Improve comments related to Health events and scheduled changes

Author: AustinSiu

pkg/monitor/sqsevent/scheduled-change-event.go

@@ -67,7 +67,6 @@ type ScheduledChangeEventDetail struct {
 	AffectedEntities  []AffectedEntity `json:"affectedEntities"`
 }
 
-// func (m SQSMonitor) scheduledEventToInterruptionEvents(event EventBridgeEvent, message *sqs.Message) ([]InterruptionEventWrapper, error) {
 func (m SQSMonitor) scheduledEventToInterruptionEvents(event *EventBridgeEvent, message *sqs.Message) []InterruptionEventWrapper {
 	scheduledChangeEventDetail := &ScheduledChangeEventDetail{}
 	interruptionEventWrappers := []InterruptionEventWrapper{}
@@ -93,11 +92,13 @@ func (m SQSMonitor) scheduledEventToInterruptionEvents(event *EventBridgeEvent,
 			interruptionEventWrappers = append(interruptionEventWrappers, InterruptionEventWrapper{nil, err})
 			continue
 		}
+
+		// Begin drain immediately for scheduled change events to avoid disruptions in cases such as degraded hardware
 		interruptionEvent := monitor.InterruptionEvent{
 			EventID:              fmt.Sprintf("aws-health-scheduled-change-event-%x", event.ID),
 			Kind:                 SQSTerminateKind,
 			AutoScalingGroupName: nodeInfo.AsgName,
-			StartTime:            time.Now(), // begin draining immediately after the notification is processed
+			StartTime:            time.Now(),
 			NodeName:             nodeInfo.Name,
 			InstanceID:           nodeInfo.InstanceID,
 			Description:          fmt.Sprintf("AWS Health scheduled change event received. Instance %s will be interrupted at %s \n", nodeInfo.InstanceID, event.getTime()),

pkg/monitor/sqsevent/sqs-monitor.go

@@ -53,7 +53,7 @@ type SQSMonitor struct {
 	ManagedAsgTag           string
 }
 
-// Convenience wrapper for handling a pair of an interruption event and a related error
+// InterruptionEventWrapper is a convenience wrapper for associating an interruption event with its error, if any
 type InterruptionEventWrapper struct {
 	InterruptionEvent *monitor.InterruptionEvent
 	Err               error
@@ -137,7 +137,7 @@ func (m SQSMonitor) processEventBridgeEvent(eventBridgeEvent *EventBridgeEvent,
 	return append(interruptionEventWrappers, InterruptionEventWrapper{nil, err})
 }
 
-// processInterruptionEvents takes interruption event wrappers and sends interruption events to the passed-in channel
+// processInterruptionEvents takes interruption event wrappers and sends events to the interruption channel
 func (m SQSMonitor) processInterruptionEvents(interruptionEventWrappers []InterruptionEventWrapper, message *sqs.Message) error {
 	dropMessageSuggestionCount := 0
 	failedInterruptionEventsCount := 0