Stop_EC2.py

import boto3
import json
client = boto3.client('ec2')

def lambda_handler(event, context):
    print 'Start Lambda function(StopEC2 by Tag)'

    detail = event['detail']
    instance_id = detail['instance-id']
    
    if instance_id is None:
        print 'There is no Instance ID'
        return 'false'

    # Show Instance ID/state        
    print "Check start Target instance ID =" + instance_id
    print 'State= '+ str(detail['state'])

    if  detail['state'] != 'pending':
        return "Status fail"
    
    # Exec descibeinstances by instance-id
    # About boto ec2.describe-instaces check below link
    # http://boto3.readthedocs.org/en/latest/reference/services/ec2.html#EC2.Client.describe_instances
    res_json = client.describe_instances(
        DryRun = False,
        Filters=[{'Name':'instance-id', 'Values':[instance_id]}]
        )
    HTTP_code = res_json['ResponseMetadata']['HTTPStatusCode']
    if str(HTTP_code) != '200':
        print 'describe instances command fail: HTTP responce=' + str(HTTP_code)

    res = res_json['Reservations'].pop()
    Instance_info = res['Instances'].pop()
    
    #Tag check
    if check_Tags(Instance_info, instance_id) == 'true':
        return 'Tags are Okay'
    else:
        return 'Need to Setup the mandatory key'
    
    context.done('end of Lambda')

# Check Tag key
#   Input:Tags [associative array]
#   Output:true/false
def check_Tags(Instance_info, instance_id):
    
    #defined
    MANDATORY_KEYNAME='Cost'

    if Instance_info.has_key('Tags'):
        tags = Instance_info['Tags']
    else:
        exec_stop_Instance(instance_id)
        return

    for tag in tags:
        print tag.get('Key')
        if tag.get('Key') == MANDATORY_KEYNAME:
            return 'true'
            
    exec_stop_Instance(instance_id)
    return 'false'

# Execute EC2 stop
#   Input: Instance-ID
#   Output: none
def exec_stop_Instance(instance_id):
    print 'There is no Mandatory Tag'
    print 'Instance Stop :' + instance_id

    # See datail:http://boto3.readthedocs.org/en/latest/reference/services/ec2.html#EC2.Client.stop_instances
    ret = client.stop_instances(
        DryRun=False,
        InstanceIds=[instance_id]
        )
        
    print 'Execute Instance Stop'
    return