Extending Kubernetes API in-process

Project structure:

• ext-simple-pod: Wasm module that implements a simple controller to spawn pods
• ext-memcached: Wasm module that implements the operator-sdk Memcached sample
• kube-rs: Hacked https://github.com/clux/kube-rs to run inside the module
• kube-rs-host: Hacked https://github.com/clux/kube-rs to use inside the host
• rust-host: The host running wasm modules

Build

To build the memcached example controller:

cd ext-memcached
cargo build --target wasm32-wasi --release

Assuming you have a Kubernetes cluster up and running and you have an admin access to it configured in your local environment, deploy the CRD:

kubectl apply -f ext-memcached/crd.yaml

Now, copy in a directory (eg rust-host/compiled_mods) the compiled module and the manifest the host needs to identify the abi to use:

mkdir rust-host/compiled_mods
cp ext-memcached/memcached.yaml rust-host/compiled_mods
cp ext-memcached/wasm32-wasi/release/memcached.wasm rust-host/compiled_mods

To compile and run the host:

cd rust-host
RUST_LOG=rust_host=debug,cranelift=warn,kube=debug cargo +nightly run compiled_mods

Now you can create the Memcached CR with:

kubectl apply -f ext-memcached/cr.yaml