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NixOS / hydra

Hydra, the Nix-based continuous build system
http://nixos.org/hydra
GNU General Public License v3.0
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Eval errors make jobset and eval pages very expensive to serve and browse #1362

Open mweinelt opened 4 months ago

mweinelt commented 4 months ago

Describe the bug Eval errors make up a large part of what hydra has to ship to users when browsing jobsets or evals.

To Reproduce Steps to reproduce the behavior:

  1. Go to https://hydra.nixos.org/jobset/nixpkgs/staging-next or https://hydra.nixos.org/eval/1804223
  2. Observe the download size
  3. Strip the HTML around the eval errors
  4. Notice it takes up >99.9% of size

Expected behavior These pages should be quick to load and not create load on the hydra webserver.

Proposal Create a separate route for requesting eval errors and embed that endpoint via an iframe that gets lazily loaded, when it comes into the viewport.

The eval errors should also be shipped in plaintext and not be passed through the template engine.

Hydra Server: hydra.nixos.org

Hydra 0.1.20240126.838648c (using nix-2.19.4).

delroth commented 4 months ago

FWIW when I checked the SQL query associated with loading that page returned 225MB of data. I'm not sure how it ends up getting condensed to 25MB though, but if I did actually get the 225MB measurement right then it's an even more critical performance issue.

Create a separate route for requesting eval errors and embed that endpoint via an iframe that gets lazily loaded, when it comes into the viewport.

Or just make it a link? I don't think we lose much by not having the errors be inline in the page, tbf. If that simplifies the implementation...

mweinelt commented 4 months ago

Given that browsers do the heavy lifting for us, I think iframes can be the drop-in replacement.

https://web.dev/articles/iframe-lazy-loading

samueldr commented 4 months ago

Why even go for an iframe?

Using a discrete page is always the better choice. That is, rather than trying to be "smart" with lazy loading, and/or js, and/or DOM-based tabs.

Though since the expectations vary wildly with tab-based navigation, it would be best if it was a discrete link/action in the blurb above the search input.

mweinelt commented 4 months ago

Why even go for an iframe?

No strong opinion. My impression was that it would be the simplest drop-in replacement.

delroth commented 2 months ago

I've done another pass in https://github.com/NixOS/hydra/commit/6189ba9c5e5308e17a7d1fb7f38443272a70f072 this time actually removing DB fetches when possible. h.n.o loads considerably faster. There are probably some other places where errormsg is being fetched right now, so I'll leave this open for a bit, but I think we might end up just closing the issue if the remaining places don't cause issues.