wasi-grpc

Enables gRPC clients to work inside Spin components using wasi-hyperium and the spin-rust-sdk.

Spin is a fast, secure WebAssembly framework for serverless apps. This project extends Spin's capabilities by enabling components to make outbound gRPC requests, bridging the gap between Wasm sandboxing and modern microservice communication.

🚀 Features

• 🧩 gRPC over HTTP/2 support inside Spin apps
• 🔐 Compatible with the Spin sandbox security model
• 🦀 Built with wasi-hyperium and tonic
• 🌍 Works with most standard gRPC services
• 🧪 Great for calling internal microservices or public gRPC APIs from Spin

🛠️ Usage

1. Add required dependencies to your Cargo.toml

[dependencies]
anyhow = "1"
futures = "0.3.28"
prost = "0.13.5"
wasi-grpc = "0.1.0"
spin-sdk =  "4.0.0"
tonic = { version = "0.13.1", features = ["codegen", "prost", "router"], default-features = false}

2. Generate gRPC client code with tonic-build

In build.rs:

fn main() {
    tonic_build::configure()
        .type_attribute("routeguide.Point", "#[derive(Hash)]")
        .build_transport(false)
        .compile_protos(&["route_guide.proto"], &[""])
        .unwrap();
}

And in Cargo.toml:

[build-dependencies]
tonic-build = { version = "0.13.1", features = ["prost"] }

3. Call your gRPC service from a Spin component

let endpoint = WasiGrpcEndpoint::new(endpoint_uri);
let mut client = RouteGuideClient::new(endpoint);

let response = client.get_feature(Request::new(Point {
    latitude: 409_146_138,
    longitude: -746_188_906,
})).await?;

🔒 Spin Notes

This project assumes execution in a Spin-compliant runtime that allows outbound networking via Spin's capability-based model. Ensure your spin.toml includes the appropriate allowed_outbound_hosts granting outbound access to your gRPC service's endpoint.

Writing gRPC servers

This repo also contains the wasi-grpc-server crate, which provides a helper for writing gRPC services as wasi:http handlers. See the crate documentation for more information.