Example of setting up AWS auto scaling using boto API

autoscaling_boto.py

"""
The MIT License (MIT)
Copyright (c) 2011 Numan Sachwani

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"""
import boto.ec2

from boto.ec2.elb import ELBConnection
from boto.ec2.elb import HealthCheck

from boto.ec2.autoscale import AutoScaleConnection
from boto.ec2.autoscale import LaunchConfiguration
from boto.ec2.autoscale import AutoScalingGroup
from boto.ec2.autoscale import ScalingPolicy

##############################CONFIGURATION#######################################
"""
This section is for configuring the rest of the script.
This script will do 3 things:
1. Setup a new Elastic Load Balancer
2. Create an Auto Scaling Group and configure it with an Launch Configuration
3. Create Policies for Scaling Up and Scaling Down
"""
AWS_ACCESS_KEY = '' #Your access key
AWS_SECRET_KEY = '' #Your secret key

region = 'us-east-1' #The region you want to connect to

elastic_load_balancer = {
    'name': 'my-lb',#The name of your load balancer
    'health_check_target': 'HTTP:80/index.html',#Location to perform health checks
    'connection_forwarding': [(80, 80, 'http'), (443, 443, 'tcp')],#[Load Balancer Port, EC2 Instance Port, Protocol]
    'timeout': 3, #Number of seconds to wait for a response from a ping
    'interval': 20 #Number of seconds between health checks
}

autoscaling_group = {
    'name': 'my-autoscaling-group',#descriptive name for your auto scaling group
    'min_size': 1,#Minimum number of instances that should be running at all times
    'max_size': 1 #Maximum number of instances that should be running at all times

}

lc_name = 'my-launch-config' #Descriptive name for your launch configuration

#=================AMI to launch======================================================
as_ami = {
    'id': 'ami-8e1fece7', #The AMI ID of the instance your Auto Scaling group will launch
    'access_key': 'as-ami-ec2key', #The key the EC2 instance will be configured with
    'security_groups': ['as-ami-webserver'], #The security group(s) your instances will belong to
    'instance_type': 't1.micro', #The size of instance that will be launched
    'instance_monitoring': True #Indicated whether the instances will be launched with detailed monitoring enabled. Needed to enable CloudWatch
}

##############################END CONFIGURATION#######################################

#=================Construct a list of all availability zones for your region=========
conn_reg = boto.ec2.connect_to_region(region_name=region)
zones = conn_reg.get_all_zones()

zoneStrings = []
for zone in zones:
    zoneStrings.append(zone.name)


conn_elb = ELBConnection(AWS_ACCESS_KEY, AWS_SECRET_KEY)
conn_as = AutoScaleConnection(AWS_ACCESS_KEY, AWS_SECRET_KEY)

#=================Create a Load Balancer=============================================
#For a complete list of options see http://boto.cloudhackers.com/ref/ec2.html#module-boto.ec2.elb.healthcheck
hc = HealthCheck('healthCheck',
                     interval=elastic_load_balancer['interval'],
                     target=elastic_load_balancer['health_check_target'],
                     timeout=elastic_load_balancer['timeout'])

#For a complete list of options see http://boto.cloudhackers.com/ref/ec2.html#boto.ec2.elb.ELBConnection.create_load_balancer
lb = conn_elb.create_load_balancer(elastic_load_balancer['name'],
                                       zoneStrings,
                                       elastic_load_balancer['connection_forwarding'])

lb.configure_health_check(hc)

#DNS name for your new load balancer
print "Map the CNAME of your website to: %s" % (lb.dns_name)

#=================Create a Auto Scaling Group and a Launch Configuration=============================================
#For a complete list of options see http://boto.cloudhackers.com/ref/ec2.html#boto.ec2.autoscale.launchconfig.LaunchConfiguration
lc = LaunchConfiguration(name=lc_name, image_id=as_ami['id'],
                             key_name=as_ami['access_key'],
                             security_groups=as_ami['security_groups'],
                             instance_type=as_ami['instance_type'],
                             instance_monitoring=as_ami['instance_monitoring'])
conn_as.create_launch_configuration(lc)

#For a complete list of options see http://boto.cloudhackers.com/ref/ec2.html#boto.ec2.autoscale.group.AutoScalingGroup
ag = AutoScalingGroup(group_name=autoscaling_group['name'], load_balancers=[elastic_load_balancer['name']],
                          availability_zones=zoneStrings,
                          launch_config=lc, min_size=autoscaling_group['min_size'], max_size=autoscaling_group['max_size'])
conn_as.create_auto_scaling_group(ag)


#=================Create Scaling Policies=============================================
#Policy for scaling the number of servers up and down
#For a complete list of options see http://boto.cloudhackers.com/ref/ec2.html#boto.ec2.autoscale.policy.ScalingPolicy
scalingUpPolicy = ScalingPolicy(name='webserverScaleUpPolicy',
                                              adjustment_type='ChangeInCapacity',
                                              as_name=ag.name,
                                              scaling_adjustment=2,
                                              cooldown=180)

scalingDownPolicy = ScalingPolicy(name='webserverScaleDownPolicy',
                                              adjustment_type='ChangeInCapacity',
                                              as_name=ag.name,
                                              scaling_adjustment=-1,
                                              cooldown=180)

conn_as.create_scaling_policy(scalingUpPolicy)
conn_as.create_scaling_policy(scalingDownPolicy)

Shouldn't you also specify the region to connect to in AutoScaleConnection(AWS_ACCESS_KEY, AWS_SECRET_KEY)? It looks like it works now because the default region is 'us-east-1', which also happens to be the region you want to use

Hello,
How to get running instance ID and [ami id ]