Expressions: Add option to disable feature (#30541)

* Expressions: Add option to disable feature

* Apply suggestions from code review

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/services/ngalert/api.go

@@ -39,7 +39,8 @@ func (ng *AlertNG) conditionEvalEndpoint(c *models.ReqContext, dto evalAlertCond
 		return response.Error(400, "invalid condition", err)
 	}
 
-	evalResults, err := eval.ConditionEval(&dto.Condition, timeNow())
+	evaluator := eval.Evaluator{Cfg: ng.Cfg}
+	evalResults, err := evaluator.ConditionEval(&dto.Condition, timeNow())
 	if err != nil {
 		return response.Error(400, "Failed to evaluate conditions", err)
 	}
@@ -69,7 +70,8 @@ func (ng *AlertNG) alertDefinitionEvalEndpoint(c *models.ReqContext) response.Re
 		return response.Error(400, "invalid condition", err)
 	}
 
-	evalResults, err := eval.ConditionEval(condition, timeNow())
+	evaluator := eval.Evaluator{Cfg: ng.Cfg}
+	evalResults, err := evaluator.ConditionEval(condition, timeNow())
 	if err != nil {
 		return response.Error(400, "Failed to evaluate alert", err)
 	}

pkg/services/ngalert/eval/eval.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/grafana/grafana/pkg/setting"
+
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana/pkg/expr"
@@ -14,6 +16,10 @@ import (
 
 const alertingEvaluationTimeout = 30 * time.Second
 
+type Evaluator struct {
+	Cfg *setting.Cfg
+}
+
 // invalidEvalResultFormatError is an error for invalid format of the alert definition evaluation results.
 type invalidEvalResultFormatError struct {
 	refID  string
@@ -87,7 +93,8 @@ func (c Condition) IsValid() bool {
 
 // AlertExecCtx is the context provided for executing an alert condition.
 type AlertExecCtx struct {
-	OrgID int64
+	OrgID              int64
+	ExpressionsEnabled bool
 
 	Ctx context.Context
 }
@@ -133,7 +140,8 @@ func (c *Condition) execute(ctx AlertExecCtx, now time.Time) (*ExecutionResults,
 		})
 	}
 
-	pbRes, err := expr.TransformData(ctx.Ctx, queryDataReq)
+	exprService := expr.Service{Cfg: &setting.Cfg{ExpressionsEnabled: ctx.ExpressionsEnabled}}
+	pbRes, err := exprService.TransformData(ctx.Ctx, queryDataReq)
 	if err != nil {
 		return &result, err
 	}
@@ -210,11 +218,11 @@ func (evalResults Results) AsDataFrame() data.Frame {
 }
 
 // ConditionEval executes conditions and evaluates the result.
-func ConditionEval(condition *Condition, now time.Time) (Results, error) {
+func (e *Evaluator) ConditionEval(condition *Condition, now time.Time) (Results, error) {
 	alertCtx, cancelFn := context.WithTimeout(context.Background(), alertingEvaluationTimeout)
 	defer cancelFn()
 
-	alertExecCtx := AlertExecCtx{OrgID: condition.OrgID, Ctx: alertCtx}
+	alertExecCtx := AlertExecCtx{OrgID: condition.OrgID, Ctx: alertCtx, ExpressionsEnabled: e.Cfg.ExpressionsEnabled}
 
 	execResult, err := condition.execute(alertExecCtx, now)
 	if err != nil {

pkg/services/ngalert/ngalert.go

@@ -47,7 +47,13 @@ func (ng *AlertNG) Init() error {
 	ng.log = log.New("ngalert")
 
 	ng.registerAPIEndpoints()
-	ng.schedule = newScheduler(clock.New(), baseIntervalSeconds*time.Second, ng.log, nil)
+	schedCfg := schedulerCfg{
+		c:            clock.New(),
+		baseInterval: baseIntervalSeconds * time.Second,
+		logger:       ng.log,
+		evaluator:    eval.Evaluator{Cfg: ng.Cfg},
+	}
+	ng.schedule = newScheduler(schedCfg)
 	return nil
 }
 

pkg/services/ngalert/schedule.go

@@ -47,7 +47,7 @@ func (ng *AlertNG) definitionRoutine(grafanaCtx context.Context, key alertDefini
 					OrgID:                 alertDefinition.OrgID,
 					QueriesAndExpressions: alertDefinition.Data,
 				}
-				results, err := eval.ConditionEval(&condition, ctx.now)
+				results, err := ng.schedule.evaluator.ConditionEval(&condition, ctx.now)
 				end = timeNow()
 				if err != nil {
 					// consider saving alert instance on error
@@ -118,19 +118,30 @@ type schedule struct {
 	stopApplied func(alertDefinitionKey)
 
 	log log.Logger
+
+	evaluator eval.Evaluator
+}
+
+type schedulerCfg struct {
+	c            clock.Clock
+	baseInterval time.Duration
+	logger       log.Logger
+	evalApplied  func(alertDefinitionKey, time.Time)
+	evaluator    eval.Evaluator
 }
 
 // newScheduler returns a new schedule.
-func newScheduler(c clock.Clock, baseInterval time.Duration, logger log.Logger, evalApplied func(alertDefinitionKey, time.Time)) *schedule {
-	ticker := alerting.NewTicker(c.Now(), time.Second*0, c, int64(baseInterval.Seconds()))
+func newScheduler(cfg schedulerCfg) *schedule {
+	ticker := alerting.NewTicker(cfg.c.Now(), time.Second*0, cfg.c, int64(cfg.baseInterval.Seconds()))
 	sch := schedule{
 		registry:     alertDefinitionRegistry{alertDefinitionInfo: make(map[alertDefinitionKey]alertDefinitionInfo)},
 		maxAttempts:  maxAttempts,
-		clock:        c,
-		baseInterval: baseInterval,
-		log:          logger,
+		clock:        cfg.c,
+		baseInterval: cfg.baseInterval,
+		log:          cfg.logger,
 		heartbeat:    ticker,
-		evalApplied:  evalApplied,
+		evalApplied:  cfg.evalApplied,
+		evaluator:    cfg.evaluator,
 	}
 	return &sch
 }

pkg/services/ngalert/schedule_test.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/grafana/grafana/pkg/infra/log"
 	"github.com/grafana/grafana/pkg/registry"
+	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -26,7 +27,13 @@ func TestAlertingTicker(t *testing.T) {
 	t.Cleanup(registry.ClearOverrides)
 
 	mockedClock := clock.NewMock()
-	ng.schedule = newScheduler(mockedClock, time.Second, log.New("ngalert.schedule.test"), nil)
+	schefCfg := schedulerCfg{
+		c:            mockedClock,
+		baseInterval: time.Second,
+		logger:       log.New("ngalert.schedule.test"),
+		evaluator:    eval.Evaluator{Cfg: ng.Cfg},
+	}
+	ng.schedule = newScheduler(schefCfg)
 
 	alerts := make([]*AlertDefinition, 0)