At the moment we are only using RDS and ElastiCache within AWS, but more services we use the more maintenance windows is going to come up. Rather than have them at random places around the week and clock, I figure it would be useful to have just a single window that we can subsequently work into our SLAs etc. Now, I really like the management consoles AWS has, but its a lot of clicks to track things — especially if I start using something like CloudFormation and Autoscaling or something to be making things magically.

Scripting to the rescue.

Our applications are PHP based, but at my heart I’m a Python guy, so I whipped up one. And aside from the fear of modifying running items, it appears to have worked well.

<pre lang="python">import boto3

maintenance_window = 'sun:09:35-sun:10:35'

# rds can have maintenance windows
update_rds = False
rds = boto3.client('rds')
paginator = rds.get_paginator('describe_db_instances')
for response_iterator in paginator.paginate():
    print('Current RDS Maintenance Windows')
    for instance in response_iterator['DBInstances']:
        print('%s: %s UTC' % (instance['DBInstanceIdentifier'], instance['PreferredMaintenanceWindow']))
        if instance['PreferredMaintenanceWindow'].lower() != maintenance_window.lower():
            update_rds = True

if update_rds == True:
    paginator = rds.get_paginator('describe_db_instances')
    for response_iterator in paginator.paginate():
        for instance in response_iterator['DBInstances']:
            if instance['PreferredMaintenanceWindow'].lower() != maintenance_window.lower():
                rds.modify_db_instance(
                    DBInstanceIdentifier=instance['DBInstanceIdentifier'],
                    PreferredMaintenanceWindow=maintenance_window
                )
    paginator = rds.get_paginator('describe_db_instances')
    for response_iterator in paginator.paginate():
        print('Adjusted RDS Maintenance Windows')
        for instance in response_iterator['DBInstances']:
            print('%s: %s UTC' % (instance['DBInstanceIdentifier'], instance['PreferredMaintenanceWindow']))

# elasticache can have maintenance windows
update_ec = False
ec = boto3.client('elasticache')
paginator = ec.get_paginator('describe_cache_clusters')
for response_iterator in paginator.paginate():
    print('Current ElastiCache Maintenance Windows')
    for instance in response_iterator['CacheClusters']:
        print('%s: %s UTC' % (instance['CacheClusterId'], instance['PreferredMaintenanceWindow']))
        if instance['PreferredMaintenanceWindow'].lower() != maintenance_window.lower():
            update_ec = True

if update_ec == True:
    paginator = ec.get_paginator('describe_cache_clusters')
    for response_iterator in paginator.paginate():
        for instance in response_iterator['CacheClusters']:
            if instance['PreferredMaintenanceWindow'] != maintenance_window:
                ec.modify_cache_cluster(
                    CacheClusterId=instance['CacheClusterId'],
                    PreferredMaintenanceWindow=maintenance_window
                )

    paginator = ec.get_paginator('describe_cache_clusters')
    for response_iterator in paginator.paginate():
        print('Adjusted ElastiCache Maintenance Windows')
        for instance in response_iterator['CacheClusters']:
            print('%s: %s UTC' % (instance['CacheClusterId'], instance['PreferredMaintenanceWindow']))