def global_table_update()

in source/cfn-global-table/cfn-global-table.py [0:0]

• 44 lines of code
• 10 McCabe index (conditional complexity)

def global_table_update(event, context):
    logger.debug(json.dumps(event))
    global_table_name = event['ResourceProperties']['GlobalTableName']

    try:
        resp = {'Status': 'FAILED', 'Data': {'GlobalTableName': global_table_name, 'LogGroup': context.log_group_name }}
        client = boto3.client('dynamodb')

        # Describe the existing global table, as we cannot trust the provided
        # event['OldResourceProperties']['ReplicationGroupList']) to show the
        # current actual replication group list for a stack update failure / rollback.
        response = {}
        response = client.describe_global_table(
            GlobalTableName=global_table_name
        )
        logger.debug(response)

        existing_replication_groups = set() 
        for region in response['GlobalTableDescription']['ReplicationGroup']:
            existing_replication_groups.add(region['RegionName'])

        new_rep_groups = set(event['ResourceProperties']['ReplicationGroupList'])
        old_rep_groups = set(event['OldResourceProperties']['ReplicationGroupList'])

        changeset_rep_group_discrepancies = old_rep_groups - existing_replication_groups
        if len(changeset_rep_group_discrepancies):
            logger.info("Using the results of describe_global_table rather than the value from OldResourceProperties in the event")
            # Use reality, not the value from OldResourceProperties in the event
            old_rep_groups = existing_replication_groups

        if new_rep_groups == old_rep_groups:
            logger.info('No replication group changes detected')
            resp['Reason'] = 'No replication group changes detected'
            resp['Status'] = 'SUCCESS'
            return resp
        else:
            logger.info('Replication group changes detected. Updating Global Table')

        AddReplicationGroups = new_rep_groups - old_rep_groups
        RemoveReplicationGroups = old_rep_groups - new_rep_groups

        if len(AddReplicationGroups):
            for region in AddReplicationGroups:
                update_global_table(global_table_name, region, 'Create')
                logger.info('Add replication group region: ' + region)

        if len(RemoveReplicationGroups):
            for region in RemoveReplicationGroups:
                update_global_table(global_table_name, region, 'Delete')
                logger.info('Remove replication group region: ' + region)

        resp['Reason'] = 'Updated Global Table: ' + global_table_name
        resp['Status'] = 'SUCCESS'
    except Exception as e:
        logger.error('Failed to update DynamoDB Global Table: ' + global_table_name)
        resp['Reason'] = 'Failed to update Global Table: ' + e.message
        resp['Status'] = 'FAILED'
    
    return resp