Wasmedge

[vasilvas99]

WASM-based containers in Leda

General

WASM+WASI allows to develop for an abstract machine (WASM) with an abstract system interface (WASI ~ POSIX), compile once and deploy on any architecture/machine that has the appropriate WASM/WASI runtime.

WASMEdge is one such runtime that is lightweight, while supporting wasi-preview1 + some of the extensions provided by wasi-preview2 (e.g. sockets, threads).

Preview2-features are not stable yet (and officially supported by the compiler vendors such as clang, rustc, etc) so they require a lot of library patching/ad hoc solutions.

Therefore, developers are encouraged to limit themselves to WASI-preview1.

Implementation

• LLVM 14 recipes backported from newer poky versions due to meta-clang requirements
• meta-leda now depends on clang-layer
• WASMedge-runtime + wasmedge .so libraries (allows developers to embed wasmedege in their applications) recipe implemented
• crun recipe from openembedded patched to compile with the wasmedge feature (allows developers to run wasm-binaries in OCI containers
• containerd reconfigured to use crun for the io.containerd.runc.v2 API
• meta-clang added to kas-files
• Kanto Container Management configured to work with WASM/WASI containers (see issues section)

Requirements

You now should include meta-clang, since wasm runtimes/compilers generally emit LLVM IR, which is then compiled by the system-specific LLVM to native code. If you use kas, add:

  meta-clang:
    url: https://github.com/kraj/meta-clang
    refspec: kirkstone

ref: https://github.com/eclipse-leda/leda-distro/compare/main...SoftwareDefinedVehicle:leda-distro-fork:wasmedge?expand=1

Test setup

This PR was tested by building from the wasmedge branch of https://github.com/SoftwareDefinedVehicle/leda-distro-fork

Tests

Builds created with this PR should be able to run the container examples from the wasmedge website:

https://wasmedge.org/docs/develop/deploy/cri-runtime/containerd-crun/

The quick-test example you can use to verify everything is correct is to run the "rng generator container" with.

sudo ctr i pull docker.io/wasmedge/example-wasi:latest

sudo ctr run --rm --runc-binary crun --runtime io.containerd.runc.v2 --label module.wasm.image/variant=compat-smart docker.io/wasmedge/example-wasi:latest wasm-example /wasi_example_main.wasm 50000000

Issues

CRUN depends on the top-level runtime providing the module.wasm.image/variant=compat-smart "magic" label for the container to distinguish WASM from "normal"/native containers. This is implemented as annotations in k8s.

Kanto Container Management however, does not seem to implement the labels part of the OCI spec (see The containers.proto file for containerd which requires the labels map to be handled specially by the top-level run-time). My assumption is that since "all" labels should be included in update calls and Kanto does not implement labels as part of its interface, they are never passed to containerd even if they were added in the dockerfile/manually with ctr after the image was pulled.

This limits the applicability of WASM containers in our case.

[stlachev]

LGTM