function-sdk-rust

A Rust SDK for writing Crossplane composition functions.

A composition function is a gRPC server implementing the FunctionRunnerService defined by Crossplane's apiextensions.fn.proto.v1 API. This crate provides:

• proto::v1 - generated protocol types with protojson serde support, plus the tonic gRPC server and client.
• server - a function-spec-compliant runtime: mTLS or insecure serving, gRPC server reflection, the gRPC health service, graceful shutdown, and the standard CLI arguments.
• request, response, resource - helpers for typed function input, context keys, required resources and schemas, credentials, capabilities, results, conditions, readiness, and desired resource updates from any serde::Serialize source.
• logging - JSON-lines logging with a human-readable debug mode.

See the repository for a complete example function.