Varnish Cache with auto invalidation for ES

[Fifciu]

Hello.
I've just prepared a Varnish configuration with autoinvalidating ES. It is able to really improve your page's speed.

Request to the:

/api/catalog/vue_storefront_catalog_eu/product/_search

Without Varnish (132ms):

With Varnish (79ms):

Elasticsearch is pretty good at caching. However, let's look at extensions that fetch some data from a real backend (M2). Example of my extension that fetches menu without Varnish (791ms):

As you see TTFB is really huge. It is because API sends the request to Magento. So normally it goes through VSF-API -> Magento. When we use Varnish we cache it in front of the VSF-API so the response is... a bit faster! (84ms)

I am also wondering about caching Pull Cart request and invalidate it with Update & Delete. I have to check this idea.

Inside my PR, we have file docker/varnish/README.md there you can find every information I've prepared for developers.
https://github.com/DivanteLtd/vue-storefront-api/blob/342fe2b89ad895578cb2d9fdfdb62cffa20f6231/docker/varnish/README.md

As we have a docker image, we can easily test it locally. We just need to create the same network for each docker-compose. Usually, I run:

docker-compose -f docker-compose.nodejs.yml -f docker-compose.yml up

Then, in another terminal I run:

docker-compose -f docker-compose.varnish.yml up

So when I am experimenting with Varnish's config, I have only to rerun Varnish.
Error or tagless requests should not be cached.

[andrzejewsky]

Really good feature, but it can't be enabled by default. Please try to do something to make varnish as an addon

[Fifciu]

I've rebased it to the new develop. Removed network stuff from docker composes and put configured ones in docker/varnish/docker-compose. Varnish will only work if config.varnish.enabled equals true