[perf] FillNarInfoCache during nix profile's pendingPackagesForInstallation

[savil]

Summary

@Lagoja has a healthy number of devbox global packages. This exposed that devbox add <package> had a perf regression for him:

❯ devbox global add procs

Exec times over 1ms:
"ensurePackagesAreInstalled" took 1.44075ms
"nixEnv" took 2.446083ms
"devbox shellenv --preserve-path-stack -c /Users/johnlago/.local/share/devbox/global/default" took 49.446834ms

Exec times over 1ms:
"devbox shellenv only-path-without-wrappers" took 45.889ms

Installing package: procs@latest.

[1/1] procs@latest
[1/1] procs@latest: Success

Exec times over 1ms:
"syncPackagesToProfile" took 31.80875375s
Recomputing the devbox environment.
"CreateWrappers" took 17.186833ms
"ensurePackagesAreInstalled" took 36.056620833s
"devbox global add procs" took 36.410408875s

See the syncPackagesToProfile taking 31 seconds!

After re-running with --trace, he got the trace.out file at: https://gist.github.com/savil/f6abd6a3adc8e7c92d1d3fd9ecbb93d7

Opening with go tool trace -http=localhost:6060 trace.out shows:

This reveals that we're doing 15 seconds of http requests.

The new codepath does a HEAD request to verify that the binary is still cached in the nix binary cache. The problem is that it does it serially in a for-loop for each package.

Fix
We have a function FillNarInfoCache that spawns goroutines to do it concurrently. This should speed up the time.

How was it tested?

I was able to do devbox global add procs as a sanity check.

[savil]

Current dependencies on/for this PR:

• main
  • PR [perf] FillNarInfoCache during nix profile's pendingPackagesForInstallation #1528 👈

This comment was auto-generated by Graphite.

[mikeland73]

This can't hurt, but is it correct pendingPackagesForInstallation checks all packages when you are only trying to install one of them? That feels weird and it means we're gonna make many more http requests (even if they are in parallel) every time.

[savil]

pendingPackagesForInstallation runs in many different contexts, not just adding packages. Its job is to ensure the nix profile matches the devbox.json, and so it needs to check which of the packages are remaining to be added.

[savil]

I think we can be smarter about when to check for the HEAD request (have some ideas). Will investigate more...

[savil]

I also think merging addPackagesToProfile and tidyProfile would be beneficial