A digression thanks to Sal Rashid who’s exploring WASM filters w/ Envoy. The documentation is sparse but: How to write WASM filters for Envoy… There is a Rust SDK but it’s not documented: proxy-wasm-rust-sdk I found two useful posts by Rustaceans who were able to make use of it: Extending Envoy with WASM and Rust Extending Istio with Rust and WebAssembly Here’s my simple use of the SDK’s examples.

Following on from waPC & Protobufs, I can now remotely invoke (arbitrary) WASM functions: Client: The logging isn’t perfectly clear but, the client gets (a previously added) WASM binary from the server (using the SHA-256 of the WASM binary as a unique identifier). The result includes metadata that includes a protobuf descriptor of the WASM binary’s functions. The descriptor defines gRPC services (that represent the WASM functions) with input (parameters) and output (results) messages.

Google has a new Golang Protobuf API, APIv2 (google.golang.org/protobuf) superseding APIv1 (github.com/golang/protobuf). If your code is importing github.com/golang/protobuf, you’re using APIv2. Otherwise, you should consult with the docs because Google reimplemented APIv1 atop APIv2. One challenge this caused me, as someone who does not use protobufs and gRPC on a daily basis, is that gRPC (code-generation) is being removed from the (Golang) protoc-gen-go, the Golang plugin that generates gRPC service bindings.