Set last scale in and out event on autoscaler activity

lambda/main.go

@@ -141,7 +141,20 @@ func Handler(ctx context.Context, evt json.RawMessage) (string, error) {
 			}
 
 			client := buildkite.NewClient(token)
-
+			asg := &scaler.ASGDriver{
+				Name: mustGetEnv(`ASG_NAME`),
+				Sess: sess,
+			}
+			scaleOutOutput, scaleInOutput, err := asg.GetLastScalingInAndOutActivity()
+			if err != nil {
+				log.Printf("Failed to get last scale in and out activity because %s", err)
+			}
+			if scaleInOutput != nil {
+				lastScaleIn = *scaleInOutput.StartTime
+			}
+			if scaleOutOutput != nil {
+				lastScaleOut = *scaleOutOutput.StartTime
+			}
 			params := scaler.Params{
 				BuildkiteQueue:       mustGetEnv(`BUILDKITE_QUEUE`),
 				AutoScalingGroupName: mustGetEnv(`ASG_NAME`),

scaler/asg.go

@@ -10,25 +10,30 @@ import (
 	"github.com/aws/aws-sdk-go/service/autoscaling"
 )
 
+const (
+	activitySucessfulStatusCode = "Successful"
+	userRequestForChangingDesiredCapacity = "a user request explicitly set group desired capacity changing the desired capacity"
+)
+
 type AutoscaleGroupDetails struct {
 	Pending      int64
 	DesiredCount int64
 	MinSize      int64
 	MaxSize      int64
 }
 
-type asgDriver struct {
-	name string
-	sess *session.Session
+type ASGDriver struct {
+	Name string
+	Sess *session.Session
 }
 
-func (a *asgDriver) Describe() (AutoscaleGroupDetails, error) {
-	log.Printf("Collecting AutoScaling details for ASG %q", a.name)
+func (a *ASGDriver) Describe() (AutoscaleGroupDetails, error) {
+	log.Printf("Collecting AutoScaling details for ASG %q", a.Name)
 
-	svc := autoscaling.New(a.sess)
+	svc := autoscaling.New(a.Sess)
 	input := &autoscaling.DescribeAutoScalingGroupsInput{
 		AutoScalingGroupNames: []*string{
-			aws.String(a.name),
+			aws.String(a.Name),
 		},
 	}
 
@@ -64,10 +69,10 @@ func (a *asgDriver) Describe() (AutoscaleGroupDetails, error) {
 	return details, nil
 }
 
-func (a *asgDriver) SetDesiredCapacity(count int64) error {
-	svc := autoscaling.New(a.sess)
+func (a *ASGDriver) SetDesiredCapacity(count int64) error {
+	svc := autoscaling.New(a.Sess)
 	input := &autoscaling.SetDesiredCapacityInput{
-		AutoScalingGroupName: aws.String(a.name),
+		AutoScalingGroupName: aws.String(a.Name),
 		DesiredCapacity:      aws.Int64(count),
 		HonorCooldown:        aws.Bool(false),
 	}
@@ -80,6 +85,50 @@ func (a *asgDriver) SetDesiredCapacity(count int64) error {
 	return nil
 }
 
+func (a *ASGDriver) GetAutoscalingActivities(nextToken *string) (*autoscaling.DescribeScalingActivitiesOutput, error) {
+	svc := autoscaling.New(a.Sess)
+	input := &autoscaling.DescribeScalingActivitiesInput{
+		AutoScalingGroupName: aws.String(a.Name),
+		NextToken: nextToken,
+	}
+	return svc.DescribeScalingActivities(input)
+}
+
+func (a *ASGDriver) GetLastScalingInAndOutActivity() (*autoscaling.Activity, *autoscaling.Activity, error) {
+	const scalingOutKey = "increasing the capacity"
+	const shrinkingKey = "shrinking the capacity"
+	var nextToken *string
+	var lastScalingOutActivity *autoscaling.Activity
+	var lastScalingInActivity *autoscaling.Activity
+	hasFoundScalingActivities := false
+	for !hasFoundScalingActivities {
+		output, err := a.GetAutoscalingActivities(nextToken)
+		if err != nil {
+			return nil, nil, err
+		}
+		for _, activity := range output.Activities {
+			// Filter for successful activity and explicit desired count changes
+			if *activity.StatusCode == activitySucessfulStatusCode &&
+				strings.Contains(*activity.Cause, userRequestForChangingDesiredCapacity) {
+				if lastScalingOutActivity == nil && strings.Contains(*activity.Cause, scalingOutKey) {
+					lastScalingOutActivity = activity
+				} else if lastScalingInActivity == nil && strings.Contains(*activity.Cause, shrinkingKey) {
+					lastScalingInActivity = activity
+				}
+			}
+			if lastScalingOutActivity != nil && lastScalingInActivity != nil {
+				hasFoundScalingActivities = true
+				break
+			}
+		}
+		nextToken = output.NextToken
+		if nextToken == nil {
+			break
+		}
+	}
+	return lastScalingOutActivity, lastScalingInActivity, nil
+}
+
 type dryRunASG struct {
 }
 

scaler/scaler.go

@@ -67,9 +67,9 @@ func NewScaler(client *buildkite.Client, sess *session.Session, params Params) (
 			scaler.metrics = &dryRunMetricsPublisher{}
 		}
 	} else {
-		scaler.autoscaling = &asgDriver{
-			name: params.AutoScalingGroupName,
-			sess: sess,
+		scaler.autoscaling = &ASGDriver{
+			Name: params.AutoScalingGroupName,
+			Sess: sess,
 		}
 
 		if params.PublishCloudWatchMetrics {