Caddy: Http 2 Push wildcard or directory

[dahankzter]

1. What version of Caddy are you using (caddy -version)?

0.10.13

2. What are you trying to do?

I want to avoid having to declare each and every file that should be pushed for a particular route.
Preferably by specifying a directory or some regex specifying matching files.

[tobya]

@dahankzter thanks for the feature request.

Can you provide some use cases where this would be useful? I will make it easier to prioritise this possible feature.

[mholt]

Also with some argument that the performance tradeoff is worthwhile.

[francislavoie]

Just to note @dahankzter you can have your server set a Link header with all the assets needed to push for each route. If you're using some framework for your application, you could write/use a plugin that keeps track of assets you add to pages then when flushing your response you can add the Link header with all the assets included.

I don't disagree that this feature might have some use, but I think generally it can be solved at the application level rather than with Caddy directives, more effectively.

[dahankzter]

This came up when I deployed a Hugo generated site and I just wanted to push some static assets.
I quickly realised I had no idea which resources the generated site wants to serve either javascript or css.

After some firefox network inspection I could find a number of resources but it would have been very neat to just specify "/js" or "/css" and perhaps a logo or so.

It's more of a convenience really because everything I want to do is possible only the config ergonomics are lacking.

[dahankzter]

What I mean is that if I have a custom app where I have full control of what gets served and when I can push myself or use the Link directive. Now I have only a blob of html and resources to serve.

[tobya]

Personally it would seem to me that the strength of _http push_ comes in only pushing assets that are needed, so a general push everything in a directory would not necessarily have my vote to implement.

[dahankzter]

They were all needed on all pages so that prerequisite was met. And like I said it was a generated site where control is very limited.

The idea of having Caddy at all is diminished when having a custom own app. Proxy and static sites are what it's for and providing directories instead of a list of messy files seems very good.

What if the theme I use for Hugo decides to use some other js library or split up the css in different files then I have to fix the Caddy push config as well.

[mholt]

They were all needed on all pages so that prerequisite was met. And like I said it was a generated site where control is very limited.

Except it doesn't account for browser cache...

I'm only mildly excited about server push in the first place, and less so about pushing _all the things_. I think the site owner needs to be very deliberate about what to push in order for it to be effective.

[dahankzter]

Perhaps it's overrated and normal classic edge caching at a cdn is better.

But allowing the config can make sense anyway since it would make a rapidly developing site (that wants to push) less prone to constant config changes which _will be forgotten_ sooner or later.

Is it a difficult change that carries a lot of potential risk and maintenance?

[mholt]

I'm not entirely convinced... sites _in dev_ certainly don't need the performance demands of server push, let alone pushing a whole directory.

Most features like this tend to creep up in complexity more than forethought. So, I appreciate the feature request -- but I think we're not going to do it at this time. Thanks!

[schmkr]

I was also looking for this, for a static web application has resources that have a cache-busting short-hash in their filenames. We cannot use a static configuration like:

push / {
    /assets/fonts/MaterialIcons-Regular.570eb8.woff2
    /assets/chunk.1.ba24f9.css
    /assets/chunk.2.ba24f9.js
}

where those hashes are different every time we deploy a new version.

I solved this by having a script generate a file that has the above configuration and then have the main Caddyfile import it. Heavily inspired by https://github.com/detroitenglish/caddy-push-webpack-plugin but instead of generating the file using a Link header, I generate a file with the push directive.

[mholt]

How a server (as opposed to an actual app) is configured to know which resources to push is -- across all the servers -- a hard problem to solve well.

@schmkr If sky was the limit, how would you like to see this done in Caddy 2?