In our provided WebStack ( nginx -> varnish -> apache ), we have nginx in front, which means all the web traffic from the clients will be terminated at nginx level, since deployed version of nginx has support of HTTP2, client-server communication will be taken place over HTTP2, thus there is no need to worry about the varnish version and its incompatibility of not supporting HTTP2.

Hope this answers your question.

Regards,
Cloudways Team

Dear Cloudways, you suggest having Caching turned on, but you have Varnish 4.0.2 deploying on servers (at least mine). However, Varnish 4.0.2 does not support HTTP/2.

Do you recommend using HTTP/2? Or do you recommend using Varnish?

Do you have plans to upgrade Varnish (or upon request) to 5.0 or higher?

HTTP2 is now fully supported and available for all browsers. It was activated yesterday.

Customers who already have HTTP2 enabled in their servers, need to disable and re-enable it to update browser support. Other customers, just need to enable it (done from Server Settings in NEW CONSOLE).

Cloudways Team

Like Morten Borg I couldn't see this option - so I tried the new Beta Console and there it is.

I can't find it in my Server Settings - is it only available for new servers?

It's great that Cloudways offers HTTP/2!

I've gone ahead and posted a suggestion that folks might want to upvote, a way for Cloudways to resolve the current situation where Chrome users don't benefit from HTTP/2:

"Implement OpenSSL 1.0.2 (or later) for Chrome to benefit from HTTP/2 using ALPN"
http://feedback.cloudways.com/forums/203824-service-improvement/suggestions/7562001-implement-http2

FYI, using webpagetest.org again, when testing from Sydney to my Cloudways web server in New York, it turns out my "Time to First Byte" is much worse with HTTP/2 on. It's bad (grade C) when testing with Firefox, and it's terrible (grade F) when testing with Chrome.

I'm willing to experiment a bit, so I've turned HTTP/2 on. Hopefully my preliminary test results at https://TinkerTry.com/testing-of-http2-underway-at-tinkertry is helpful. Despite this article:
https://www.smashingmagazine.com/2016/02/getting-ready-for-http2/
that states "users with browsers that do not support HTTP/2 will get a slower experience," I am not noticing any such slowdown with Chrome.

Well, tried HTTP/2 again this am, and alas, those initial favorable results were not repeatable, little difference in speed seen before and after HTTP/2, but difference between Chrome and (faster) Firefox was pronounced, see webpagetest.org results, with lables, here:
http://www.webpagetest.org/video/compare.php?tests=160617_K8_NY0,160617_JM_NTC,160617_6B_NRK,160617_H0_NKC

Until I have more time to dive into this, and do retests from various locations, I'm not ready to conclude anything quite yet...

Initial/brief testing of HTTP/2 looking good so far, with webpagetest.org's Chrome/Firefox selection option quite helpful here. Getting about 1.5x slower page loads on Chrome than on Firefox, more testing needed...

Yes, Debian stable (and nearly all other major Linux distros) doesn't support OpenSSL 1.0.2, Updating OpenSSL is a major undertaking as linked to many, many other pieces of software on a system, so it can take a while (if it happens). Checking if we can deploy nginx from the development version of Debian (strech) and keep system mostly stable.

Cloudways Team

Hi.
Yes, I had read that information about Chrome and NPN/ALPN. That was an unfortunate (but forward thinking) move that Google made.

I take it that since Debian does not support OpenSSL 1.0.2, this is the problem? Do you know if Debian is working on an OpenSSL 1.0.2 compliant release?

In any event, you did implement it, and thanks for that.

Yes Bruce, we have released HTTP2 to be activated from Server Settings. Issue is that at the same time, we did it, Google did this:

https://ma.ttias.be/day-google-chrome-disables-http2-nearly-everyone-may-31st-2016/

Essentially it means HTTP2 will NOT be available for Chrome (it will work for other browsers though). Our base servers are Debian and we are checking what is Debian going to do about it although it seems not a trivial situation to get out from.

This is the reason we have not announced it, as after Google decision, it has severely diminished the impact of this feature. We are checking our options and will update here.

You can of course experiment with it as long as you use any other browser but Chrome.

Cloudways Team

It looks like there is a setting in Server > Settings and Packages > Advanced that allows you to turn on HTTP/2 now.
So this has been implemented (but not announced)?

According to https://kinsta.com/learn/what-is-http2/ supporting http/2 is inevitable. Pls do it sooner then later!

HTTP2 will be the new standard very soon. There is also backwards compatibility for older browsers, in that they can still connect via HTTP.
Let's make this happen guys :)

As said, we are analyzing implementation options. It is not straightforward and ,although it brings improvements. there are caveats (i.e. implementations on browsers only support HTTPS).

We are not going to implement it for the sake of just saying we have it, but in a way that brings real benefits and it is perfectly integrated with the applications we support.

Cloudways Team

this looks to be a significant development in terms of speed, so please do it...

Is it hard to implement it?

Signed up for free trial to test cloudways, then realized no HTTP/2. Just canceled trial. Without HTTP/2 there is not point to even trying CloudWays.