Immutable Architecture

• It refers to a system where virtual instances are “disposable”
• once you instantiate infrastructure and code, you never change the instance
• Essence is disposable infrastructure
• It enables
  • infrastructure never strays from its initial “known-good” state
  • operations are simplified
  • “failure” is a routine and continuous way of doing business
• requires full automation of the environment involving
  • resource provisioning
  • bootstrapping
  • package installation
  • code deployment
• Use Elastic Beanstalk in AWS

To enable immutable updates (console) in Elastic Beanstalk

• Open the Elastic Beanstalk console.
• Navigate to the management page for your environment.
• Choose Configuration.
• In the Rolling updates and deployments configuration category, choose Modify.
• In the Configuration Updates section, set Rolling update type to Immutable.

Immutable server pattern

• It makes use of disposable components
• For everything that makes up an application that is not data.
• Hence, once application is deployed, nothing changes on the server
• The packaged code and any deploy scripts is essentially baked into server.
• No outside process is able to modify the contents after the server has been deployed.
• For example, with Docker containers to deploy code, all resource needed will be in the Docker image, which is used to create and run a container.