Manage Systemd Units on AWS CoreOS Tagged Instances with Fabric and boto

fabfile.py

import boto, urllib2
from boto.ec2 import connect_to_region
from fabric.api import env, run, cd, settings, sudo
from fabric.api import parallel
import os
import sys
REGION = os.environ.get("AWS_EC2_REGION")
# Server user
env.user = "core"
# List of AWS private key Files
env.key_filename = ["~/.ssh/key_file.pem"]
# Fabric task to restart systemctl, runs in parallel
# To execute task using fabric run following
# fab set_hosts:Name,AWS_TAGGED_INSTANCE_NAME,us-west-2 restart_systemctl
@parallel
def restart_systemctl(servicefile):
     with cd("/etc/systemd/system"):
          run('sudo systemctl restart %s' % servicefile)
# Fabric task to set env.hosts based on tag key-value pair
def set_hosts(tag = "Name", value="AWS_TAGGED_INSTANCE_NAME", region=REGION):
     key = "tag:"+tag
          env.hosts = _get_public_dns(region, key, value)
# Private method to get public DNS name for instance with given tag key and value pair
def _get_public_dns(region, key, value ="*"):
     public_dns = []
     connection = _create_connection(region)
     reservations = connection.get_all_instances(filters = {key : value})
     for reservation in reservations:
          for instance in reservation.instances:
          print "Instance", instance.public_dns_name
          public_dns.append(str(instance.public_dns_name))
     return public_dns
# Private method for getting AWS connection
def _create_connection(region):
     print "Connecting to ", region
     conn = connect_to_region(
          region_name = region,
          aws_access_key_id=os.environ.get("AWS_ACCESS_KEY_ID"),
          aws_secret_access_key=os.environ.get("AWS_SECRET_ACCESS_KEY")
     )
     print "Connection with AWS established"
     return conn