alert rule have to be pending before alerting is for is specified

pkg/services/alerting/eval_context.go

@@ -126,7 +126,7 @@ func (c *EvalContext) GetNewState() m.AlertStateType {
 	}
 
 	since := time.Now().Sub(c.Rule.LastStateChange)
-	if since > c.Rule.For {
+	if c.PrevAlertState == m.AlertStatePending && since > c.Rule.For {
 		return m.AlertStateAlerting
 	}
 

pkg/services/alerting/eval_context_test.go

@@ -66,8 +66,8 @@ func TestGetStateFromEvalContext(t *testing.T) {
 			},
 		},
 		{
-			name:     "ok -> alerting. since its been firing for more than FOR",
-			expected: models.AlertStateAlerting,
+			name:     "ok -> pending. since it has to be pending longer than FOR and prev state is ok",
+			expected: models.AlertStatePending,
 			applyFn: func(ec *EvalContext) {
 				ec.PrevAlertState = models.AlertStateOK
 				ec.Firing = true
@@ -75,6 +75,16 @@ func TestGetStateFromEvalContext(t *testing.T) {
 				ec.Rule.For = time.Minute * 2
 			},
 		},
+		{
+			name:     "pending -> alerting. since its been firing for more than FOR and prev state is pending",
+			expected: models.AlertStateAlerting,
+			applyFn: func(ec *EvalContext) {
+				ec.PrevAlertState = models.AlertStatePending
+				ec.Firing = true
+				ec.Rule.LastStateChange = time.Now().Add(-(time.Hour * 5))
+				ec.Rule.For = time.Minute * 2
+			},
+		},
 		{
 			name:     "alerting -> alerting. should not update regardless of FOR",
 			expected: models.AlertStateAlerting,