Ferris Says

This folder contains a simple WebAssembly component written in Rust, which responds with a version of cowsay tailored to Rustaceans (users of Rust).

Prerequisites

• cargo 1.80
• wash 0.29.0

Building

bash

wash build

Running with wasmCloud

Ensuring you've built your component with wash build, you can launch wasmCloud and deploy the full hello world application with the following commands. Once the application reports as Deployed in the application list, you can use wash call to call the exported function invoke.

shell

wash up -d
wash app deploy ./wadm.yaml
wash call ferris_says-ferris_says wasmcloud:example-ferris-says/invoke.say

You should see output that looks like the following:

 _______________________________
< Hello fellow wasmCloud users! >
 -------------------------------
        \
         \
            _~^~^~_
        \) /  o o  \ (/
          '_   -   _'
          / '-----' \

Adding Capabilities

Want to go beyond this simple demo?

To learn how to extend this example with additional capabilities, see the Adding Capabilities section of the wasmCloud documentation.

BONUS: Using the "system" clock in a WebAssembly context

When you use the say() export with this component, it uses the system clock, provided by the Rust standard library (SystemTime) and made available via WASI clocks interface.

Time, and computerized clocks are complicated, and "base" WebAssembly has no concept of a clock, which is where the WASI clocks interface steps in. That said, it's not that simple -- wasmtime and other implementers of the WASI spec must choose what implementation of a clock to give you.

While somewhat unexpected, giving an accurate clock can be unsafe. Giving untrusted programs access to a very accurate clock on a system can make timing attacks possible or make for easier fingerprinting, so some may choose to insert some jitter into the clock that is made available to WebAssembly binaries at runtime.

wasmCloud chooses to expose the wasmtime generated bindings for the system clock, which may change in the future, but it's important to keep in mind that these discrepancies are present, and answers you get from the SystemTime may be slightly inconsistent (in a bounded way) with "real time".