Varnish is a reverse proxy web accelerator  Written in C designed to improve HTTP performance by using server side caching.
In this video I’m going to go through how Varnish works, we will spin up a Varnish docker container and finally talk about the pros and cons of this tech.
Agenda

Classic HTTP Architecture
How Varnish Works?
HTTP Setup - Varnish
HTTPS Setup - Varnish with Caddy as TLS Terminator.
Varnish Pros & Cons
Summary

Pros

Cache & prefetching documents
Resolve DNS hostnames in documents
Rewrite scripts to optimize code
Load Balancing
Backend Connection Pooling
Varnish Modules (VMODS, e.g. rewrite headers)
Edge side includes (personalized dynamic page)

Cons

Cache Invalidation
Only works on unencrypted HTTP
For HTTPS frontend, terminate TLS
For HTTPS backend, no solution in Varnish open source
Can’t cache POST requests (e.g. GraphQL queries)
HTTP/2 backends won’t benefit

docker commands
docker run --name varnish -p 8080:80 varnish
docker cp default.vcl varnish:/etc/varnish
default.vcl
vcl 4.0;
backend default {
.host = "husseinmac";
.port = "2015";
}
timecodes
Classic HTTP Architecture : 1:53
How Varnish Works 3:50
Demo HTTP 7:50
Demo HTTPS 18:23
Varnish Pros 28:43
Varnish Cons 39:26
Cards:
Connection Pooling 2:15 https://www.youtube.com/watch?v=GTeCtIoV2Tw
Layer 4 vs Layer 7 Load balancing 6:25 https://www.youtube.com/watch?v=aKMLgFVxZYk
GET vs POST 6:48 https://www.youtube.com/watch?v=K8HJ6DN23zI
Postgres NodeJS Chrome 8:23 https://www.youtube.com/watch?v=0JNq46eFuOM
Redis 46:13 https://www.youtube.com/watch?v=sVCZo5B8ghE
TLS Termination 49:35 https://www.youtube.com/watch?v=H0bkLsUe3no
tags:
varnish http accelerator, varnish pros and cons, varnish with https, varnish disadvantages
Resources
edge side includes
https://www.fastly.com/blog/using-esi-part-1-simple-edge-side-include
Cache invalidation varnish
https://www.smashingmagazine.com/2014/04/cache-invalidation-strategies-with-varnish-cache/
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