Do not store EvaluationString in Evaluation. (#44606)

* do not store evaluation string in Evaluation.
* reduce number of buckets to store for a single state

pkg/services/ngalert/api/api_prometheus.go

@@ -9,9 +9,9 @@ import (
 	"strings"
 	"time"
 
-	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	apiv1 "github.com/prometheus/client_golang/api/prometheus/v1"
 
+	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	ngmodels "github.com/grafana/grafana/pkg/services/ngalert/models"
 	"github.com/grafana/grafana/pkg/services/ngalert/store"
 
@@ -40,8 +40,8 @@ func (srv PrometheusSrv) RouteGetAlertStatuses(c *models.ReqContext) response.Re
 	for _, alertState := range srv.manager.GetAll(c.OrgId) {
 		startsAt := alertState.StartsAt
 		valString := ""
-		if len(alertState.Results) > 0 && alertState.State == eval.Alerting {
-			valString = alertState.Results[0].EvaluationString
+		if alertState.State == eval.Alerting {
+			valString = alertState.LastEvaluationString
 		}
 		alertResponse.Data.Alerts = append(alertResponse.Data.Alerts, &apimodels.Alert{
 			Labels:      map[string]string(alertState.Labels),
@@ -173,8 +173,8 @@ func (srv PrometheusSrv) RouteGetRuleStatuses(c *models.ReqContext) response.Res
 		for _, alertState := range srv.manager.GetStatesForRuleUID(c.OrgId, rule.UID) {
 			activeAt := alertState.StartsAt
 			valString := ""
-			if len(alertState.Results) > 0 && alertState.State == eval.Alerting {
-				valString = alertState.Results[0].EvaluationString
+			if alertState.State == eval.Alerting {
+				valString = alertState.LastEvaluationString
 			}
 			alert := &apimodels.Alert{
 				Labels:      map[string]string(alertState.Labels),

pkg/services/ngalert/schedule/compat.go

@@ -35,8 +35,8 @@ func stateToPostableAlert(alertState *state.State, appURL *url.URL) *models.Post
 	nL := alertState.Labels.Copy()
 	nA := data.Labels(alertState.Annotations).Copy()
 
-	if len(alertState.Results) > 0 {
-		nA["__value_string__"] = alertState.Results[0].EvaluationString
+	if alertState.LastEvaluationString != "" {
+		nA["__value_string__"] = alertState.LastEvaluationString
 	}
 
 	var urlStr string

pkg/services/ngalert/schedule/compat_test.go

@@ -100,11 +100,7 @@ func Test_stateToPostableAlert(t *testing.T) {
 					alertState := randomState(tc.state)
 					alertState.Annotations = randomMapOfStrings()
 					expectedValueString := util.GenerateShortUID()
-					alertState.Results = []state.Evaluation{
-						{
-							EvaluationString: expectedValueString,
-						},
-					}
+					alertState.LastEvaluationString = expectedValueString
 
 					result := stateToPostableAlert(alertState, appURL)
 

pkg/services/ngalert/state/manager.go

@@ -101,7 +101,7 @@ func (st *Manager) Warm() {
 				CacheId:              cacheId,
 				Labels:               lbs,
 				State:                translateInstanceState(entry.CurrentState),
-				Results:            []Evaluation{},
+				LastEvaluationString: "",
 				StartsAt:             entry.CurrentStateSince,
 				EndsAt:               entry.CurrentStateEnd,
 				LastEvaluationTime:   entry.LastEvalTime,
@@ -160,9 +160,9 @@ func (st *Manager) setNextState(ctx context.Context, alertRule *ngModels.AlertRu
 	currentState.Results = append(currentState.Results, Evaluation{
 		EvaluationTime:  result.EvaluatedAt,
 		EvaluationState: result.State,
-		EvaluationString: result.EvaluationString,
 		Values:          NewEvaluationValues(result.Values),
 	})
+	currentState.LastEvaluationString = result.EvaluationString
 	currentState.TrimResults(alertRule)
 	oldState := currentState.State
 

pkg/services/ngalert/state/manager_test.go

@@ -437,16 +437,6 @@ func TestProcessEvalResults(t *testing.T) {
 					},
 					State: eval.Pending,
 					Results: []state.Evaluation{
-						{
-							EvaluationTime:  evaluationTime.Add(10 * time.Second),
-							EvaluationState: eval.Alerting,
-							Values:          make(map[string]*float64),
-						},
-						{
-							EvaluationTime:  evaluationTime.Add(20 * time.Second),
-							EvaluationState: eval.NoData,
-							Values:          make(map[string]*float64),
-						},
 						{
 							EvaluationTime:  evaluationTime.Add(30 * time.Second),
 							EvaluationState: eval.Alerting,
@@ -528,16 +518,6 @@ func TestProcessEvalResults(t *testing.T) {
 					},
 					State: eval.NoData,
 					Results: []state.Evaluation{
-						{
-							EvaluationTime:  evaluationTime,
-							EvaluationState: eval.Alerting,
-							Values:          make(map[string]*float64),
-						},
-						{
-							EvaluationTime:  evaluationTime.Add(10 * time.Second),
-							EvaluationState: eval.Alerting,
-							Values:          make(map[string]*float64),
-						},
 						{
 							EvaluationTime:  evaluationTime.Add(20 * time.Second),
 							EvaluationState: eval.Alerting,
@@ -1336,11 +1316,6 @@ func TestProcessEvalResults(t *testing.T) {
 					},
 					State: eval.Alerting,
 					Results: []state.Evaluation{
-						{
-							EvaluationTime:  evaluationTime,
-							EvaluationState: eval.Normal,
-							Values:          make(map[string]*float64),
-						},
 						{
 							EvaluationTime:  evaluationTime.Add(30 * time.Second),
 							EvaluationState: eval.Alerting,
@@ -1428,11 +1403,6 @@ func TestProcessEvalResults(t *testing.T) {
 					},
 					State: eval.NoData,
 					Results: []state.Evaluation{
-						{
-							EvaluationTime:  evaluationTime,
-							EvaluationState: eval.Normal,
-							Values:          make(map[string]*float64),
-						},
 						{
 							EvaluationTime:  evaluationTime.Add(30 * time.Second),
 							EvaluationState: eval.Alerting,

pkg/services/ngalert/state/state.go

@@ -18,6 +18,7 @@ type State struct {
 	State                eval.State
 	Resolved             bool
 	Results              []Evaluation
+	LastEvaluationString string
 	StartsAt             time.Time
 	EndsAt               time.Time
 	LastEvaluationTime   time.Time
@@ -31,7 +32,6 @@ type State struct {
 type Evaluation struct {
 	EvaluationTime  time.Time
 	EvaluationState eval.State
-	EvaluationString string
 	// Values contains the RefID and value of reduce and math expressions.
 	// It does not contain values for classic conditions as the values
 	// in classic conditions do not have a RefID.
@@ -152,7 +152,7 @@ func (a *State) Equals(b *State) bool {
 }
 
 func (a *State) TrimResults(alertRule *ngModels.AlertRule) {
-	numBuckets := 2 * (int64(alertRule.For.Seconds()) / alertRule.IntervalSeconds)
+	numBuckets := int64(alertRule.For.Seconds()) / alertRule.IntervalSeconds
 	if numBuckets == 0 {
 		numBuckets = 10 // keep at least 10 evaluations in the event For is set to 0
 	}