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nginxload-balancing
Nikita
Nikita

Reputation: 857

Clarification of nginx and load balancing needed

I'm now reading design of Instagram and I found such a description of their load balancing system.

Every request to Instagram servers goes through load balancing machines; we used to run 2 nginx machines and DNS Round-Robin between them. The downside of this approach is the time it takes for DNS to update in case one of the machines needs to get decomissioned. Recently, we moved to using Amazon’s Elastic Load Balancer, with 3 NGINX instances behind it that can be swapped in and out (and are automatically taken out of rotation if they fail a health check). We also terminate our SSL at the ELB level, which lessens the CPU load on nginx. We use Amazon’s Route53 for DNS, which they’ve recently added a pretty good GUI tool for in the AWS console.

The question is. Am I right that for now they have a DNS Server which uses RR to decide on which nginx server to send the request. And each of this nginx servers at their turn resends the request to a cluster?

And the second question is. What the difference between nginx and load balancer. Why cannot we use nginx instead?

Upvotes: 4

Views: 546

Answers (1)

Neal Magee
Neal Magee

Reputation: 1701

For your first question, I believe the answer seems to be that Instagram now uses Route53 to map DNS to an Elastic Load Balancer, which does two things: It routes traffic fairly evenly to three NGINX load balancers, and it provides SSL for all traffic. The NGINX servers then act as load balancers to content/application servers further down the stack. Using an ELB instead of round-robin DNS means they can add/remove/update instances attached to the ELB without ever having to worry about DNS updates or TTL.

As for the second question, you can use NGINX just as easily as HAproxy or other services to do load balancing. I am sure that part of the appeal to Instagram in choosing NGINX is its incredible speed and that it's asynchronous and "event-driven" instead of threaded like Apache2. When set up properly, that can mean less headaches under heavy loads.

Upvotes: 4

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