"Cross build" next.js app for a different architecture

[escherstair]

Goals

1. Being able to use a development machine with an hardware architecture to "cross build" a next.js app for a deployment machine with another architecure (i.e. developing on amd64 and deployng to arm64). Same OS on both the machines

Non-Goals

1. Being able to "cross build" for different OS between development and deployment

Background

I need to develop my next.js app so that it can run both on amd64 and arm64 architectures running Linux.
I develop on amd64 then I need to setup my CI/CD.
I have two solutoons:

• either using two different CI/CD flows running on two different architectures - this requires doubling the resources
• or using docker + buildx + qemu (or similar one) to emulate - this has performance really slow (unacceptable)

I see that I can use --cpu flag of npm to download and install packages for a different architecture.
And this solves the "install" phase.
To be honest, npm has also --os flag, but I'm not interested in it.

I would like having an optional similar flag --cpu for next build.

Proposal

I would like having --cpu flag for next build
next build --cpu arm64
next build --cpu amd64

I can't help developing but I can help testing it.

[escherstair]

sorry for pushig, but is there any way to get this behavior with next.js?
If not, could this be an idea for future development?

[icyJoseph]

What problem have you experienced, or I should ask, which bit is not compatible across architectures? We don't compile binaries or anything like that, but I reckon the builder, or the start command might have some constraints? Should they?

Is output standalone not an option? how come?

[escherstair]

@icyJoseph I haven't tried because I thought that I would need this.
Do you mean that if I install the node modules with --cpu and then I call next build with a standalone output I could copy the output to my different architecture and it works?

[icyJoseph]

Right, because the problem would be either, at install or postinstall.

• next build uses SWC, which is itself a native binary - it has to match the builder arch - but it only outputs JS - you don't need it at runtime.
• the rest of the next build process, outputs other static files that do not depend on architecture (HTML, JS, CSS, etc)
• What does depend on the builder arch are certain packages/dependencies, for example sharp

Perhaps you'd need to install the versions for the architectures you need? With pnpm you'd use this: https://pnpm.io/settings#supportedarchitectures - this should include the architectures you want to deploy to.

So then standalone would include them all - I believe - so when you boot your app within a box with a different arch, you have and can reference the proper binaries.

[escherstair]

I tried and it seems ok!
I'm going to do deep test in the next few weeks, but I think that in case of architecture mismatching nothing would run.
Anm, basically, the application runs.

[icyJoseph]

Nice~ do consider changing this to a help type and mark it as answered then. Happy to keep on tracking and helping.