# CodeDeploy
- A fully managed deploy service in the cloud.
- Can deploy EC2, On-Prem, Lambda, or ECS.
- Rapidly release new features.
- Update AWS Lambda function versions.
- Avoid downtime during application deployments.
- Integrates with existing CI/CD tools eg. Jenkins, [[_CodePipeline|CodePipeline]].
- Integrates with existing management tools eg. Puppet, Chef, Ansible.

## Core Components
### Application
The unique identifier for the application being deployed. Ensures the correct combination of revision deployment configuration, and group are referenced during deployment. 

### Deployment Groups
A set of EC2 instances or [[_Lambda|Lambda Functions]] where the new revision is deployed to.

### Deployment
This is the process and components used to apply a new application revision.

### Deployment Configuration
A set of deployment rules used during deployment - with success/failure conditions included

### AppSpec File
Contains the deployment actions that CodeDeploy should execute during deployment. 

### Revision
This is everything required to deploy a new version: AppSpec file, application files, configuration files, executables.

## Deployments
### In-Place
- The app on each instance in the deployment group is **stopped**.
- The latest app revision is installed, and the new version of the application is started and validated.
- You can use a **load balancer** so that each instance is unregistered during its deployment and then restored to service after the deployment is complete.
- ==Only deployments that use the EC2/On-Premises compute platform can use in-place deployments.==

### Blue/Green
- Instances are provisioned for the replacement environment.
- The latest application version is installed on the replacement instances
- An optional wait time occurs for activities such as application testing and system verification.
- Instances in the replacement environment are registered with an ELB, causing traffic to be rerouted to them.
- Instances in the original environment are unregistered and can be terminated or kept running for other uses.