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README.md

HTTP Middleware

Making custom WebAssembly ABIs requires rigor, discipline, and significant time. The complexity of testing, versioning, backward compatibility, data serialization, threading, multi-language support, and ongoing maintenance is easy to underestimate.

This example shows how products and platforms can use waPC and Apex to create plugin systems for WebAssembly-based HTTP middleware. We use Apex to define interfaces and generate language-specific code for both the middleware component and host process.

Installation

Requirements:

  • Go 1.19+ - The Go programming language
  • TinyGo 0.25+ - Compiles Go programs to WebAssembly and microcontrollers
  • Apex CLI - An interface description language for modeling any software
  • The waPC code generation module

To install the waPC code generation module:

apex install @wapc/codegen

Building

Use this command to run the code generator from the command line:

apex generate

If you open this project in VS Code, there should be a task to run in the background and watch middleware.apexlang for changes and rerun the code generators.

The only file you need to edit is pkg/middleware.go.

Compile the TinyGo version of the module:

make

Compile the AssemblyScript version of the module:

npm install
npm run build

Running

Now you can run a simple fasthttp / fasthttprouter example that loads the WebAssembly middleware component located at build/middleware.wasm. Optionally, you can edit main.go to point to the AssemblyScript file at build/middleware-as.wasm.

go run main.go

From another terminal, test the component with cURL.

curl -i -L http://localhost:8181
HTTP/1.1 301 Moved Permanently
Server: fasthttp
Date: Wed, 21 Sep 2022 20:11:48 GMT
Content-Length: 0
Location: http://localhost:8181/hello/

HTTP/1.1 200 OK
Server: fasthttp
Date: Wed, 21 Sep 2022 20:11:48 GMT
Content-Type: text/plain
Content-Length: 23

Hello from WebAssembly!