feat: add last option to alert condition match type (#5929)

frontend/public/locales/en-GB/alerts.json

@@ -53,6 +53,7 @@
 	"option_atleastonce": "at least once",
 	"option_onaverage": "on average",
 	"option_intotal": "in total",
+	"option_last": "last",
 	"option_above": "above",
 	"option_below": "below",
 	"option_equal": "is equal to",

frontend/public/locales/en-GB/rules.json

@@ -40,6 +40,7 @@
 	"option_atleastonce": "at least once",
 	"option_onaverage": "on average",
 	"option_intotal": "in total",
+	"option_last": "last",
 	"option_above": "above",
 	"option_below": "below",
 	"option_equal": "is equal to",

frontend/public/locales/en/alerts.json

@@ -53,6 +53,7 @@
 	"option_atleastonce": "at least once",
 	"option_onaverage": "on average",
 	"option_intotal": "in total",
+	"option_last": "last",
 	"option_above": "above",
 	"option_below": "below",
 	"option_equal": "is equal to",

frontend/public/locales/en/rules.json

@@ -40,6 +40,7 @@
 	"option_atleastonce": "at least once",
 	"option_onaverage": "on average",
 	"option_intotal": "in total",
+	"option_last": "last",
 	"option_above": "above",
 	"option_below": "below",
 	"option_equal": "is equal to",

frontend/src/container/FormAlertRules/RuleOptions.tsx

@@ -103,6 +103,7 @@ function RuleOptions({
 			<Select.Option value="2">{t('option_allthetimes')}</Select.Option>
 			<Select.Option value="3">{t('option_onaverage')}</Select.Option>
 			<Select.Option value="4">{t('option_intotal')}</Select.Option>
+			<Select.Option value="5">{t('option_last')}</Select.Option>
 		</InlineSelect>
 	);
 

pkg/query-service/rules/alerting.go

@@ -112,6 +112,7 @@ const (
 	AllTheTimes   MatchType = "2"
 	OnAverage     MatchType = "3"
 	InTotal       MatchType = "4"
+	Last          MatchType = "5"
 )
 
 type RuleCondition struct {

pkg/query-service/rules/base_rule.go

@@ -483,6 +483,27 @@ func (r *BaseRule) shouldAlert(series v3.Series) (Sample, bool) {
 				shouldAlert = true
 			}
 		}
+	case Last:
+		// If the last sample matches the condition, the rule is firing.
+		shouldAlert = false
+		alertSmpl = Sample{Point: Point{V: series.Points[len(series.Points)-1].Value}, Metric: lblsNormalized, MetricOrig: lbls}
+		if r.compareOp() == ValueIsAbove {
+			if series.Points[len(series.Points)-1].Value > r.targetVal() {
+				shouldAlert = true
+			}
+		} else if r.compareOp() == ValueIsBelow {
+			if series.Points[len(series.Points)-1].Value < r.targetVal() {
+				shouldAlert = true
+			}
+		} else if r.compareOp() == ValueIsEq {
+			if series.Points[len(series.Points)-1].Value == r.targetVal() {
+				shouldAlert = true
+			}
+		} else if r.compareOp() == ValueIsNotEq {
+			if series.Points[len(series.Points)-1].Value != r.targetVal() {
+				shouldAlert = true
+			}
+		}
 	}
 	return alertSmpl, shouldAlert
 }

pkg/query-service/rules/threshold_rule_test.go

@@ -677,6 +677,111 @@ func TestThresholdRuleShouldAlert(t *testing.T) {
 			matchType:   "4", // InTotal
 			target:      20.0,
 		},
+		// Test cases for Last
+		// greater than last
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert:         true,
+			compareOp:           "1", // Greater Than
+			matchType:           "5", // Last
+			target:              5.0,
+			expectedAlertSample: v3.Point{Value: 10.0},
+		},
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert: false,
+			compareOp:   "1", // Greater Than
+			matchType:   "5", // Last
+			target:      20.0,
+		},
+		// less than last
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert:         true,
+			compareOp:           "2", // Less Than
+			matchType:           "5", // Last
+			target:              15.0,
+			expectedAlertSample: v3.Point{Value: 10.0},
+		},
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert: false,
+			compareOp:   "2", // Less Than
+			matchType:   "5", // Last
+			target:      5.0,
+		},
+		// equals last
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert:         true,
+			compareOp:           "3", // Equals
+			matchType:           "5", // Last
+			target:              10.0,
+			expectedAlertSample: v3.Point{Value: 10.0},
+		},
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert: false,
+			compareOp:   "3", // Equals
+			matchType:   "5", // Last
+			target:      5.0,
+		},
+		// not equals last
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert:         true,
+			compareOp:           "4", // Not Equals
+			matchType:           "5", // Last
+			target:              5.0,
+			expectedAlertSample: v3.Point{Value: 10.0},
+		},
+		{
+			values: v3.Series{
+				Points: []v3.Point{
+					{Value: 10.0},
+					{Value: 10.0},
+				},
+			},
+			expectAlert: false,
+			compareOp:   "4", // Not Equals
+			matchType:   "5", // Last
+			target:      10.0,
+		},
 	}
 
 	fm := featureManager.StartManager()