Server

Running a web server in Kubernetes is easy, but a mail server is more challenging. Most of the challenges have to do with your IP infrastructure, ingress, and load balancer within Kubernetes. Here are things I learned when deploying a mail server based on Postfix on Kubernetes with MetalLB and NGINX ingress. If you have a different setup, things might or might not apply. Prevent mail loops on your secondary MX Your Postfix MX pod is maybe running on a private IP RFC1918, which is fine. But Postfix needs to know its public IP to prevent mail looping if your primary MX is down. You need to define your public incoming IP in the main.cf. So, if you use load balancing, you need to define the public IP for the LoadBalancer that would be the same IP as defined in your DNS MX record, not your outgoing IP. ...

When I was looking at some Nginx caching settings to improve them on a load balanced static content farm. I noticed that the etag headers difference between servers for the same file when they should be the same. So first what is a etag header? From WikipediA The ETag or entity tag is part of HTTP, the protocol for the World Wide Web. It is one of several mechanisms that HTTP provides for web cache validation, which allows a client to make conditional requests. This allows caches to be more efficient, and saves bandwidth, as a web server does not need to send a full response if the content has not changed. ...