asg-check-n-associate-eip

#!/bin/bash

EIP="$1" # "50.16.123.123"
ASG="$2" # "www"

if [ -z "$EIP" ] || [ -z "$ASG" ]; then
    echo "Usage: $(basename $0) EIP ASG"
    echo "Example: $(basename $0) 50.16.123.123 www"
    exit 1;
fi

insIDbyADDR() {
    aws ec2 describe-addresses --public-ips "$1" \
     | jq -r '.Addresses[] | .InstanceId'
}
insIDsByASG() {
    aws autoscaling describe-auto-scaling-groups --auto-scaling-group-names "$1" \
     | jq -r '.AutoScalingGroups[] | .Instances | map(select(.LifecycleState == "InService"))[]  | .InstanceId'
}

ALLOWED_IDS=$(insIDsByASG $ASG)
FIRST_ALLOWED_ID=$(echo $ALLOWED_IDS | awk '{print $1; exit}')

if [ -z "$FIRST_ALLOWED_ID" ]; then
    echo >&2 "Error: unable to find any allowed IDs... aborting. (EIP:$EIP ASG:$ASG)";
    exit 1;
fi

CURR_ID=$(insIDbyADDR $EIP)
if [ -z "$CURR_ID" ]; then
    echo >&2 "Warn: Elastic IP ($EIP) not associated!"
    echo $FIRST_ALLOWED_ID | xargs -t aws ec2 associate-address --public-ip $EIP --instance-id
else
    OK="no"
    for ALLOWED_ID in $ALLOWED_IDS; do
        if [ "$ALLOWED_ID" = "$CURR_ID" ]; then
            OK="yep"
        fi
    done
    if [ "$OK" = "no" ]; then
        echo >&2 "Warn: Elastic IP ($EIP) associated with wrong instance ($CURR_ID)..."
        echo $FIRST_ALLOWED_ID | xargs -t aws ec2 associate-address --public-ip $EIP --instance-id
    else
        echo "Elastic IP ($EIP) associated with instance ($CURR_ID). fine.. no need to change!"
    fi
fi