AWS DVA-C02 Drill: CodeDeploy Deployment Failures - Diagnosing HEALTH-CONSTRAINTS

Jeff’s Note

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Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.

For AWS DVA-C02 candidates, the confusion often lies in understanding the interplay between CodeDeploy agents, IAM roles, and instance health checks. In production, this is about knowing exactly how the deployment lifecycle depends on both infrastructure setup and proper permissions. Let’s drill down.

The Certification Drill (Simulated Question)

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Scenario

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DataSprint Solutions, a fast-growing SaaS startup specializing in analytics platforms, recently introduced an automated deployment pipeline using AWS CodeDeploy. During a recent deployment to their EC2 fleet running the analytics backend, the deployment suddenly failed with the following error message:

“The overall deployment failed because too many individual instances failed deployment, too few healthy instances are available for deployment, or some instances in your deployment group are experiencing problems. (Error code: HEALTH-CONSTRAINTS)”

The development team needs to quickly identify what might be causing the deployment failure to resume timely releases.

The Requirement:

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Determine the possible causes for the CodeDeploy deployment failure with the HEALTH-CONSTRAINTS error, considering instance health, permissions, and agent status.

The Options

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• A) The CodeDeploy agent was not running on the target EC2 instances receiving the deployment.
• B) The Amazon CloudWatch unified agent was not running on the target instances.
• C) The developer’s IAM role lacks the necessary permissions to perform CodeDeploy deployments.
• D) The instances’ IAM instance profile lacks required permissions that CodeDeploy needs for deploying.
• E) The instances were not configured with proper CodeDeploy health check settings.

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Correct Answer

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A and D

Quick Insight: The Developer’s Imperative

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CodeDeploy requires the agent running on each target instance to orchestrate deployment steps and report success/failure. Without the agent (Option A), deployment won’t progress. Additionally, the EC2 instance must assume an IAM instance profile granting CodeDeploy necessary permissions to access deployment artifacts and lifecycle commands (Option D). Lack of these permissions can cause health check failures or deployment errors.

Options like CloudWatch Agent or developer IAM role are unrelated to deploying to EC2 instances directly, and health check configuration (Option E) is less commonly a direct cause of this error.

Content Locked: The Expert Analysis

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You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?

The Expert’s Analysis

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Correct Answer

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Options A and D

The Winning Logic

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• Option A: CodeDeploy Agent Status
  The CodeDeploy agent is critical software running on EC2 instances, listening for deployment instructions from the service. If it isn’t running or installed, deployments cannot proceed, causing health constraints errors as instances don’t report back successful lifecycle events.

• Option D: Instance Profile Permissions
  For EC2 instances to receive and execute deployment tasks, the IAM instance profile attached must grant permissions such as codedeploy:* actions. Without these permissions, the agent cannot pull artifacts or signal success, which fails health checks leading to deployment failure.

The Trap (Distractor Analysis):

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• Why not B?
  The Amazon CloudWatch unified agent is unrelated to CodeDeploy deployment health. It collects metrics and logs but does not impact deployment operations.

• Why not C?
  The developer’s IAM role typically controls permissions at the management layer but does not restrict the CodeDeploy agent running on instances. The error message points to instance-level issues.

• Why not E?
  While incorrect health check configuration can cause issues, the HEALTH-CONSTRAINTS error largely reflects instance accessibility and agent status problems, not simply misconfigured health checks.

The Technical Blueprint

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# Check CodeDeploy agent status on EC2 instance
sudo service codedeploy-agent status

# Restart CodeDeploy agent if stopped
sudo service codedeploy-agent start

# Verify IAM instance profile attached to EC2
aws ec2 describe-instances --instance-ids i-0123456789abcdef0 --query 'Reservations[].Instances[].IamInstanceProfile'

# Example minimal IAM instance profile policy for CodeDeploy agent:
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "codedeploy:*",
                "s3:Get*",
                "s3:List*"
            ],
            "Resource": "*"
        }
    ]
}

The Comparative Analysis

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Real-World Application (Practitioner Insight)

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Exam Rule

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For the exam, always pick CodeDeploy agent status and instance profile permissions when faced with HEALTH-CONSTRAINTS errors in CodeDeploy.

Real World

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In practice, you might also check network connectivity or deployment group tagging mismatches, but those are less common causes than missing agents or incorrect IAM instance profiles.

(CTA) Stop Guessing, Start Mastering

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Disclaimer

This is a study note based on simulated scenarios for the AWS DVA-C02 exam.