AWS Network Load Balancer target group suddenly become empty

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We are using EKS version 1.28 with the AWS Load Balancer Controller version v2.6.2 (from Helm chart 1.6.2). Our setup involves an AWS NLB forwarding traffic to a Kubernetes service using TargetGroupBinding, which targets the service. This configuration has been working well, with pods correctly targeted by the target group and traffic flowing smoothly.

However, yesterday, without any action, upgrade, or apparent trigger, the target group suddenly became empty, even though the TargetGroupBinding still existed and had not changed. We investigated the AWS Load Balancer Controller logs and CloudTrail, but found nothing suspicious. A simple rollout of the deployment resolved the issue, and the pods were added back to the target group.

Has anyone encountered this issue before? Do you have any ideas on how to prevent this from happening in the future?

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3 Answers
1

Hello,

please follow the below steps it will be helpful for you.

Investigate Logs and Metrics: Continue investigating AWS Load Balancer Controller logs, CloudTrail logs, and Kubernetes events for any clues regarding the sudden emptying of the target group. Look for any unusual patterns or errors that could indicate a root cause.

Check Pod Health and Stability: Review the health and stability of the pods within your Kubernetes cluster. Look for any evictions, crashes, or other issues that may have caused the pods to be removed from the target group. Ensure that the pods have sufficient resources allocated to them.

Verify AWS EKS and Controller Versions: Ensure that you are using compatible versions of AWS EKS and the AWS Load Balancer Controller. Check for any known issues or bugs related to target group management in the versions you are using. Consider upgrading to newer versions if necessary.

Implement Redundancy and Auto-Scaling: Implement redundancy measures for your Kubernetes cluster and AWS NLB. This could involve deploying multiple instances of the AWS Load Balancer Controller across different availability zones and configuring auto-scaling for your Kubernetes nodes to handle sudden increases in traffic or pod failures.

Enable Monitoring and Alerts: Set up comprehensive monitoring and alerting for your infrastructure. Monitor the health of your pods, target groups, and NLB using AWS CloudWatch metrics and alarms. Set up alerts to notify you of any abnormal behavior or changes in the state of your target groups.

Perform Regular Maintenance: regular maintenance and health checks on your Kubernetes cluster and AWS resources. This includes updating software, reviewing configurations, and checking for any potential issues proactively.

answered 9 days ago
1

AWS NLB target group became empty without any apparent cause. Here are some steps to prevent this from happening again:

1.Check Health Checks: Ensure target group health checks are properly configured and consistently passed by pods.

2.Monitor Pods: Investigate any unexpected pod terminations or restarts using kubectl get events.

3.Network Configuration: Verify there were no changes in VPC configurations, such as route tables, NACLs, or security groups.

4.Enable Monitoring: Use tools like Prometheus, Grafana, and AWS CloudWatch for better visibility and logging.

5.Automate Rollouts: Implement automated health checks and rollouts to quickly recover if the target group becomes empty again.

6.Node Stability: Check for node failures, evictions, or scaling events.

By addressing these areas, you can prevent future issues and ensure stability.

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answered 9 days ago
0
  1. Ensure that the health checks for your target group are correctly configured and that your pods are consistently passing these health checks. If the health checks fail, the pods could be deregistered from the target group.
  2. Check if there were any pod terminations or restarts around the time the issue occurred. Even if you didn’t manually trigger a rollout, something might have caused the pods to restart.
  3. Verify if there were any issues with the nodes in your cluster, such as node failures, evictions, or any scaling events.
  4. Look at the Kubernetes events kubectl get events to see if there were any events that might provide more context, such as errors or warnings related to your service or pods.
  5. Investigate any potential networking issues within your VPC, such as route table changes, NACL changes, or security group modifications that might affect the communication between the load balancer and the pods.
  6. Since a simple rollout of the deployment resolved the issue, consider implementing automated health checks and rollouts as a temporary recovery mechanism if the target group becomes empty again.

To help pinpoint the root cause, it may be useful to implement more comprehensive logging and monitoring around your load balancer, target groups, and Kubernetes pods. Tools like Prometheus, Grafana, and AWS CloudWatch can provide more visibility into the state of your infrastructure and help identify patterns or anomalies leading up to the issue.

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answered 9 days ago

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