example

WRT Example Using WASI Logging

This WebAssembly Component demonstrates how to import and use the standard WASI logging interface.

Component Model Features

This example showcases:

• Importing WASI logging interface
• Defining interfaces with WIT (WebAssembly Interface Types)
• Component model implementation using wit-bindgen
• WASI Preview 2 target usage

Building

# Install prerequisites (if not done via `just setup`)
rustup target add wasm32-wasip2

# Build the component (using Justfile is recommended)
just build-example

# Alternatively, build directly with cargo:
cargo build -p example --target wasm32-wasip2

Structure

The example consists of:

• example.wit - Defines interfaces and imports WASI logging
• src/lib.rs - Implements the component using the imported logging
• Example logs messages at different levels during execution

WIT Structure

// Import logging interface
import logging;

// Export our main interface
export example;

The component imports the logging interface and calls it from Rust code whenever it needs to log information. The hello function runs a loop and logs information at each iteration, demonstrating how to use the imported logging functionality.

Testing with WRT

To use this example with WRT, you must provide an implementation for the imported logging interface when instantiating the component.