Choosing Between IP and Instance Target Type in AWS Load Balancers for EKS
Hi everyone, I’m Kevin Espiñeira, and this is my first Medium post! As a Platform Engineer working with AWS and Kubernetes, one of the first challanges I encountered in a production EKS environment was effciently exposing services to clients. In this article, I’ll dive into the technical differences between using IP and instance target types in AWS Load Balancer, a critical decision for optimizing our infrastructure.
Understanding AWS Load Balancer Controller and ALB/NLB
The AWS Load Balancer Controller manages the provisioning and lifecycle of AWS load balancers for Kubernetes applications. It leverages annotations on Kubernetes resources to automatically configure and provision Application Load Balancers (ALBs) or Network Load Balancers (NLBs).
AWS Application Load Balancer (ALB): Designed to handle HTTP and HTTPS traffic, ALB operates at the application layer (Layer 7), providing advanced routing, SSL termination, and user authentication.
AWS Network Load Balancer (NLB): Operates at the transport layer (Layer 4) and is optimized for handling volatile traffic patterns, low latency, and high throughput. It routes traffic based on IP protocol data.
Target Type: Instance
When configuring an A/NLB with target-type instance, the traffic is routed to the EC2 instances hosting your pods, utilizing the primary IP of the instance’s network interface (eth0)
alb.ingress.kubernetes.io/target-type: instance
or
service.beta.kubernetes.io/aws-load-balancer-nlb-target-type: instanceHere’s a more detailed breakdown:
Advantages:
- Simplicity: Straightforward setup as it relies on the EC2 instances’ primary IPs.
- Compatibility: Works seamlessly with auto-scaling groups, as new instances are automatically registered.
- Resource Utilization: Consistent use of instance-level metrics for scaling and monitoring.
Disadvantages:
- Latency: Traffic goes through an additional hop via the instance, potentially increasing latency.
- Scalability: Limited by the number of IP addresses on the instances, which can be a bottleneck in high-traffic scenarios.
- Overhead: More overhead in terms of network and resource management, as instances act as intermediaries.
Target Type: IP
With target-type ip, the A/NLB routes traffic directly to the pods, utilizing their individual IP addresses assigned by the AWS VPC CNI. This setup is particularly efficient for dynamic and scalable environments.
alb.ingress.kubernetes.io/target-type: ip
or
service.beta.kubernetes.io/aws-load-balancer-nlb-target-type: ipAdvantages:
- Direct Routing: Traffic is routed directly to the pods, reducing latency and improving response times.
- Flexibility: Better suited for dynamic environments where pods are frequently created and destroyed.
- Efficiency: Eliminates the intermediate step of routing through instances, which can improve overall throughput.
- Granularity: Allows for more precise scaling and traffic management at the pod level.
Disadvantages:
- Complexity: Requires more complex setup and configuration, especially with the AWS VPC CNI.
- Networking Constraints: Needs proper IP address management within the VPC to avoid conflicts and ensure scalability.
- Maintenance: Increased complexity in maintaining network configurations and troubleshooting issues.
Use Cases and Recomendations
For dynamic environments typical in Kubernetes, target-type: ip is often the better choice due to its direct routing and efficiency. However, for simpler, static environments, target-type: instance can be sufficient and easier to manage.
Conclusion
Choosing between IP and instance target types in AWS LB depends on your specific application needs and infrastructure dynamics. By understanding the benefits and limitations of each, you can make informed decisions to optimize your EKS deployments.