aws-ha-updater

This project is DEPRECATED and not any longer supported

The aws-ha-updater allows you to update AWS Cloudformation stacks in a highly available manner.

Why another tool?

• Raw CloudFormation would be the preferred solution for rolling out updates, but CloudFormation is currently unable to use the ELB health check to see if an instance with a new launch configuration comes up healthy. The result is that deployment with CloudFormation is a gamble that might result in a cluster of borked instances, which is not acceptable for a web company.

• Asgard, the netflix solution to this, is being rewritten and nobody knows for sure when 2.0 will hit the repository.

• The aws-missing-tools repository provides a bash and ruby implementation. We're not comfortable with using bash to instrument EC2/CFN, and have not evaluated the ruby variant. This solution is however heavily inspired by the aws-ha-release script from the missing-tools collection.

Prerequisites:

• python 2.6+ (but not python3 yet)

• boto SDK

• AWS credentials for boto (e.g. $HOME/.boto file)

• AWS resources managed by CloudFormation, described in templates

• ASGs must not have an UpdatePolicy (we implement our own here)

Usage

update-stack STACK_NAME [options] [PARAMETER...]

Options:
    --region=STRING            aws region to connect to [default: eu-west-1]
    --template=FILENAME or URL

    --warmup-seconds=INT       Seconds to wait for warmup [default: 25]
    --action-timeout=INT       Seconds to wait for the action to finish [default: 300]
    --lenient_look_back=INT    Seconds to look back for events [default: 5]

    PARAMETER...               key=value pairs, must correspond to the template parameters

update-asgs STACK_NAME [options]

Options:
    --region=TEXT   aws region [default: eu-west-1]

Big picture

update-stack

• validate template file when given

• create stack when needed

• update stack and wait for action to complete

• when successful: update asgs

update-asgs

• suspend all autoscaling processes

• double ASG sizes

• wait for ASG to launch new instances

• wait for instances to be "InService" according to ELB

  • when successful: terminate the old instances

  • when timeout occured: terminate the new instances

• reset ASG sizes

• resume all processes (when timeout: disable autoscaling processes)