Create snapshots and delete old snapshots

auto_snapshot.py

import boto3
import collections
import logging
import time


ec2 = boto3.client('ec2')
logger = logging.getLogger()
logger.setLevel(logging.INFO)

# lambdaファンクションのエントリーポイント
def lambda_handler(event, context):
    volumes = create_snapshots()
    delete_snapshots(volumes)


def create_snapshots():
    instances = describe_instances([
        {
            'Name': 'tag-key',
            'Values': ['Auto Snapshot']
        },
        {
            'Name': 'tag-value',
            'Values': ['Yes']
        }
    ])

    volumes = {}

    for instance in instances:
        tags = {t['Key']: t['Value'] for t in instance['Tags']}
        generation = int(tags.get('Available Snapshots', 0))

        if generation < 1:
            continue

        for block_device in instance['BlockDeviceMappings']:
            if block_device.get('Ebs') is None:
                continue

            volume_id = block_device['Ebs']['VolumeId']
            description = 'Auto Snapshot ' + '%s (%s)' % (volume_id, instance['RootDeviceName'])

            snapshot = create_snapshot(volume_id, description, [{
                'ResourceType': 'snapshot',
                'Tags': [
                    {
                        'Key': 'Name',
                        'Value': tags['Name'],
                    },
                    {
                        'Key': 'Rotation',
                        'Value': 'Yes',
                    }
                ]
            }])

            logger.info('New snapshot: %s(%s)' % (snapshot['SnapshotId'], description))

            volumes[snapshot['VolumeId']] = generation

    return volumes


def delete_snapshots(volumes):
    auto_snapshots = describe_snapshots(list(volumes.keys()))

    for volume_id, snapshots in list(auto_snapshots.items()):
        num_snapshot = len(snapshots)
        generation = volumes[volume_id]
        delete_count = num_snapshot - generation

        if delete_count <= 0:
            continue

        snapshots.sort(key=lambda x: x['StartTime'])

        outdated_snapshots = snapshots[0:delete_count]

        for snapshot in outdated_snapshots:
            delete_snapshot(snapshot['SnapshotId'])
            logger.info('delete snapshot %s(%s)' % (snapshot['SnapshotId'], snapshot['Description']))


def describe_instances(filters):
    reservations = ec2.describe_instances(Filters=filters)['Reservations']

    return sum([
        [i for i in r['Instances']]
        for r in reservations
    ], [])


def describe_snapshots(volume_ids):
    snapshots = ec2.describe_snapshots(
        Filters=[
            {
                'Name': 'volume-id',
                'Values': volume_ids,
            },
            {
                'Name': 'tag-key',
                'Values': [
                    'Rotation'
                ],
            },
            {
                'Name': 'tag-value',
                'Values': [
                    'Yes'
                ]
            }
        ]
    )['Snapshots']

    snapshot_groups = collections.defaultdict(lambda: [])

    {snapshot_groups[snapshot['VolumeId']].append(snapshot) for snapshot in snapshots}

    return snapshot_groups


def create_snapshot(volume_id, description, tags):
    time.sleep(0.5)
    return ec2.create_snapshot(VolumeId=volume_id, Description=description, TagSpecifications=tags)


def delete_snapshot(snapshot_id):
    time.sleep(0.5)
    return ec2.delete_snapshot(SnapshotId=snapshot_id)