Http on Varnish Cache

HTTP caching basics

Tue, 09 Nov 2021 00:00:00 +0000

It’s important to understand HTTP caching because at some point an HTTP cache will protect your web platform from going down. Whether this HTTP cache is a reverse caching proxy like Varnish or a full-blown CDN, you need to understand the rules of the game, and you need to understand the basics of HTTP caching.

Luckily there are conventions for this. There are even standardized headers that are part of HTTP’s specification that will allow you to control the behavior of a web cache.

Avoiding HTTP to HTTPS redirect loops in Varnish

Tue, 22 Mar 2022 00:00:00 +0000

When your force HTTP to HTTPS redirection in your web server or web application and cache the output, you might get stuck in a redirect loop. Your browser may present the following error message as a result:

Behind the scenes, your browser will receive a 301 Moved Permanently status code and your browser will follow the URL from the Location header:

HTTP/1.1 301 Moved Permanently
Location: https://example.com/
Content-Length: 226
Content-Type: text/html; charset=iso-8859-1
X-Varnish: 2
Age: 0
Via: 1.1 varnish

Despite using an https:// URI scheme, the origin server will continue to issue redirects and you’re in fact stuck in a redirect loop. This loop continues until your browser gives up, at which point the error message will appear.

Object lifetimes: TTL, Grace, Keep

Mon, 01 Jan 0001 00:00:00 +0000

Introduction

If you landed on this page it is very likely that you are familiar with Varnish and you know it improves content delivery performance by storing a copy of your content in cache, and every request thereafter is fulfilled by cached content. Every copy of the content (aka object) stored in cache has a lifetime that defines how long an object can be considered fresh, or live, within the cache.