You are probably aware that Amazon Web Services provides Elastic Load Balancing (ELB) as their preferred load balancing solution on the AWS platform. ELB distributes incoming application traffic across multiple Amazon EC2 instances in the AWS Cloud. Considering the costs involved, and the expertise required to set up your own load balancer solution, ELB can be a very attractive option for rapid deployment of your application stack.
What can often be overlooked involve these few tips and tricks to make sure you are utilizing ELB to best support your application use case and infrastructure. Following is a list of some of the top tips and best practices I’ve found helpful when helping others to set up Elastic Load Balancing.
Load Balancer Best Practices
Read the Docs!
This may seem obvious, but reading the docs and having a good fundamental understanding of how things work will save you a lot of trouble in the long run. There’s nothing like a short hands-on tutorial to get you started while conveying key features. Amazon provides very detailed documentation on how to set up and configure ELB for your environment. A few helpful docs for ELB have been included in the references section of this article. On that note, Amazon also provides recordings of their events and talks on Youtube. These can be very helpful when trying to understand the various AWS services and how they work.
Plan your Load Balancer Installation
Thorough planning is another key practice that can often be overlooked in the rush to implement a new application stack. Take the time to understand your application requirements thoroughly so you know the expected application behavior—especially as it relates to ELB.
Be sure to factor in considerations like budget and costs, use case, scalability, availability, and disaster recovery. This can’t be stressed enough. Proper planning will mean less unforeseen issues down the road, and can also serve to provide your business with a knowledge base when others need to understand how your systems work.
SSL Termination
Along the lines of planning, if you are using SSL for your application (and you should be), plan to terminate it on the ELB. You have the option of terminating your SSL connections on your instances, or on the load balancer.
Terminating on the ELB effectively offloads the SSL processing to Amazon, saving CPU time on your instances which is better used for application processing. It can also save on costs, because you will need less instances to handle application load.
This can also save administrative overhead since ELB termination effectively moves the management to a single point in the infrastructure, rather than requiring management of the SSL certs on multiple servers.
Unless your security requirements dictate otherwise, this can make your life quite a bit simpler.
Configure Cross-Zone Load Balancing
Don’t just place all of your instances into one availability zone inside of an AWS region, and call it a day. When mapping out your infrastructure, plan on placing your instances into multiple AZs to take advantage of cross-zone load balancing.
This can help with application availability and resiliency, and can also make your maintenance cycles easier as you can take an entire availability zone offline at a time to perform your maintenance, then add it back to the load balancer, and repeat with the remaining availability zones.
It’s worth noting that ELB does not currently support cross-region load balancing, so you’ll need to find another way to support multiple regions. One way of doing that is to implement global load balancing.
Global Load Balancing
AWS has a feature in Route 53 called routing policies. With routing policies, you can direct global traffic in a variety of ways, but more specifically direct client traffic to whichever data center is most appropriate for your client and application stack.
This is a fairly advanced topic, with a lot of ins and outs that can’t be covered in this article. See my post, Global Load Balancing Using AWS Route 53, for more details. In short, the best way to learn about this feature in Route 53 is probably to start with the docs, then try implementing it through the use of Route 53 traffic flow.
Pre-warming your ELB
Are you expecting a large spike in traffic for an event? Get in touch with Amazon and have them pre-warm your load balancers. ELBs scale best with a gradual increase in traffic load. They do not respond well to spiky loads, and can break if too much flash traffic is directed their way.
This is covered under the ELB best practices, and can be critical to having your event traffic handled gracefully, or being left wondering what just happened to your application stack when there is a sudden drop in traffic. Key pieces of information to relay to Amazon when contacting them are the total number of expected requests, and the average request response size.
One other key piece of information has to do with operating at scale. If you are terminating your SSL on the ELB, and the HTTPS request response size is small, be sure to stress that point with Amazon support. Small request responses coupled with SSL termination on the ELB may result in overloading the ELBs, even though Amazon will have scaled them to meet your anticipated demand.
Monitoring
One final item, but a very important one. Be sure and monitor your ELBs. This can be done through the AWS dashboard, and can provide a great deal of insight into application behavior, and identifying problems that may arise. You can also use the Sumo Logic App for Elastic Load Balancing for greater visibility into events that, in turn, help you understand the overall health of your EC2 deployment. For example, you can use the Sumo Logic App to analyze raw Elastic Load Balancing data to investigate the availability of applications running behind Elastic Load Balancers.
Conclusion
In this article, we’ve covered best practices for Amazon Elastic Load Balancing, including documentation, planning, SSL termination, regional and global load balancing, ELB pre-warming, and monitoring. Hopefully, these tips and tricks will help you to better plan and manage your AWS ELB deployment.
AWS Elastic Load Balancing: Load Balancer Best Practices is published by the Sumo Logic DevOps Community. If you’d like to learn more or contribute, visit devops.sumologic.com. Also, be sure to check out Sumo Logic Developers for free tools and code that will enable you to monitor and troubleshoot applications from code to production.
References
- Global Load Balancing Using AWS Route 53
- Sumo Logic App for ELB Documentation
- Best Practices in Evaluating Elastic Load Balancing
- AWS Tips, Tricks, and Techniques
- 6 Dos and Don’ts of AWS Elastic Load Balancers
About the Author
Steve Tidwell has been working in the tech industry for over two decades, and has done everything from end-user support to scaling a global data ingestion and analysis platform to handle data analysis for some of the largest streaming events on the Web. He is currently Lead Architect for a well-known tech news site, where he plots to take over the world with cloud- based technologies from his corner of the office.