asg-route53

This was written primarily for CoreOS Etcd instances created as part of an AWS Autoscaling Group, using the method described at https://github.com/MonsantoCo/etcd-aws-cluster.

Rather than adding the etcd-aws-cluster unit to every proxy client of your etcd cluster, asg-route53 will add a SRV record to DNS for all the etcd hosts, so they can be discovered by proxy clients, as described at https://coreos.com/etcd/docs/latest/clustering.html#discovery.

How does it work?

• Looks up instance metadata and queries aws-sdk for autoscaling group.
• Looks up all instances for this autoscaling group.
• Updates given DNS record in Route53 to contain all ASG instances.

Usage

docker pull rlister/asg-route53:latest
docker run rlister/asg-route53:latest _etcd-server._tcp.example.com

IAM policy required

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "route53:ChangeResourceRecordSets"
            ],
            "Resource": "arn:aws:route53:::hostedzone/$zone_id",
            "Effect": "Allow"
        },
        {
            "Action": [
                "route53:GetChange"
            ],
            "Resource": "arn:aws:route53:::change/*",
            "Effect": "Allow"
        },
        {
            "Action": [
                "route53:ListHostedZonesByName"
            ],
            "Resource": "*",
            "Effect": "Allow"
        },
        {
            "Action": [
                "autoscaling:DescribeAutoScalingGroups",
                "ec2:DescribeInstances",
                "ec2:DescribeTags"
            ],
            "Resource": "*",
            "Effect": "Allow"
        }
    ]
}

Installation

Binaries for linux and OSX

Download a static binary from https://github.com/rlister/asg-route53/releases.

Docker

docker pull rlister/asg-route53:latest

Unless running under an IAM role, you will need to pass in your AWS credentials to make AWS changes, for example:

docker run \
  -e AWS_REGION \
  -e AWS_ACCESS_KEY_ID \
  -e AWS_SECRET_ACCESS_KEY \
  rlister/asg-route53 my-security-group

Build from source

Build your own using your favourite go build command, for example:

go build ./asg-route53.go

Making a new release

Binaries in releases are built using goxc:

goxc -t    # first use
goxc bump
goxc -bc="linux darwin"

Docker image

I build a tiny docker image from scratch as follows:

version=0.0.1
CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo asg-route53.go
docker build -t rlister/asg-route53:${version} .
docker tag -f rlister/asg-route53:${version} rlister/asg-route53:latest
docker push rlister/asg-route53