associate elastic ip for ec2 instances

associate_elastic_ip.py

#!/usr/bin/python36
import boto3
import requests
import os


def ec2_associate_eip(aws_instance, region_name, tag_name, tag_value):
    client = boto3.client('ec2', region_name=region_name)
    eip_list = client.describe_addresses(Filters=[{'Name': f'tag:{tag_name}', 'Values': [tag_value]}])
    free_eips = []
    if 'Addresses' in eip_list:
        for eip_list in eip_list['Addresses']:
            if 'InstanceId' in eip_list:
                if eip_list['InstanceId']:
                    continue
            free_eips.append(eip_list['PublicIp'])
    else:
        print('Could not retrieve elastic ip list')
        exit(0)
    if free_eips:
        associate_eip = client.associate_address(PublicIp=free_eips[0], InstanceId=aws_instance)
        if associate_eip['AssociationId']:
            return 'EIP {} associated to {}'.format(free_eips[0], aws_instance)
        else:
            return 'Could not associate elastic ip'
    else:
        return 'Could not retrieve elastic ip'


def ec2_metadata(param):
    try:
        response = requests.get(f'http://169.254.169.254/latest/meta-data/{param}')
        if response.ok:
            return response.text
        else:
            return ''
    except Exception as e:
        print(str(e))
        return ''


if __name__ == '__main__':
    eip_tag_name = os.environ['EIP_TAG']
    eip_tag_value = os.environ['EIP_TAG_VALUE']
    instance_id = ec2_metadata('instance-id')
    region = ec2_metadata('placement/availability-zone')[:-1]
    if instance_id and region:
        print(ec2_associate_eip(instance_id, region, eip_tag_name, eip_tag_value))