Consider an icu version of `aot-deps`

[richlander]

This recent issue got me thinking that we should consider providing an icu version of aot-deps and maybe even runtime-deps.

dotnet/core#8663

Today, we don't provide an ICU version of Alpine since we'd need two duplicate branches of images. This policy makes sense. When we think solely of self-contained, which all native aot apps are, then having an ICU image makes a lot more sense and avoids the need for the chisel tool. I see the cost/benefit tradeoff for ICU images being quite different (and more compelling) for aot-deps and consider same for runtime-deps (maybe later).

[mthalman]

[Triage]

• The UX for dealing with the installation of additional packages in chiseled scenarios is not great. It's quite verbose, requires copying from some sort of sample, and is generally not easy to understand.
• Adding a new image type (repository) is not something we want to do without very good reason as it increases the burden of maintenance on the production side and adds to the concept count that users need to consider.
• There are two aspects of the UX of installing additional packages in chiseled scenarios that need to be improved:
  • Acquistion of the chisel tool
  • Installation of the package and subsequent cleanup
• One argument is that we should invest more in improving the UX of installing additional packages. That is a goal anyway as it will be applicable to more scenarios than just the need for icu. Ideally, the UX would be improved to the point where the need of an icu-specific image type goes away. In that case, we could always discontinue that image type for the next major .NET version.

[jkotas]

ICU is written in C++ and brings in dependency on C++ runtime.

Is the C++ runtime the only thing that differentiates between aot-deps and runtime-deps? If it is the case, aot-deps w/ ICU is going to be identical to runtime-deps w/ ICU.

[richlander]

Great observation.

See runtime-deps:chiseled -> https://github.com/dotnet/dotnet-docker/blob/main/src/runtime-deps/8.0/jammy-chiseled/amd64/Dockerfile

You can see that we went the "Alpine route" and removed (didn't add) ICU.

I am now thinking that we should do the following:

• aot-deps:chiseled -- no ICU
• runtime-deps:chiseled has ICU

This will have a couple advantages:

• Much higher number of users can switch to chiseled (in CoreCLR land) from regular Ubuntu w/no fanfare.
• We have ICU and non-ICU variants covered.

We made this ICU decision before .NET 7 shipped. It was an obvious decision at the time and then we forgot about it and didn't revisit it. W/more information available, this seems like a better plan. If folks want CoreCLR + smaller, then got aot-deps + self-contained + trimming.

Works?

[MichaelSimons]

Works?

What percentage of apps can utilize Native AOT? I has the understanding that there are feature gaps that prevent all apps from using it.

[richlander]

Good question, but that's not what I meant.

Much higher number of users can switch to chiseled (in CoreCLR land) from regular Ubuntu w/no fanfare.

I meant that our goal is to enable a high % of apps that are currently targeting Ubuntu or Debian (with CoreCLR) to switch to our chiseled images, still with CoreCLR. Adding ICU back will help with that. It also means we don't have to document take-backs. We never really discussed that. To be clear, Alpine users can switch to, but that's outside this discussion.