snapshot lambda

der.py

import boto3
import json
import datetime

def respond(err, res=None):
    return {
        'statusCode': '400' if err else '200',
        'body': err.message if err else json.dumps(res, default=str),
        'headers': {
            'Content-Type': 'application/json',
        },
    }

# these should be separate AWS Lambdas
def create(ebsid, hostname, device, tags):
    ec2 = boto3.client('ec2')
    snapshot = ec2.create_snapshot(
        VolumeId=ebsid,
        Description="%s:%s" % (hostname, device)
    )
    ec2.create_tags(Resources=[snapshot.get('SnapshotId')], Tags=tagfilter(tags))
    return snapshot

def delete(snapshotids):
    ec2 = boto3.client('ec2')
    for i in snapshotids:
        ec2.delete_snapshot(SnapshotId = i)
    return snapshotids

def search(hostname, device):
    ec2 = boto3.client('ec2')
    snapshots = []
    pages = ec2.get_paginator('describe_snapshots').paginate(
        Filters=[{'Name': 'description', 'Values': ["%s:%s" % (hostname, device)]}]
    )
    for page in pages:
        for snap in page['Snapshots']:
                snapshots.append(snap)
    return snapshots
    
def tagfilter(dirtytags = []):
    cleantags = []
    for t in dirtytags:
        if t['Key'][:4] != 'aws:':
            cleantags.append(t)
    return cleantags
            
# event requires hostname, device(default 0), period(no), oldest(no)
def lambda_handler(event, context):
    ec2 = boto3.client('ec2')
    if event.get('hostname') is None:
        return respond(ValueError('hostname is required'))
    result = ec2.describe_instances(
        Filters=[
        {
            'Name': 'tag:Name',
            'Values': [
                event['hostname'],
            ]
        }
    ])
    if len(result['Reservations']) != 1:
        return respond (RuntimeError("no matching hostname"))
    instance = result['Reservations'][0]['Instances'][0]
    tags = instance['Tags']
    devices = sorted(instance['BlockDeviceMappings'], key=lambda d: d['DeviceName'])
    offset = event.get('device', 0)
    ebsid = devices[offset]['Ebs']['VolumeId']

    snapshots = search(event['hostname'], event['device'])
    nowish = datetime.datetime.utcnow()
    oldsnaps = []
    result = {}
    
    for snap in snapshots:
        if (snap['StartTime'].replace(tzinfo=None) > nowish - datetime.timedelta(hours=event['period'])):
            result['SnapshotId'] = snap['SnapshotId']
        if ('oldest' in event) and (snap['StartTime'].replace(tzinfo=None) < nowish - datetime.timedelta(hours=event['oldest'])):
            oldsnaps.append(snap['SnapshotId'])
    if 'SnapshotId' not in result:
        result['SnapshotId'] = create(ebsid, event['hostname'], event['device'], tags).get('SnapshotId')
    result['Deleted'] = delete(oldsnaps)


    # result would be nice to have status of retained snapshots (Completed, In Progress, Failed)
    return respond(None, result)


if __name__ == "__main__":
    import sys
    print lambda_handler(event={
       'hostname': sys.argv[1],
       'device': int(sys.argv[2]),
       'period': int(sys.argv[3]),
       'oldest': int(sys.argv[4])},context=None)