Advanced CodeDeploy; The AppSpec File

AppSpec File - Lambda Deployments

The AppSpec File is used to define the parameters that will be used for a CodeDeploy Deployment. The file structure depends on whether you are deploying to Lambda or EC2 / On Premises.

For Lambda Deployments, the AppSpec File may be written in YAML or JSON and contains the following fields:

  • Version
    • reserved for future use - currently the only allowed value is 0.0
  • Resources
    • The name and properties of the Lambda function to deploy
  • Hooks
    • Specifies Lambda functions to run at set points in the deployment lifecycle to validate the deployment
      • e.g. validation tests to run before allowing traffic to be sent to your newly deployed instances

appspec.yml File - Lambda Example

 version: 0.0
 resources:
    - myLAmbdaFunction:
        Type: AWS::Lambda::Function
        Properties:
            Name: "myLambdaFunction"
            Alias: "MyLambdaFunctionAlias"
            CurrentVersion: "1"
            TargetVersion: "2"
hooks:
    - BeforeAllowTraffic: "LambdaFunctionToValidateBeforeTrafficShift"
    - AfterAllowTraffic: "LambdaFunctionToValidateAfterTrafficShift
  • Properties fields are mandatory for Lambda

AppSpec File - Hooks - Lambda

The following hooks are available for use:

  • BeforeAllowTraffic
    • Used to specify the tasks or functions you want to run before traffic is routed to the newly deployed Lambda function
      • e.g. test to validate that the function has been deployed correctly
  • AfterAllowTraffic
    • Used to specify the tasks or functions you want to run after the traffic has been routed to the newly deployed Lambda function
      • e.g. test to validate that the function is accepting traffic correctly and behaving as expected

AppSpecFile - EC2 and On Premises

  • version
    • Reserved for future use - currently the only allowed value is 0.0
  • OS
    • The Operating System version you are using, e.g. linux, windows
  • files
    • The location of any appliccation files that need to be copied and where they should be copied to (source and destination folders)
  • Hooks
    • Lifecycle event hooks allow you to specify scripts that need to run at set points in the deployment lifecycle
      • e.g. to unzip application files prior to deployment, run functional tests on the newly deployed application, and to de-register and re-register instances with a load balancer

For EC2 and On Premises deployments, the appspec.yml file must be placed in the root directory of your revision - this is the directory containing your application source code, otherwise the deployment will fail

Typical setup looks like this:

  • mywebapp folder:
    • appspec.yml
    • /Scripts - scripts you want to run (3 directories)
    • /Config - config files
    • /Source - source files

appspec.yml File - EC2

version: 0.0
os: linux
files:
    - source: Config/config.txt
      destination: /webapps/Config
    - source: Source
      destination: /webapps/myApp
hooks:
    BeforeInstall:
        - location: Scripts/UnzipResourceBundle.sh
        - location: Scripts/UnzipDataBundle.sh
    AfterInstall:
        - location: Scripts/RunResourceTests.sh
          timeout: 180
    ApplicationStart:
        - location: Scripts/RunFunctionalTests.sh
          timeout: 3600
    ValidateService:
        - location: Scripts/MonitorService.sh
          timeout: 3600
          runas: codedeployuser
  • runas: codedeployuser - IAM user set up with permissions for codedeploy

AppSpec File - Supported Hooks for EC2 and On Premises

Set of EC2 instances sitting behind a load balancer. Update using CodeDeploy:

  • BeforeBlockTraffic
    • run tasks on instances before they are deregistered from a load balancer
  • BlockTraffic
    • Deregister instances from a load balancer
  • AfterBlockTraffic
    • Run tasks on instances after they are deregistered from a load balancer

- Steps you would normally need to do when upgrading any application

  • ApplicationStop
    • Gracefully stop the application in preparation for deploying the new version
  • DownloadBundle
    • The CodeDeploy agent copies the application revision files to a temporary location
  • BeforeInstall
    • Details of any pre-installation scripts
      • e.g. backing up the current version, decrypting files
  • Install
    • The CodeDeploy agent copies the application revision files from their temporary location to their correct location
  • AfterInstall
    • Details of any post-installation scripts
      • e.g. configuration tasks, change file permissions
  • ApplicationStart
    • Restarts any services that were stopped during ApplicationStop
  • ValidateService
    • Details of any tests to validate the service

- Hooks related to re-registerring instances

  • BeforeAllowTraffic
    • Run tasks on instances before they are registered with a load balancer
  • AllowTraffic
    • Register instances with a load balancer
  • AfterAllowTraffic
    • Run tasks on instances after they are registered with a load balancer

3 stage process:

  1. deregister systems from load balancer
  2. tasks you need to do to upgrade application
  3. tasks to re-register with load balancer

These events are referred to as the run order of hooks

CodeDeploy Advanced Settings - Exam Tips

  • The AppSpec file defines all the paramters needed for the deployment
    • e.g. location of application files and pre/post deployment validation tests to run
  • For EC2 / On Premises systems, the appspec.yml file must be placed in the rot directory of your revision (the same folder that contains your application code) Written in YAML
  • Lambda supports YAML or JSON
  • Run order for hooks in a CodeDeploy Deployment (see above)