git Last Modified Performance Issues

[craigerskine]

Operating system

macOS Tahoe 26.1

Eleventy

3.1.2

Describe the bug

I just updated to node v25.1.0 and one of my sites is taking over 15s to build. It normally builds in about 0.18s. I tracked it down to this:

11tydata.json:

{
  "date": "git Last Modified"
}

If I downgrade node to v20.X the site builds in 3s.

Reproduction Source Code URL

https://github.com/craigerskine/cmx.media

Screenshots

No response

[zachleat]

That feature is slow. How many templates does it apply to?

That said, I do see some difference locally on eleventy-base-blog (scoped to 5 template files using a directory data file) between Node 20 and some slowness introduced in Node 22:

Node 20.19.3:
Copied 2 Wrote 16 files in 0.18 seconds (v3.1.2)

Node 22.21.1:
Copied 2 Wrote 16 files in 0.48 seconds (v3.1.2)

Node 24.11.1:
Copied 2 Wrote 16 files in 0.47 seconds (v3.1.2)

Node 25.2.0:
Copied 2 Wrote 16 files in 0.47 seconds (v3.1.2)

[zachleat]

Related #3959 #3912

[zachleat]

This uses import { spawn } from "node:child_process"; under the hood, if there is some Node variability between versions there!

Link to our code:

eleventy/src/Util/Git.js

Line 1 in a9ee377

import { spawnAsync } from "./spawn.js";

[craigerskine]

That feature is slow. How many templates does it apply to?

That said, I do see some difference locally on eleventy-base-blog (scoped to 5 template files using a directory data file) between Node 20 and some slowness introduced in Node 22:

Node 20.19.3:
Copied 2 Wrote 16 files in 0.18 seconds (v3.1.2)

Node 22.21.1:
Copied 2 Wrote 16 files in 0.48 seconds (v3.1.2)

Node 24.11.1:
Copied 2 Wrote 16 files in 0.47 seconds (v3.1.2)

Node 25.2.0:
Copied 2 Wrote 16 files in 0.47 seconds (v3.1.2)

341 Templates.

I want to automate a list of the 6 newest entries without me having to manually add a date frontmatter. I tried all the other date options but when the site is deployed at Netlify git Last Modified is the only thing that really works.

[pachewise]

Yeah, unfortunately it may be very likely spawn: for example, see https://blog.val.town/blog/node-spawn-performance/

I spent some time looking, and the git log approach is the cleanest way to do this until git last-modified is available, so users may have to suffer through this performance overhead until Node devs improve the spawn performance again. The only other optimization I can suggest would be trying to batch these git calls into one "script", so you only have to spawn a single process, but that may be just as slow or slower than the current approach (and is more complicated), given the potential piping or buffering costs... (that said, I haven't tested this yet)

[zachleat]

I’d consider home base for this one to be e18e/ecosystem-issues#216 from facebook/docusaurus#11208

We do have some warnings on the docs around this here: https://www.11ty.dev/docs/dates/

Going to move this one to a discussion until there is a clear path forward.

[zachleat]

Hmm, seeing that it works much faster in Node 20 makes me think I moved this one prematurely.

I would note the docs at https://www.11ty.dev/docs/javascript-runtime/#odd-numbered-versions-of-node-js on odd versions of Node.

@craigerskine: Does it work faster on Node 24?

[craigerskine]

Node v24.12 takes 21 seconds to build, so no. :(