Configuring deployment agents (for example, CodeDeploy agent)

Can you explain the main function of the AWS CodeDeploy agent and why it’s necessary for deployments?

The AWS CodeDeploy agent is a software package that, when installed and configured on an EC2 instance or an on-premises server, facilitates the deployment of applications from AWS CodeDeploy. It is responsible for communicating with the CodeDeploy service to pull deployment artifacts, and then unpacking and deploying those artifacts onto the server. The agent is necessary because it automates the process of deploying the application, ensures that the deployment lifecycle hooks are executed, and provides status updates back to the CodeDeploy service.

How would you install the AWS CodeDeploy agent on an EC2 instance?

To install the AWS CodeDeploy agent on an EC2 instance, you would typically connect to the instance via SSH, and then run the installation commands depending on the operating system. For Amazon Linux, you can use the built-in package manager to install the CodeDeploy agent. For other systems, AWS provides specific commands for downloading and installing the agent. After installation, you should ensure that the CodeDeploy agent service is running and set to automatically start on boot.

What are some of the deployment lifecycle hooks provided by AWS CodeDeploy, and how do you configure them?

AWS CodeDeploy defines a set of deployment lifecycle hooks such as ApplicationStop, BeforeInstall, AfterInstall, ApplicationStart, and ValidateService. These hooks represent points in the deployment process where you can run custom scripts or actions. You configure them by specifying their location and the scripts to run in the appspec.yml file of your application source code. This file maps the lifecycle events to the scripts you want to execute during those events.

How can you check the status of the AWS CodeDeploy agent on a server, and what common issues might indicate that the agent is not functioning properly?

You can check the status of the AWS CodeDeploy agent by running the appropriate command for your server’s operating system; for instance, ‘service codedeploy-agent status’ on Amazon Linux. Common issues that indicate a malfunction include the agent not running, failure to communicate with the CodeDeploy service, or logs indicating errors with deployment processes. Checking the agent logs, which are generally located at /var/log/aws/codedeploy-agent, can provide more insight into specific issues.

Can the AWS CodeDeploy agent be used with on-premises servers, and if yes, what are the prerequisites for setting it up?

Yes, the AWS CodeDeploy agent can be used with on-premises servers. Prerequisites for setting it up include ensuring that the on-premises servers have internet access or access to your AWS resources via a VPC endpoint, the servers are running a supported operating system, and IAM roles and permissions are correctly set up for CodeDeploy to interact with the agent. Additionally, you’ll need to register your on-premises instances with AWS CodeDeploy and configure the agent to reference the correct region and endpoint.

Describe how you would update the AWS CodeDeploy agent on multiple instances at scale?

To update the AWS CodeDeploy agent on multiple instances at scale, you would use a configuration management tool like AWS Systems Manager, Ansible, Chef, or Puppet. These tools can be used to execute commands across multiple instances, allowing you to update the agent without manually connecting to each instance. AWS Systems Manager Run Command is particularly useful because it integrates directly with AWS services and does not require additional agents to be installed.

What are some common configurations you might set for the AWS CodeDeploy agent?

Common configurations for the AWS CodeDeploy agent include setting the log file location, defining log file rotation policies, adjusting the agent’s caching behavior, and configuring proxy settings if the agent is behind a firewall or HTTP proxy. These configurations can be adjusted in the agent’s configuration file, typically located at /etc/codedeploy-agent/conf/codedeployagent.yml.

How does AWS CodeDeploy handle failed deployments, and what role does the agent play in reporting these failures?

AWS CodeDeploy handles failed deployments by stopping the deployment if any lifecycle hook scripts fail and rolling back to the last successful deployment if the rollback configuration is enabled. The CodeDeploy agent plays a crucial role in reporting these failures by executing the lifecycle hooks and updating the deployment’s status based on the success or failure of these hooks. The agent also captures logs that can be sent to Amazon CloudWatch Logs for further analysis.

In what situations would you need to manually intervene with a deployment that is being handled by AWS CodeDeploy?

Manual intervention may be required if there are operational issues that automated processes can’t resolve, such as configuration conflicts on the target instances, problems with application-specific dependencies, or errors within the deployment scripts that require debugging. Additionally, if AWS CodeDeploy is unable to successfully rollback changes after a failed deployment, manual intervention may be necessary to restore service.

Explain how you can use IAM roles with AWS CodeDeploy for secure deployments on both EC2 instances and on-premises servers.

IAM roles are used to provide AWS CodeDeploy with the necessary permissions to interact with other AWS services, such as S3 for artifact retrieval and EC2 for managing instances. When deploying to EC2 instances, you associate an IAM instance profile with the EC2 instances that grants the AWS CodeDeploy agent permission to access the required AWS services. For on-premises servers, you generate an IAM user with the necessary permissions and configure the AWS CodeDeploy agent to authenticate using that user’s access keys.