Use HTTP2 server push to improve load times

[nachoparker]

Hi,

This is a paste of my suggestion in this comment as a separate request.

To complement my message on the other post I would like to suggest that some sort of HTTP2 server push is implemented on the server side.

This will allow HTTP2 enabled servers to push assets to the browser even before it fully computes index.php and requests them. Note that assets can be preloaded or prefetched, and we can even preconnect to the server to save TCP connection time.

Also, it should be quite simple to implement. In the case of the NextCloudPi web interface (quite a simple example), it amounts to one line

header("Link: </minified.js>; rel=preload; as=script;,</ncp.js>; rel=preload; as=script;,</ncp.css>; rel=preload; as=style;,</ncp-logo.png>; rel=preload; as=image;, </loading-small.gif>; rel=preload; as=image;, rel=preconnect href=ncp-launcher.php;");

, and the result on a very slow QEMU ARM instance ( gray ball means pushed )

There's some informative links at the bottom of the blog post.

[MorrisJobke]

Regarding the server push: we need to track which assets are already delivered to the specific client to not push all assets that are already cached in the browser.

Regarding the preloading header: yes it may help, but currently we first want to focus on bundling JS files and reduce the number of assets first, because it has a bigger gain in performance first. So we should focus on the low hanging fruits.

See #4045

I hope this is understandable.

[nachoparker]

Regarding the server push: we need to track which assets are already delivered to the specific client to not push all assets that are already cached in the browser.

Please, don't disregard this too easily. The browser/client automatically cancels the push with a RST_STREAM frame when the asset is found in its cache, so cached stuff is not pushed again.

See

https://en.wikipedia.org/wiki/HTTP/2_Server_Push
https://stackoverflow.com/questions/29352282/does-the-browser-cancel-server-push-when-a-resource-is-in-cache
https://www.daveyshafik.com/archives/69603-http2-server-push-youre-doing-it-all-wrong.html

we should focus on the low hanging fruits.

100% aggree, and I know the issue of loading time is being addressed. HTTP2 server push would come after that.

Still I think it would be of value. Any chance to leave it open until its time?

edit: if I understood correctly, the preload header, even if it's not originally made for HTTP2 push, has become the facto the way of signalling it, so for practical purposes they are the same thing

[ad-m]

If HTTP2 Push would be supported, there could be push notification for the (Android) Talk App and Client without Google dependencies (F-Droid version).
Also the Desktop-Client could be sync immediately instead of a pull every 30 sec. Just to name a few :)

You miss following:

HTTP/2 Server Push[1] is not a notification mechanism from server to client. Instead, pushed resources are used by the client when it may have otherwise produced a request to get the resource anyway; this can result in wasted bandwidth if said pushed resources go unused by the client, however.

( https://en.wikipedia.org/wiki/HTTP/2_Server_Push )

Notifications in 2018 year should be made via websocket / EventSource connection . It seems to me that maintaining such in mobile devices can be quite expensive and have an impact on the operation of the device on the battery.

[nachoparker]

Exactly. HTTP2 push is not about push notifications, but about faster load times.

Regarding the server push: we need to track which assets are already delivered to the specific client to not push all assets that are already cached in the browser.

Regarding the preloading header: yes it may help, but currently we first want to focus on bundling JS files and reduce the number of assets first, because it has a bigger gain in performance first. So we should focus on the low hanging fruits.

See #4045

I hope this is understandable.

It seems as it should be possible to set a cookie with an appropriate id for the current generation of css and js. If the browser request contain this id you simply do not push the same resource again.