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AWS CodeDeploy

CodeDeploy is a fully managed deployment service that automates software deployments to a variety of compute services, such as EC2, Lambda and on-premise servers.

Useful Links

General Notes

  • Deployment approaches:
    • In-Place
      • Application is stopped on each instance and the new release is installed
      • Known as rolling update
      • Reduces capacity during deployment
        • Stop instance (remove from ELB)
        • Install new revision on stopped instance
        • Start instance (adds back to ELB)
        • Continues to deploy to next instance
      • For rollback you need to re-deploy the previous version
      • Not supported for Lambda
      • Great for deploying for the first time and for dev/test environments
    • Blue/Green
      • New instances are provisioned and the new release is installed on the new instances
      • Blue represents the active deployment, green is the new release
      • Seamless approach, doesn't impact capacity
        • Create new instances (green)
        • Install new revision on new instances
        • Adds new instances to ELB
        • Traffic is routed away from the old instances (blue)
        • Old instances are removed from ELB and terminated
      • For rollback just make ELB route traffic back to the original (blue) environment
        • Only possible if you haven't already terminated the old instances
      • You pay for 2 environments until you terminated the old instances
      • Safest option for production envrionment
  • AppSpec file is a configuration file that defines the parameters to be used during deployment
    • For EC2 and on-prem systems, only YAML is supported
    • For Lambda and ECS, both YAML and JSON are supported
    • It is used to manage each deployment as a series of lifecycle event hooks, which are defined on the event hooks
    • The event hooks and file structure depends on the target (EC2, Lambda or ECS)
    • The appspec.yml file must be placed in the root of the directory of your revision
  • The content in the resources section of the AppSpec file varies, depending on the compute platform of your deployment
resources:
    # Lambda
    - lambda-function:
        type: "AWS::Lambda::Function"
        properties:
            # all required
            name: name-of-lambda-function-to-deploy
            alias: alias-of-lambda-function-to-deploy
            currentversion: version-of-the-lambda-function-traffic-currently-points-to
            targetversion: version-of-the-lambda-function-to-shift-traffic-to
    # ECS
    - ecs-service:
        Type: "AWS::ECS::Service"
        Properties:
            # required
            TaskDefinition: task-definition-ARN
            LoadBalancerInfo:
                ContainerName: ECS-container-name-for-your-ECS-app
                ContinerPort: port-used-by-your-ECS-application
            # optional
            PlatformVersion: ECS-service-platform-version
            NetworkConfiguration:
                AwspcConfiguration:
                    Subnets: ["ecs-subnet-1", "ecs-subnet-n"]
                    SecurityGroups: ["ecs-security-group-1", "ecs-security-group-n"]
                    AssignPublicIp: "ENABLED-or-DISABLED"
  • You can use CodeDeploy agent on an EC2 instance or on-prem server
    • It is required only if you deploy to an EC2 instance on on-prem server, it isn't required for ECS and Lambda deployments
  • CodeDeploy agent archives revisions and log files on instances and cleans up these artifacts to conserve disk space
    • Application revision deployment logs:
      • You can use :max_revisions option in the agent configuration file to specify the number of revisions to archive
      • The agent will also archive the log files for those revisions
      • All others are deleted, with the exception of the log file of the last successful deployment, which is always retained, even if the number of failed deployments exceeds the number of retained revisions
      • If no value is specified, it retains the five most recent revisions in addition to the currently deployed revision
    • CodeDeploy logs:
      • Log file is rotated daily at midnight (instance time)
      • Logs are deleted after seven days
  • You can configure CodeDeploy agent to capture wire log from S3 by setting :log_aws_wire: to true and specify a custom location to store the logs with :log_dir:
  • When there is a deployment phase with content overwrite option as "Overwrite", it will delete all files from previous deployment session
    • If this deployment fails, to restore previous working deployment, either Manual or Automatic rollback must be enabled
    • Files that are deleted as part of the deployment phase need to be added manually
  • If you accidentally deleted the deployment log file on an instance, CodeDeploy does not create a replacement log file
    • To create a new log file, you need to restart CodeDeployAgent

Lifecycle Event Hooks

  • Lifecycle event hooks are run in a specific order known as run order
  • You don't need to use all hooks, just pick the ones that make sense for your application deployment process
  • For the exam is good to have a high level understanding of the logical flow and the run order
  • Some events cannot be scripted, you can just specify files to reference
  • EC2
    • In-place deployment works in 3 broadly phases
    • Phase 1: de-register instances from ELB
      • BeforeBlockTraffic: tasks you want to run on instances before they are de-registered from ELB
      • BlockTraffic: de-register instances from ELB. Cannot be scripted.
      • AfterBlockTraffic: tasks you want to run on instances after they are de-registered
    • Phase 2: actual deployment
      • ApplicationStop: tasks you need to run to gracefully stop your application
      • DownloadBundle: CodeDeploy agent copies the application revision files to a temporary location. Cannot be scripted.
      • BeforeInstall: pre-install scripts, e.g. decrypting files, backing up current version
      • Install: copy application revision files to final location. Cannot be scripted.
      • AfterInstall: post-install scripts, e.g. configuration, file permissions, etc
      • ApplicationStart: start any services that were stopped during ApplicationStop
      • ValidateService: run tests to validate the service
    • Phase 3: re-register instances in ELB
      • BeforeAllowTraffic: tasks you want to run on instances before they are re-registered in ELB
      • AllowTraffic: re-register instances in ELB. Cannot be scripted.
      • AfterAllowTraffic: tasks you want to run on instances after they are re-registered to ELB
  • ECS
    • The event hooks actions are Lambda functions
    • BeforeInstall
    • Install: Cannot be scripted.
    • AfterInstall
    • AllowTestTraffic: Cannot be scripted.
    • AfterAllowTestTraffic
    • BeforeAllowTraffic
    • AllowTraffic: Cannot be scripted.
    • AfterAllowTraffic
  • Lambda
    • The event hooks actions are Lambda functions
    • BeforeAllowTraffic
    • AllowTraffic: Cannot be scripted.
    • AfterAllowTraffic
    • The function needs to use CodeDeploy SDK to get the deployment id and event hook id and return a validation test result, with either 'Succeeded' or 'Failed'
    • The deployment fails if CodeDeploy is not notified by the Lambda function within one hour