimeRange)
-
-	if query.Interval == "" {
-		return &defaultInterval, nil
-	}
-
-	setInterval := strings.Replace(strings.Replace(query.Interval, "<", "", 1), ">", "", 1)
-	parsedSetInterval, err := time.ParseDuration(setInterval)
-
-	if err != nil {
-		return nil, err
-	}
-
-	if strings.Contains(query.Interval, ">") {
-		if defaultInterval.Value > parsedSetInterval {
-			return &defaultInterval, nil
-		}
-	}
-
-	return &tsdb.Interval{Value: parsedSetInterval, Text: setInterval}, nil
-}
-
 func (query *Query) renderTags() []string {
 	var res []string
 	for i, tag := range query.Tags {

pkg/tsdb/influxdb/query_test.go

@@ -2,6 +2,7 @@ package influxdb
 
 import (
 	"testing"
+	"time"
 
 	"strings"
 
@@ -38,7 +39,7 @@ func TestInfluxdbQueryBuilder(t *testing.T) {
 				Measurement: "cpu",
 				Policy:      "policy",
 				GroupBy:     []*QueryPart{groupBy1, groupBy3},
-				Interval:    "10s",
+				Interval:    time.Second * 10,
 			}
 
 			rawQuery, err := query.Build(queryContext)
@@ -52,7 +53,7 @@ func TestInfluxdbQueryBuilder(t *testing.T) {
 				Measurement: "cpu",
 				GroupBy:     []*QueryPart{groupBy1, groupBy2, groupBy3},
 				Tags:        []*Tag{tag1, tag2},
-				Interval:    "5s",
+				Interval:    time.Second * 5,
 			}
 
 			rawQuery, err := query.Build(queryContext)
@@ -64,7 +65,7 @@ func TestInfluxdbQueryBuilder(t *testing.T) {
 			query := &Query{
 				Selects:     []*Select{{*qp1, *qp2, *mathPartDivideBy100}},
 				Measurement: "cpu",
-				Interval:    "5s",
+				Interval:    time.Second * 5,
 			}
 
 			rawQuery, err := query.Build(queryContext)
@@ -76,7 +77,7 @@ func TestInfluxdbQueryBuilder(t *testing.T) {
 			query := &Query{
 				Selects:     []*Select{{*qp1, *qp2, *mathPartDivideByIntervalMs}},
 				Measurement: "cpu",
-				Interval:    "5s",
+				Interval:    time.Second * 5,
 			}
 
 			rawQuery, err := query.Build(queryContext)
@@ -117,7 +118,7 @@ func TestInfluxdbQueryBuilder(t *testing.T) {
 				Measurement: "cpu",
 				Policy:      "policy",
 				GroupBy:     []*QueryPart{groupBy1, groupBy3},
-				Interval:    "10s",
+				Interval:    time.Second * 10,
 				RawQuery:    "Raw query",
 				UseRawQuery: true,
 			}