Scenario 9: CloudWatch Agent Failing to Report Metrics

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Problem:

• An EC2 instance stops sending system metrics like CPU, memory, and disk I/O to CloudWatch.
  
  

• Performance monitoring is disrupted, making it hard to troubleshoot proactively.
  
  

Step-by-Step Troubleshooting:

1. Check Agent Status and Logs:
   
   

   • Log into the EC2 instance via SSH.
     
     

   • Check the status of the CloudWatch Agent using commands like sudo systemctl status amazon-cloudwatch-agent.
     
     

   • Review the agent logs located at /opt/aws/amazon-cloudwatch-agent/logs/ for any errors or warnings.
     
     

   • Identify issues such as misconfigured files, permission errors, or network problems in the logs.
     
     

2. Validate the Configuration File:
   
   

   • Locate the CloudWatch Agent configuration file, usually in JSON format.
     
     

   • Verify that the file includes all necessary metrics like CPU, memory, and disk I/O.
     
     

   • Use the command amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -c file:<path-to-config> to reload the configuration.
     
     

   • Ensure there are no syntax errors in the configuration file.
     
     

3. Verify IAM Permissions:
   
   

   • Check the IAM role attached to the EC2 instance.
     
     

   • Ensure it has the required permissions, such as cloudwatch:PutMetricData.
     
     

   • If needed, attach the Amazon managed policy CloudWatchAgentServerPolicy to the IAM role.
     
     

   • Confirm that temporary credentials are valid and not expired.
     
     

4. Update and Restart the Agent:
   
   

   • Check if the CloudWatch Agent is running the latest version.
     
     

   • Update the agent if an older version is in use.
     
     

   • Restart the agent using sudo systemctl restart amazon-cloudwatch-agent.
     
     

   • Monitor if metrics start appearing in CloudWatch after the restart.
     
     

5. Test Connectivity:
   
   

   • Use curl to test connectivity to the CloudWatch endpoints.
     
     

   • Confirm that the instance can reach URLs like https://monitoring.<region>.amazonaws.com.
     
     

   • Rule out VPC-level network issues, such as blocked outbound traffic or DNS resolution failures.
     
     

   • Ensure the instance has proper internet access or VPC endpoints if in a private subnet.
     
     

Key AWS Terms:

• CloudWatch Agent: A tool that collects and sends metrics and logs to CloudWatch.
  
  

• IAM Role: A set of permissions assigned to an EC2 instance to allow it to interact with AWS services.
  
  

• CloudWatch: AWS service for monitoring and observability.
  
  

• Configuration File: A JSON file defining which metrics the CloudWatch Agent should collect.
  
  

• VPC Endpoints: Private connections to AWS services from within a VPC.
  
  

Interview Insight:

• When CloudWatch metrics stop reporting, I start by checking the agent logs and configuration for issues.
  
  

• I verify that IAM roles are correctly set up with permissions to publish metrics.
  
  

• I also check for network issues that might prevent communication with CloudWatch and ensure the agent is up to date and running properly.