Merge pull request #2 from gagliardetto/master

Add minimal autoscaling tools

autoscaling.go

@@ -0,0 +1,116 @@
+package awsutil
+
+import (
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/autoscaling/autoscalingiface"
+
+	"fmt"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/autoscaling"
+	"github.com/aws/aws-sdk-go/service/ec2/ec2iface"
+	// "github.com/y0ssar1an/q"
+	"strings"
+)
+
+// AutoScalingUtil wraps the AWS AutoScaling SDK API and provides additional utilities
+type AutoScalingUtil struct {
+	asgAPI autoscalingiface.AutoScalingAPI
+	ec2Api ec2iface.EC2API
+}
+
+// NewAutoScalingUtilFromRegion creates a AutoScalingUtil from a region
+func NewAutoScalingUtilFromRegion(region string) (*AutoScalingUtil, error) {
+
+	session, err := session.NewSession()
+	if err != nil {
+		return nil, err
+	}
+
+	asgAPI := newAutoScalingAPI(session, region)
+	ec2Api := newEC2API(session, region)
+
+	return NewAutoScalingUtil(asgAPI, ec2Api)
+
+}
+
+// NewAutoScalingUtil creates a AutoScalingUtil given the underlying AWS api implementations (or mocks)
+func NewAutoScalingUtil(asgAPI autoscalingiface.AutoScalingAPI, ec2Api ec2iface.EC2API) (*AutoScalingUtil, error) {
+
+	cnfUtil := &AutoScalingUtil{
+		asgAPI: asgAPI,
+		ec2Api: ec2Api,
+	}
+
+	return cnfUtil, nil
+
+}
+
+// InAutoScaling checks whether the given instance id is part of an
+// AutoScaling group. If it is, it returns a nil error and the asgName.
+func (cfnu AutoScalingUtil) InAutoScaling(instanceId string) (in bool, asgName string, err error) {
+
+	params := &autoscaling.DescribeAutoScalingInstancesInput{
+		InstanceIds: []*string{
+			aws.String(instanceId), // Required
+		},
+	}
+	dsrOutput, err := cfnu.asgAPI.DescribeAutoScalingInstances(params)
+	if err != nil {
+
+		// if we get a "does not exist" then just absorb the error and don't treat it as an error condition
+		// since it's expected if the instance ID is not present in any autoscaling groups
+		if strings.Contains(err.Error(), "does not exist") {
+			return false, "", nil
+		}
+
+		// it's an unexpected error, let's return it to the caller to bring to attention
+		return false, "", err
+
+	}
+	if len(dsrOutput.AutoScalingInstances) == 0 {
+		return false, "", nil
+	}
+
+	asgResource := dsrOutput.AutoScalingInstances[0]
+
+	if asgResource.AutoScalingGroupName == nil {
+		return false, "", fmt.Errorf("asgResource is missing AutoScalingGroupName: %+v", *asgResource)
+	}
+
+	return true, *asgResource.AutoScalingGroupName, nil
+}
+
+// ASG_ARN_fromName returns the ARN of an autoscaling group given its name
+func (cfnu AutoScalingUtil) ASG_ARN_fromName(asgName string) (asgARN string, err error) {
+
+	params := &autoscaling.DescribeAutoScalingGroupsInput{
+		AutoScalingGroupNames: []*string{
+			aws.String(asgName), // Required
+		},
+	}
+	dsrOutput, err := cfnu.asgAPI.DescribeAutoScalingGroups(params)
+	if err != nil {
+
+		// if we get a "does not exist" then just absorb the error and don't treat it as an error condition
+		// since it's expected if the instance ID is not present in any autoscaling groups
+		if strings.Contains(err.Error(), "does not exist") {
+			return "", nil
+		}
+
+		// it's an unexpected error, let's return it to the caller to bring to attention
+		return "", err
+
+	}
+	if len(dsrOutput.AutoScalingGroups) == 0 {
+		return "", nil
+	}
+
+	asgGroup := dsrOutput.AutoScalingGroups[0]
+
+	if asgGroup.AutoScalingGroupARN == nil {
+		return "", fmt.Errorf("asgGroup is missing AutoScalingGroupARN: %+v", *asgGroup)
+	}
+
+	return *asgGroup.AutoScalingGroupARN, nil
+}

aws_api.go

@@ -3,9 +3,10 @@ package awsutil
 import (
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/autoscaling"
 	"github.com/aws/aws-sdk-go/service/cloudformation"
-	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/aws/aws-sdk-go/service/cloudwatch"
+	"github.com/aws/aws-sdk-go/service/ec2"
 )
 
 func newCloudformationAPI(session *session.Session, region string) *cloudformation.CloudFormation {
@@ -40,3 +41,14 @@ func newCloudwatchAPI(session *session.Session, region string) *cloudwatch.Cloud
 	return cw
 
 }
+
+func newAutoScalingAPI(session *session.Session, region string) *autoscaling.AutoScaling {
+
+	as := autoscaling.New(session,
+		&aws.Config{
+			Region: aws.String(region),
+		},
+	)
+	return as
+
+}