auto-increment ALB ListenerRule priority

issue-rule-priority

#!/usr/bin/python

import boto3
import sys
import os
from operator import itemgetter


def main(listener_arn):
    client = boto3.client('elbv2')

    rules = client.describe_rules(
        ListenerArn=listener_arn,
    )['Rules']

    rules = [rule for rule in rules if rule['Priority'].isdigit()]

    if not rules:
        return 1

    sorted_rules = sorted(rules, key=lambda x: int(x['Priority']), reverse=True)
    priority = int(sorted_rules[0]['Priority'])+1

    return priority


if __name__ == '__main__':
    try:
        if len(sys.argv) < 2:
            raise Exception('usage "{} arn:aws:elasticloadbalancing:us-west-2:123456789123:listener/app/alb/xxxxxxxxxx/yyyyyyyyyyy"'.format(os.path.basename(__file__)))
        print main(sys.argv[1])
        exit(0)
    except Exception as e:
        print "Error: {}".format(str(e))
        exit(1)