Maintaining protobuf specs

The Penumbra project dynamically generates code for interfacing with gRPC. The following locations within the repository are relevant:

  • proto/proto/penumbra/**/*.proto, the developer-authored spec files
  • proto/src/gen/*.rs, the generated Rust code files
  • tools/proto-compiler/, the build logic for generated the Rust code files

We use buf to auto-publish the protobuf schemas at, and to generate Go and Typescript packages. The Rust code files are generated with our own tooling, located at tools/proto-compiler.

Our custom tooling for generating the Rust files will also shape the Serde implementations of the derived Rust types to have more favorable JSON output (such as rendering addresses as Bech32-encoded strings).

Installing protobuf

Obtain the most recent pre-compiled binary from the protoc website. After installing, run protoc --version and confirm you’re running at least 3.21.8 (or newer). Don’t install protoc from package managers such as apt, as those versions are often outdated, and will not work with Penumbra.

Building protobuf

Switch to the proto-compiler directory and run the tool:

cd tools/proto-compiler
cargo run

Then run git status to determine whether any changes were made. The build process is deterministic, so regenerating multiple times from the same source files should not change the output. A possible exception to this rule is if prost makes a superficial change to the output that isn’t substantive.

If the generated output would change in any way, CI will fail, prompting the developer to commit the changes.