gistfile1.txt

import boto3
import collections
import datetime

ec = boto3.client('ec2')

def lambda_handler(event, context):
    reservations = ec.describe_instances().get(
        'Reservations', []
    )

    instances = sum(
        [
            [i for i in r['Instances']]
            for r in reservations
        ], [])
    instances = [i for i in instances if 'NoBackup' not in [t.get('Key') for t in i['Tags']]]
    print "Found %d instances that need backing up" % len(instances)

    to_tag = collections.defaultdict(list)

    for instance in instances:
        try:
            retention_days = [
                int(t.get('Value')) for t in instance['Tags']
                if t['Key'] == 'Retention'][0]
        except IndexError:
            retention_days = 7

        for dev in instance['BlockDeviceMappings']:
            if dev.get('Ebs', None) is None:
                continue
            vol_id = dev['Ebs']['VolumeId']
            print "Found EBS volume %s on instance %s" % (
                vol_id, instance['InstanceId'])

            snap = ec.create_snapshot(
                VolumeId=vol_id,
            )
            try:
                instance_name = [
                    t.get('Value') for t in instance['Tags']
                    if t['Key'] == 'Name'][0]
            except IndexError:
                instance_name = 'unknown'
            
            ec.create_tags(
                Resources=[snap['SnapshotId']],
                Tags=[{'Key': 'ParentInstance', 'Value': instance['InstanceId']},
                      {'Key': 'ParentInstanceName', 'Value': instance_name},
                      {'Key': 'MountPoint', 'Value': dev['DeviceName']}]
            )

            to_tag[retention_days].append(snap['SnapshotId'])

            print "Retaining snapshot %s of volume %s from instance %s for %d days" % (
                snap['SnapshotId'],
                vol_id,
                instance['InstanceId'],
                retention_days,
            )


    for retention_days in to_tag.keys():
        delete_date = datetime.date.today() + datetime.timedelta(days=retention_days)
        delete_fmt = delete_date.strftime('%Y-%m-%d')
        print "Will delete %d snapshots on %s" % (len(to_tag[retention_days]), delete_fmt)
        ec.create_tags(
            Resources=to_tag[retention_days],
            Tags=[
                {'Key': 'DeleteOn', 'Value': delete_fmt},
            ]
        )