This Docker container allows you to (de)register an EC2 instance with an Amazon Elastic Load Balancer (ELB).

The elb-presence container takes all of its configuration from environment variables.

docker run --rm --name example-presence -e AWS_ACCESS_KEY=AKIAIBC5MW3ONCW6J2XQ -e AWS_SECRET_KEY=qxB5k7GhwZNweuRleclFGcvsqGnjVvObW5ZMKb2V -e AWS_REGION=us-east-1 -e ELB_NAME=ExampleLoadBalancer quay.io/coreos/elb-presence

• AWS_ACCESS_KEY ... Your AWS access key
• AWS_SECRET_KEY ... Your AWS secret key
• AWS_REGION ... The AWS region that your load balancer is located in
• ELB_NAME ... The exact name of your load balancer

You can omit the AWS_ACCESS_KEY and AWS_SECRET_KEY variables and fallback to an instance IAM role for authentication.

Usually you'll want to manage the lifecycle of your presence service using fleet. To do so, you can create a service file similar to this example:

[email protected]

[Unit]
Description=Example Presence Service
BindsTo=my-service@%i.service

[Service]
TimeoutStartSec=0
ExecStartPre=-/usr/bin/docker kill %p-%i
ExecStartPre=-/usr/bin/docker rm %p-%i
ExecStartPre=/usr/bin/docker pull quay.io/coreos/elb-presence:latest
ExecStart=/usr/bin/docker run --rm --name %p-%i -e AWS_ACCESS_KEY=AKIAIBC5MW3ONCW6J2XQ -e AWS_SECRET_KEY=qxB5k7GhwZNweuRleclFGcvsqGnjVvObW5ZMKb2V -e AWS_REGION=us-east-1 -e ELB_NAME=ExampleLoadBalancer quay.io/coreos/elb-presence
ExecStop=/usr/bin/docker stop %p-%i

[X-Fleet]
MachineOf=my-service@%i.service

This service will deploy to the same machine as your service (MachineOf) and automatically start and stop along with it (BindsTo).

If you want to create a minimum privilege IAM user for this presence service, here is an example IAM Inline Policy for you to use.

Note that you will have to replace the arn:... URN with your loadbalancer's.

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": [
      "elasticloadbalancing:DeregisterInstancesFromLoadBalancer",
      "elasticloadbalancing:RegisterInstancesWithLoadBalancer"
    ],
    "Resource": "arn:aws:elasticloadbalancing:us-west-1:001340051967:loadbalancer/ExampleLoadBalancer"
  }]
}