Script for cleaning out old AWS Lambda function versions

clean_lambda_versions.py

#! /usr/bin/env python3

import json
import boto3
import argparse
import time

lambda_client = boto3.client('lambda')

function_choices = [f['FunctionName'] for f in lambda_client.list_functions()['Functions']]

parser = argparse.ArgumentParser(description="Delete a percentage of old lambda function versions")
parser.add_argument('function_name', choices=function_choices, help="Name of lambda function in AWS")
parser.add_argument('--percent', type=float, default=50, help="What percentage of old function versions to delete. Defaults to 50")
args = parser.parse_args()

percent_to_delete = args.percent/100

def get_versions(versions=None, next_marker=None):
    versions = versions or []
    kwargs = {'FunctionName': args.function_name,
              'MaxItems': 50}  # 50 is the max allowed?
    if next_marker:
        kwargs['Marker'] = next_marker
    result = lambda_client.list_versions_by_function(**kwargs)
    versions += result['Versions']
    next_marker = result.get('NextMarker')
    if next_marker:
        versions = get_versions(versions, next_marker)
    return versions

print("Fetching all function versions")
versions = get_versions()
versions = sorted(versions, key=lambda ver: ver['LastModified'])

print("Ignoring the latest version")
for i, version in enumerate(versions):
    if version['Version'] == '$LATEST':
        versions.pop(i)

json.dump(versions, open('lambda_versions.json', 'w'), indent=2)

code_size = 0
for version in versions:
    code_size += version['CodeSize']
total_mb = '{:,.0f}'.format(code_size * 0.000001)

print(f"There are {len(versions)} versions of function '{args.function_name}', totalling {total_mb} MB")

num_to_delete = int(len(versions) * percent_to_delete)
if num_to_delete < 10:
    # Keep 10 at the least
    num_to_delete = 0

print(f"About to delete {num_to_delete} out of {len(versions)} oldest versions ")
time.sleep(10)

for i, version in enumerate(versions[:num_to_delete]):
    print(f"Deleting {i} of {num_to_delete}: {version['LastModified']}")
    lambda_client.delete_function(
                FunctionName=args.function_name,
                Qualifier=version['Version'])