In today’s cloud-first world, businesses leverage Amazon Web Services (AWS) for its robust, scalable, and efficient computing resources. Among these, Elastic Load Balancers (ELB) and Application Load Balancers (ALB) are critical for distributing incoming application or website traffic across multiple targets, such as EC2 instances, ensuring high availability and reliability. However, as organizations grow, so do their cloud infrastructure and associated costs. Optimizing these costs without compromising on performance becomes a priority. One effective strategy is consolidating multiple ELBs and ALBs into a single or fewer ALBs. This approach not only simplifies architecture but also significantly reduces costs. This blog post explores the rationale behind consolidation, provides real-world examples, and offers practical guides using Terraform and Kubernetes for implementation.
Why Consolidate AWS Load Balancers?
Cost Benefits: Consolidating multiple ELBs and ALBs into fewer instances can lead to substantial cost savings. AWS charges for each ELB and ALB instance, so reducing the number of instances directly impacts monthly expenses. Moreover, fewer instances translate to lower data processing charges.
Improved Management and Simplicity: Managing a single ALB is inherently simpler than juggling multiple load balancers. This consolidation leads to streamlined operations, easier monitoring, and simplified security policy enforcement, making the IT infrastructure more manageable.
Enhanced Performance and Scalability: A well-configured ALB can efficiently distribute traffic across multiple applications, improving overall application performance. It also allows for easier scaling as demand fluctuates, ensuring that resources are used optimally.
Potential Challenges and Considerations
While consolidating ALBs offers many benefits, there are challenges to consider:
- Loss of Separate AWS WAF Configurations: Combining ALBs means you can no longer apply different AWS WAF rules to each service, instead they would all fall under one rule set. This could be a limitation if services have vastly different security requirements.
- SSL Certificate Management: Managing multiple SSL certificates for different domains on a single ALB requires careful planning to ensure that all certificates are valid and correctly applied.
- Routing Complexity: As the number of services behind a single ALB grows, routing rules can become complex, potentially leading to misconfigurations or inefficiencies.
Real-World Examples of Consolidation
Example 1: E-commerce Platform
Situation: A growing e-commerce platform was using multiple ELBs to manage traffic across its various services, including user authentication, product catalog, and checkout process. Each service had its own ELB, leading to increased costs and complexity in managing multiple load balancers.
Action: The company decided to consolidate its ELBs into a single ALB capable of handling different traffic patterns and routing them to the appropriate services based on the request path. This was achieved by defining path-based routing rules within the ALB.
Outcome: By consolidating into a single ALB, the e-commerce platform saw a 30% reduction in monthly AWS costs. Additionally, the simplified architecture made it easier for the DevOps team to manage the infrastructure, deploy updates, and monitor the system’s health.
Example 2: SaaS Application
Situation: A Software as a Service (SaaS) company operated multiple ALBs to segregate traffic between its internal applications and customer-facing services. This separation was initially intended to enhance security and performance but resulted in higher operational costs and complexity.
Action: The company re-evaluated its infrastructure and decided to merge its ALBs into one, using host-based routing to direct traffic to the appropriate services. Secure communication was ensured by implementing strict security groups and IAM roles.
Outcome: The consolidation led to a 25% decrease in the operational costs associated with managing load balancers. The SaaS provider benefited from a more straightforward architecture, which reduced the time spent on maintenance and allowed for faster deployment cycles.
Terraform Example for ALB Consolidation
To demonstrate how to consolidate multiple services under a single ALB using Terraform, let’s create an ALB setup that routes traffic to two different domains, each with its target group and ACM certificate.
Prerequisites: Assume we have a VPC, subnets, and necessary IAM roles already configured.
Terraform Code Snippet:
resource "aws_lb" "main" {
name = "unified-alb"
internal = false
load_balancer_type = "application"
security_groups = ["sg-123456"]
subnets = ["subnet-123456", "subnet-654321"]
}
resource "aws_lb_listener" "http" {
load_balancer_arn = aws_lb.main.arn
port = 80
protocol = "HTTP"
default_action {
type = "fixed-response"
fixed_response {
content_type = "text/plain"
message_body = "404 Not Found"
status_code = "404"
}
}
}
# Configuration for 2 domains with ACM certificates
variable "domains" {
type = list(object({
domain_name = string
target_group_arn = string
certificate_arn = string
}))
default = [
{
domain_name = "example1.com"
target_group_arn = aws_lb_target_group.example1.arn
certificate_arn = "arn:aws:acm:region:account:certificate/example1"
},
{
domain_name = "example2.com"
target_group_arn = aws_lb_target_group.example2.arn
certificate_arn = "arn:aws:acm:region:account:certificate/example2"
}
]
}
# Listener rules for routing
resource "aws_lb_listener_rule" "host_based_routing" {
for_each = { for idx, domain in var.domains : idx => domain }
listener_arn = aws_lb_listener.http.arn
priority = each.key + 1
action {
type = "forward"
target_group_arn = each.value.target_group_arn
}
condition {
host_header {
values = [each.value.domain_name]
}
}
}
This snippet outlines the creation of an ALB and its configuration to route traffic to two different domains based on host headers. It assumes target groups and ACM certificates are already in place.
Kubernetes Manifest for ALB with ACM & Multiple Services
Moving to Kubernetes, let’s see how we can configure an ALB to manage traffic for two domains with their services using an Ingress object. This example assumes you have an AWS Load Balancer Controller installed in your cluster.
Kubernetes Manifest:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: unified-ingress
annotations:
kubernetes.io/ingress.class: "alb"
alb.ingress.kubernetes.io/scheme: "internet-facing"
alb.ingress.kubernetes.io/target-type: "ip"
alb.ingress.kubernetes.io/listen-ports: '[{"HTTP": 80}, {"HTTPS": 443}]'
alb.ingress.kubernetes.io/actions.ssl-redirect: '{"Type":"redirect","RedirectConfig":{"Protocol":"HTTPS","Port":"443","StatusCode":"HTTP_301"}}'
# Certificates
alb.ingress.kubernetes.io/certificate-arn: "arn1,arn2"
spec:
rules:
- host: example1.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: service1
port:
number: 80
- host: example2.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: service2
port:
number: 80This manifest defines an Ingress resource that directs traffic to two different services based on the requested domain. It uses annotations to specify the ALB settings, including the ACM certificates for HTTPS.
Wrapping Things Up
Consolidating AWS ELBs and ALBs into fewer instances is a strategic move that can lead to significant cost savings, simplified management, and improved scalability. Through real-world examples and detailed guides using Terraform and Kubernetes, we’ve explored how to effectively implement this strategy. However, it’s crucial to consider potential challenges and plan accordingly to ensure a smooth transition and maintain the integrity of your services.
