CodeDeploy

• Deploy our application automatically to multiple EC2 instances
• These instances are not managed by Elastic Beanstalk
• There are several ways to handle deployments using open source tools (Ansible, Terraform, Chef, Puppet, etc…)
• CodeDeploy is the alternative to these tools

CodeDeploy - How it works

• Each EC2 Machine (or On Premise machine) must be running the CodeDeploy Agent
• The agent is continuously polling AWS CodeDeploy for work to do
• CodeDeploy sends appspec.yml file.
• Application is pulled from GitHub or S3
• EC2 will run the deployment instructions
• CodeDeploy Agent will report of success / failure of deployment on the instance

Additional information

• EC2 instances are grouped by deployment group (dev / test / prod)
• Lots of flexibility to define any kind of deployments
• CodeDeploy can be chained into CodePipeline and use artifacts from there
• CodeDeploy can re-use existing setup tools, works with any application, auto scaling integration
• Note: Blue / Green only works with EC2 instances (not on premise)
• Support for AWS Lambda deployments (we’ll see this later)
• CodeDeploy does not provision resources

AWS CodeDeploy - Primary Components

• Application: unique name
• Compute platform: EC2/On-Premise or Lambda
• Deployment configuration: Deployment rules for success / failures
  • EC2/On-Premise: we can specify the minimum number of healthy instances for the deployment.
  • AWS Lambda: specify how traffic is routed to our updated Lambda function versions.
• Deployment group: group of tagged instances (allows to deploy gradually)
• Deployment type: In-place deployment or Blue/green deployment:
• IAM instance profile: need to give EC2 the permissions to pull from S3 / GitHub
• Application Revision: application code + appspec.yml file
• Service role: Role for CodeDeploy to perform what it needs
• Target revision: Target deployment application version

CodeDeploy AppSpec

• File section: how to source and copy from S3 / GitHub to filesystem
• Hooks: set of instructions to do to deploy the new version (hooks can have timeouts).The order is:
  • ApplicationStop
  • DownloadBundle
  • BeforeInstall
  • Install
  • AfterInstall
  • ApplicationStart
  • ValidateService: really important
  • BeforeAllowTraffic
  • AllowTraffic
  • AfterAllowTraffic

Deployment Config

• Configs:
  • One a time: one instance at a time, one instance fails => deployment stops
  • Half at a time: 50%
  • All at once: quick but no healthy host, downtime. Good for dev
  • Custom: min healthy host = 75%
• Failures:
  • Instances stay in “failed state”
  • New deployments will first be deployed to “failed state” instances
  • To rollback: redeploy old deployment or enable automated rollback for failures
• Deployment Targets:
  • Set of EC2 instances with tags
  • Directly to an ASG
  • Mix of ASG / Tags so we can build deployment segments
  • Customization in scripts with DEPLOYMENT_GROUP_NAME environment variables

Deployment types

• In place deployment
  • half the time
• Blue / Green Deployment
  • Attached to one auto scaling group of instances
  • new auto scaling group of instances created (green)
  • if it passes the health checks, version 1 (original asg) is deleted (blue)

CodeDeploy to EC2

• We define how to deploy the application using appspec.yml + deployment strategy
• CodeDeploy will do in-place updates to EC2 our fleet of instances
• We can use hooks to verify the deployment after each deployment phase

CodeDeploy to ASG

• In place updates:
  • CodeDeploy updates the current EC2 instances
  • Instances newly created by ASG will also get automated deployments
• Blue / green deployment:
  • A new auto-scaling group is created (settings are copied from the existing one)
  • We can choose for how long we keep the old instances
  • Blue/Green deployment in order to work we must be using an ELB

CodeDeploy Rollbacks

• In some situation we have to roll back our deployment to a previous working version
• We can specify automated rollback options
  • We may want to rollback when deployment fails
  • We may want to rollback when a CloudWatch alarm threshold is met
  • We can disable rollbacks entirely
• If a rollback happens, CodeDeploy will redeploy the last known good revision as a new deployment => new version number