What is the point of nginx when I have Kubernetes?

Question

As I'm going through Docker/Kubernetes tutorials, I notice a lot of people put nginx into a pod.

Even after reading about nginx, I am not sure what they are using it for. Doesn't Kubernetes serve your app and handle things like load balancing and whatnot?

Isn't something like Node.js a "web server" that can "serve static assets, do caching, and TLS/SSL"?

So with your Node.js app on Kubernetes you have your app being served, static assets, caching especially with things like Redis, and load balancing, etc., why nginx?

Answer 1

Kubernetes is load balancing the requests to your app. Now it is up to you whether you want to expose your app directly or you want to use a WebServer in front of it.

Putting Nginx in front of it would allow you to have things like access logs, error logs, caching, serving static files etc... There are cases where you may want to have your app exposed directly (this is usually the case when you build applications in GoLang)

So Nginx is not a must inside a pod, but it depends on your architecture design whether you want it or not

Answer 2

There can be several reasons why people run an instance of Nginx in a Pod. The most common use case is to serve static assets. For this purpose, Apache or lighttpd will play the same role as well. Without seeing the tutorials, I can't shed light on what role Nginx plays .

Since you mentioned "tutorials", I suspect it's just to serve a static page to say "Hey I'm here! You've successfully deployed something that works.".

To answer your question on k8s handling load-balancing - it does. The Service object does Layer-3 (ie. IP layer) load-balancing between associated pods, and the Ingress object does the same but on Layer-7 (eg. HTTP). Such load-balancing is on a cluster-wide basis.

To summarise, the Nginx in tutorials are likely there just to serve static assets, and k8s load-balances cluster-wide.