AWS Bites Podcast Summary: Episode 127 - "Which Load Balancer Should You Use?"
Release Date: July 11, 2024
Hosts: Luciano Mammino and Owen (co-host)
Duration: Approximately 21 minutes
Introduction to Load Balancers
In episode 127 of AWS Bites, hosts Luciano Mammino and Owen delve into the critical role of load balancers in cloud computing architectures. They begin by emphasizing the necessity of load balancers for achieving elastic scalability, high availability, and security. Luciano opens the discussion by posing fundamental questions about load balancers, aiming to clarify their functionality and guide listeners in selecting the appropriate type based on performance, cost, and flexibility.
Notable Quote:
Luciano (00:00): “To get all of that, you'll need a load balancer. But what is a load balancer really? This is the topic of our podcast today.”
Understanding the Need for Load Balancers
The conversation progresses with an illustrative example highlighting the challenges of serving client requests directly from a single server. Luciano outlines the risks of exposing a server to the public internet, such as security vulnerabilities, scalability issues, and single points of failure. He stresses the importance of distributing traffic across multiple instances to ensure application reliability and seamless scaling.
Key Points:
- Security Risks: Direct server exposure can lead to potential security breaches.
- Scalability Constraints: A single server may quickly become overwhelmed under high traffic.
- Single Point of Failure: Downtime can result if the sole server encounters issues.
Features of Load Balancers
Owen elaborates on the essential features that load balancers provide, which are pivotal in managing and distributing network traffic effectively.
Notable Quote:
Owen (03:37): “Feature number one is the ability to distribute the traffic across multiple hosts and solve a lot of those problems you were talking about there.”
Key Features Discussed:
- Traffic Distribution Algorithms: Including round-robin and weighted distribution methods.
- Health Checks: Ensuring traffic is routed only to healthy and responsive servers.
- TLS/SSL Termination: Offloading encryption tasks from application servers to reduce their computational load.
- DDoS Protection and Firewalls: Enhancing security against distributed denial-of-service attacks and other intrusion attempts.
Layer 4 vs. Layer 7 Load Balancers
The hosts transition into a technical exploration of load balancers based on the OSI model, focusing on Layer 4 (Transport Layer) and Layer 7 (Application Layer).
Notable Quote:
Luciano (08:07): “Layer four load balancers operate at the transport layer, they don’t do anything about what we might call the protocol.”
Layer 4 Load Balancers:
- Operation: Handle traffic based purely on transport protocols like TCP or UDP without understanding higher-level protocols.
- Advantages:
- Low Latency: Minimal processing leads to high performance.
- High Throughput: Capable of handling massive amounts of traffic efficiently.
- Disadvantages:
- Limited Feature Set: Cannot perform actions based on application-level data, such as specific HTTP paths.
Layer 7 Load Balancers:
- Operation: Operate at the application layer, understanding protocols like HTTP and HTTPS.
- Advantages:
- Advanced Routing: Can route based on headers, paths, query parameters, and even request bodies.
- Enhanced Features: Supports HTTP compression, detailed health checks, caching, and authentication.
- API Gateway Capabilities: Can function similarly to API gateways with integrated security features.
- Disadvantages:
- Increased Latency: More processing leads to slightly higher latency compared to Layer 4.
Notable Quote:
Owen (10:54): “If you're looking for some more control at the layer 7 layer, then you'll need a layer 7 load balancer because they can see the traffic at that HTTP or HTTPS level.”
AWS Load Balancer Offerings
Luciano provides an overview of AWS's managed load balancer services, highlighting their types and use cases.
Notable Quote:
Luciano (13:09): “In AWS you can of course integrate any kind of third-party load balancer... but there are alternatives that AWS provides in the form of managed services.”
AWS Load Balancer Types:
-
Network Load Balancer (NLB):
- Layer: 4
- Use Cases: Ideal for high-throughput applications requiring low latency.
- Features: Fixed IP addresses, support for TLS termination with AWS Certificate Manager, and capabilities to handle millions of requests per second.
-
Application Load Balancer (ALB):
- Layer: 7
- Use Cases: Suitable for applications needing advanced routing, such as microservices and container-based architectures.
- Features: Path-based routing, support for WebSockets, HTTP/2, GRPC, integration with AWS Lambda, and more sophisticated health checks.
-
Gateway Load Balancer:
- Layer: Specialized use case
- Use Cases: Integrates with third-party security appliances for advanced traffic inspection and filtering.
-
Classic Load Balancer:
- Status: Deprecated
Notable Quote:
Luciano (16:25): “Balancers support everything we talked about in terms of layer 7. You’ve got the path-based routing, etc.”
Pricing Considerations
Luciano addresses the complexities of pricing models for AWS load balancers, emphasizing the pay-as-you-go structure based on time and capacity units.
Key Points:
- Billing Metrics: Charges are based on usage duration (per hour or partial hours) and capacity units (NLB Capacity Units - NLCU for Network Load Balancers and Load Balancer Capacity Units - LCU for Application Load Balancers).
- Additional Costs: Data transfer out beyond 100 GB to the internet incurs extra charges, while intra-VPC data transfer is typically free.
- Capacity Unit Factors for ALBs: Calculated based on new connections, active connections, processed bytes, and rule evaluations.
Notable Quote:
Luciano (20:57): “Pricing can be a little bit difficult when it comes to... you end up with a big spreadsheet if you really want to do a solid model to predict the cost.”
Alternatives to AWS Load Balancers
The discussion concludes by exploring alternatives for those who may prefer not to utilize AWS-managed load balancers.
Options Discussed:
- Third-Party Load Balancers: Tools like NGINX or HAProxy can be hosted on EC2 instances, offering greater customization but requiring more management and expertise.
- DNS Load Balancing: Facilitates geographical traffic distribution but comes with challenges like DNS caching and increased complexity.
- VPC Lattice: A newer AWS offering (further details available in separate episodes and blog posts), which provides additional load balancing and networking capabilities.
Notable Quote:
Luciano (20:57): “But do that only if you really have the skills and you are really knowledgeable about these tools and all the relevant networking configuration.”
Conclusion
Luciano and Owen wrap up the episode by summarizing the key takeaways on choosing the right load balancer within AWS. They encourage listeners to consider their specific application needs, such as the required layer of operation, desired features, performance requirements, and budget constraints when selecting between Network Load Balancers and Application Load Balancers. Additionally, they remind the audience of the available alternatives and the importance of understanding the complexities involved in each option.
Closing Quote:
Luciano (21:00): “Hopefully this was a complete enough coverage of load balancers and how do you use load balancers on AWS? I'm sure that there is a lot we have missed, so let us know if you have any particular experience that might be worth sharing.”
Final Thoughts
Episode 127 of AWS Bites provides a comprehensive guide to understanding load balancers within the AWS ecosystem. Luciano Mammino and Owen effectively break down complex concepts, making the topic accessible to both beginners and seasoned professionals. Whether you're architecting a new application or optimizing an existing infrastructure, this episode offers valuable insights to inform your load balancing strategy.
For more information and to listen to the full episode, visit AWS Bites.