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April 7, 2017 19:07
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Get the list of IP addresses of instances in the same ASG, excluding this instance
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package config | |
import ( | |
"errors" | |
"io/ioutil" | |
"net/http" | |
"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/ec2" | |
) | |
func getASGPeers() ([]string, error) { | |
myInstanceID, err := getOwnInstanceID() | |
if err != nil { | |
return nil, err | |
} | |
return getPeersOfInstance(myInstanceID, session.Options{}) | |
} | |
func getPeersOfInstance(instanceID string, options session.Options) ([]string, error) { | |
sess, err := session.NewSessionWithOptions(options) | |
if err != nil { | |
return nil, err | |
} | |
myASG, err := getASGForInstance(sess, instanceID) | |
if err != nil { | |
return nil, err | |
} | |
instances, err := getInstancesForASG(sess, myASG) | |
if err != nil { | |
return nil, err | |
} | |
instanceIDs := make([]*string, 0, len(instances)) | |
for _, instance := range instances { | |
if *instance.InstanceId != instanceID { | |
instanceIDs = append(instanceIDs, instance.InstanceId) | |
} | |
} | |
return getInstanceIPs(sess, instanceIDs) | |
} | |
func getOwnInstanceID() (string, error) { | |
// Get my instance ID | |
res, err := http.Get("http://169.254.169.254/latest/meta-data/instance-id") | |
if err != nil { | |
return "", err | |
} | |
defer res.Body.Close() | |
myInstanceID, err := ioutil.ReadAll(res.Body) | |
if err != nil { | |
return "", err | |
} | |
return string(myInstanceID), nil | |
} | |
func getASGForInstance(sess *session.Session, instanceID string) (string, error) { | |
svc := autoscaling.New(sess) | |
asgParams := &autoscaling.DescribeAutoScalingInstancesInput{ | |
InstanceIds: []*string{ | |
aws.String(instanceID), | |
}, | |
MaxRecords: aws.Int64(1), | |
} | |
resp, err := svc.DescribeAutoScalingInstances(asgParams) | |
if err != nil { | |
return "", err | |
} | |
if len(resp.AutoScalingInstances) < 1 { | |
return "", err | |
} | |
asgName := resp.AutoScalingInstances[0].AutoScalingGroupName | |
return *asgName, nil | |
} | |
func getInstancesForASG(sess *session.Session, asgName string) ([]*autoscaling.Instance, error) { | |
asgSvc := autoscaling.New(sess) | |
instancesParams := &autoscaling.DescribeAutoScalingGroupsInput{ | |
AutoScalingGroupNames: []*string{ | |
aws.String(asgName), | |
}, | |
MaxRecords: aws.Int64(1), | |
} | |
asgResp, err := asgSvc.DescribeAutoScalingGroups(instancesParams) | |
if err != nil { | |
return nil, err | |
} | |
if len(asgResp.AutoScalingGroups) < 1 { | |
return nil, errors.New("ASG not found: " + asgName) | |
} | |
return asgResp.AutoScalingGroups[0].Instances, nil | |
} | |
func getInstanceIPs(sess *session.Session, instanceIDs []*string) ([]string, error) { | |
ec2Svc := ec2.New(sess) | |
params := &ec2.DescribeInstancesInput{ | |
InstanceIds: instanceIDs, | |
} | |
resp, err := ec2Svc.DescribeInstances(params) | |
if err != nil { | |
return nil, err | |
} | |
ips := make([]string, 0, len(instanceIDs)) | |
for _, resv := range resp.Reservations { | |
for _, resvInstance := range resv.Instances { | |
ips = append(ips, *resvInstance.PrivateIpAddress) | |
} | |
} | |
return ips, nil | |
} |
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