> For the complete documentation index, see [llms.txt](https://ysfang82.gitbook.io/development-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ysfang82.gitbook.io/development-notes/aws-notes/service/deployment/elastic-beanstalk.md).

# Elastic Beanstalk

Introduction

* Providing application code / Git Repo, scalable application / RDS to deploy onto AWS.
* Managed service:
  * Instance configuration / OS is handled by Beanstalk
  * Deployment strategy is configurable but performed by Elastic Beanstalk
* Good to re-platform your application from on-premise to the cloud
* Only pay for the instances used

Feature

* Supports:
  * Go
  * Java SE / Tomcat
  * .Net on Windows Server with IIS
  * Node.js
  * PHP
  * Python
  * Ruby
  * Packer Builder
  * Docker (Single container / multiconainer / preconfigured )
  * Can write your custom plaform (advanced)
* Architecture model:
  * Single Instance: good for dev
  * LB + ASG: good for production or pre-production apps
  * ASG only: good for non-web apps in production
* Deployment policy:
  * All at once
  * Rolling (reduce capacity then fill back with new service) 
    * Deploy the new version in batches. Each batch is taken out of service during the deployment phase, reducing your environment's capacity by the number of instances in a batch.
  * Rolling with additional batch (provision new service then terminate old one)
    * Deploy the new version in batches, but first launch a new batch of instances to ensure full capacity during the deployment process.
  * Immutable
    * Deploy the new version to a fresh group of instances by performing an immutable update.
  * Traffic splitting
    * Deploy the new version to a fresh group of instances and temporarily split incoming client traffic between the existing application version and the new one.
* Replacement Options for Configuration changes:
  * Rolling
    * prevents downtime, applies changes in batches, keeping a minimum number of instances running and serving traffic at all times.
  * Immutable
    * Launches a temporary ASG outside of your environment with a separate set of instances running with the new configuration. 
    * Then places the new instances behind your load balancer. Old and new instances both serve traffic until the new instances pass health checks. 
    * Then moves the new instances into your ASG and terminates the temporary group and old instances.
  * Disabled (like all at once)
    * Makes no attempt to avoid downtime. It terminates old instances and replaces them with new ones.
* Scenarios
  * Decoupling Web Server, Woker Servers with SQS
    * If a service contains web tier and worker tier, can decouple them by SQS.
  * Blue / Green Deployment
    * Create a new "stage" environment for deploying v2 there
    * Route swapping options:
      * Utilize Route53 with weighted policies
      * Use "swap URLs" (DNS swap) when done with the environmrnt validation

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