WASI overview

Write an extension using WASI.

A WASI extension is a WebAssembly module that implements the WASI interface. The module is loaded by the Suffiks runtime and is used to provide the extension’s functionality.

If you want to write an extension, you can either use on of the existing SDKs, or write your own. If you want to write your own, use the runtime overview page to see all the available runtime functions.

When to use WASI #

WASI is a good choice if your extension mainly modifies the workload’s environment.

It is possible to interact with custom resources, but it’s not as easy or efficient as implementing your own GRPC service.

Suffiks SDKs #

The following SDKs are available:

• Go (TinyGo)
• AssemblyScript

See the respective repositories for more information.

Configuration #

Your extension can use configuration values by defining a config section in your extension, which will be passed to the extension as environment variables.

Documentation #

Your extension can provide documentation by defining your pages as Markdown files in a directory, and add the --docs flag to the extgen wasi publish command.

Memory #

Suffiks need to be able to allocate memory for your extension. Your extension must therefore export the following functions:

• malloc(size uint): Allocate memory.
• free(ptr): Free memory.

Publising your extension #

Your extension must be published to a registry before it can be used.

Suffiks WASI extensions are published as custom OCI images. It’s recommended to use the extgen wasi publish command to publish your extension.

extgen wasi publish will build the image and publish it to the registry specified.

It requires a single argument, which is the path to the generated .wasm file.

The following flags are available:

Example:

extgen wasi publish --tag ${IMAGE} --docs ./docs build/release.wasm

Examples #

See the examples repository for example extensions using the WASI SDKs.