Using Viceroy and Alternative Hosts

Viceroy

Viceroy is a local testing environment that mimics the Fastly Compute@Edge Wasm host to enable quick testing locally. It is built into the Fastly CLI and can be used on a stand-alone basis.

See the Developer Guide for more information including constraints and limitations of the server.

Note: While Fastly now uses the Wasmtime WebAssembly runtime, Viceroy still uses Lucet. Bcause of this, there will be some minor differences in how they operate.

Alternatives

• fastlike by Alex Vidal provides an alternative host implementation using wasmtime, which is the successor project to Lucet.
• wazero is a zero dependency WebAssembly runtime in Go for which there is interest to implement the Fastly ABI.