It asks to be able to foresee the installation of varnish and its update from the Plesk panel

I love varnish cache

Magento 2 works great with varnish but it won't work with nginx caching. I read somewhere along the github repo it's because it doesn't provide a way to invalidate cache like varnish.

So in this case nginx caching is not a proper replacement

"Edge sides include ESI can be achieved via Varnish cache sitting between nginx and apache." - YES -pls!

IT WOULD BE GOOD TO HAVE VARNISH CACHE AND / OR MAMECACHED DIRECTLY IN THE APPLICATIONS, WITHOUT PASSING FROM THE DOKER .. IT WOULD BE FANTASTIC ALL THIS. SEMPLIFE VERY WORK

This guide is for the older version of Magento platform. We recommend you to use the latest version of Magento. https://www.cloudways.com/blog/how-to-configure-varnish-cache-magento/

i for one am new to plesk and docker, i would be lost on how to test it up, but to have the option to run it like i can ran nginix within the webspace or like redis from php settings would be great.

Also note Having Varnish hits, it doesn't hit your app at all. Something like redis etc is still slow.
Still having both Varnish, redis can be optional.

Edge sides include ESI can be achieved via Varnish cache sitting between nginx and apache.
Thus nginx will terminate ssl, full cached page if found on Varnish will be served directly. Cache miss will be serviced by apache.
This cannot be achieved via nginx + apache.
This test case is important for many business cases like magento, high traffic full page cached sites etc. Currently only Centos webpanel supports it and cpanel has a third party addon.
Also Varnish has VMODS and some are pretty essential like say, Geoip module.
Plesk dev can test Varnish , and can think to provide is as optional. Varnish is not everyone's cup of tea, still It does have strong business case like magento. It's essential for many clients now, thus having it optional does seems very useful. As for support part, plesk should focus on just the installation and ease to use it and basic funtion. Configuration support is out of scope and community or Internet can provide help.

Varnish cache is a full page cache. Nginx in Plesk is not configured to use caching. Implement Varnish or enable cache in Nginx.

Moving from cPanel to Plesk would be essential if you supported varnish!! :D

We love 12.5 but are replacing with cPanel solely because of not having Varnish.
And those who claim you don't need it etc - what do you know what I need? If I want it, if I think it helps my site, that is my prerogative and my business. There are arguments for both sides, there are believers on one, believers on the other. But there is no denying that many want it and are trying to hack-install it on Plesk 12. A quick google will tell you so. The people HAVE spoken - it IS needed.

I see plesk 12.5 has many options for nginx and php-fpm now in relation to php version.

I would still keep my vote on varnish as i think it would be good for people with really badly configured servers to get better performance easily. ;)

Ps this would be good for me instance. Nginx PHP needs php 5.3. Getting seriously old. Will be updating to newest magento that needs 5.4 Min. I would have the option of placing Varnish infront of apache and using any php verison i needed. Same for many other apps.

As magento 2.0 will feature varnish 4 compatibility, this could be a good option, to run varnish in front of nginx or apache. Or both would be good options.

Benchmarks i have seen have not shown varnish to be that much faster than nginx for magento, but im pretty sure this is a feature many people want and it maybe better in other bench marks.

Myself i would maybe not use varnish, as my servers runs amazingly with nginx. But it would be a great tool to run infront of apache giving access to more php versions for customers that need it etc and giving them a powerful caching front end, giving plesk more versatility and appealing to more customers.

The extension of plesk, must be able the customer to enable/disable the varnish cache for domain, so, if for magento is a nightmare, simply disable it from control panel and will works fine! :)

Varnish is a nightmare especially for carts like Magento, there are already magento extension that do the same thing as varnish without all the hassle for really low prices. This is just a total waste of time.

Can be better if you add also an option for enalbe/disable varnish cache for each domain/subdomain, varnish is an very good cache for website for example wordpress, joomla, drupal many provider offer this type of cache.

Many provider offer cache with varnish but with cpanel, so I think that is better to add also this possibility directly from plesk.

Varnish is a caching proxy that simply serves 'pre-compiled' pages directly from RAM without having to be generated through nginx/apache/php leading to a massive reduction in page load times on the second and subsequent visits.
While integrating it into a control panel will be tricky it should be possible and would be a powerful addition to plesk.