Signal an AWS Auto Scaling Group that an instance has come into service within an ELB.

signaler.sh

#!/bin/bash

# Dependencies 
#  - awscli
#  - jq

# Needed IAM permissions 
#  - elasticloadbalancing:DescribeInstanceHealth
#  - elasticloadbalancing:DescribeLoadBalancers
#  - autoscaling:DescribeAutoScalingGroups

STACK_NAME="STACK NAME"
INSTANCE_ID=$(curl -s http://instance-data/latest/meta-data/instance-id)
REGION=$(curl -s http://instance-data/latest/dynamic/instance-identity/document | jq .region -r)
ELB_NAME=$(aws elb describe-load-balancers --region us-east-1 | jq -r ".LoadBalancerDescriptions[] | select(.Instances[].InstanceId == \"${INSTANCE_ID}\") | .LoadBalancerName")
ASG_NAME=$(aws autoscaling describe-auto-scaling-groups --region us-east-1 | jq -r ".AutoScalingGroups[] | select(.Instances[].InstanceId == \"${INSTANCE_ID}\") | .AutoScalingGroupName")

while sleep 1; do
	STATE=$(aws elb describe-instance-health --region ${REGION} --load-balancer-name ${ELB_NAME} | jq --raw-output ".InstanceStates[] | select(.InstanceId == \"${INSTANCE_ID}\") | .State")
	if [ $STATE == "InService" ]
	then
		break
	fi
done

/opt/aws/bin/cfn-signal \
	--success true \
	--stack    ${STACK_NAME} \
	--resource ${ASG_NAME} \
	--region   ${REGION}