Easegress AssemblyScript SDK

• Easegress AssemblyScript SDK
  • Prerequisites
  • Local Development
  • Deploy and execute

This is the AssemblyScript SDK for Easegress, it can be used to extend the ability of Easegress.

Prerequisites

The following assumes that a recent version of Git, Node.js and its package manager npm are installed. Basic knowledge about writing and working with TypeScript modules, which is very similar, is a plus.

Local Development

1. Clone this repo to somewhere on disk.

2. Switch to a new directory and initialize a new node module:

npm init

3. Install the AssemblyScript compiler using npm, assume that the compiler is not required in production and make it a development dependency:

npm install --save-dev assemblyscript

4. Once installed, the compiler provides a handy scaffolding utility to quickly set up a new AssemblyScript project, for example in the directory of the just initialized node module:

npx asinit .

5. Add --use abort= to the end asc assembly/index.ts ... command in package.json, for example,

Before add --use abort=:

...
    "scripts": {
        "test": "node tests",
        "asbuild:debug": "asc assembly/index.ts --target debug",
        "asbuild:release": "asc assembly/index.ts --target release",
        "asbuild": "npm run asbuild:debug && npm run asbuild:release",
        "start": "npx serve ."
    },
...

After add --use abort=:

...
    "scripts": {
        "test": "node tests",
        "asbuild:debug": "asc assembly/index.ts --target debug --use abort=",
        "asbuild:release": "asc assembly/index.ts --target release --use abort=",
        "asbuild": "npm run asbuild:debug && npm run asbuild:release",
        "start": "npx serve ."
    },
...

6. Copy this into assembly/index.ts, note to replace PATH_TO_SDK_REPO with the path in the first step:

// As required by Easegress, these functions must be exported
// Use relative path here, like ../../easegress-assemblyscript-sdk/easegress/proxy
export * from 'PATH_TO_SDK_REPO/easegress/proxy'

// Use relative path here, like ../../easegress-assemblyscript-sdk/easegress
import { Program, request, LogLevel, log, registerProgramFactory } from 'PATH_TO_SDK_REPO/easegress'

class AddHeaderAndSetBody extends Program {
    constructor(params: Map<string, string>) {
        super(params)
    }

    run(): i32 {
        super.run()
        let v = request.getHeader( "Foo" )
        if( v.length > 10 ) {
            log( LogLevel.Warning, "The length of Foo is greater than 10" )
        }
        if( v.length > 0 ) {
            request.addHeader( "Wasm-Added", v )
        }
        request.setBody( String.UTF8.encode("I have a new body now") )
        return 0
    }
}

registerProgramFactory((params: Map<string, string>) => {
    return new AddHeaderAndSetBody(params)
}

7. Build with this command

npm run asbuild

If everything is right, debug.wasm (the debug version) and release.wasm (the release version) will be generated at the build folder.

Deploy and execute

Please refer the documentation of WasmHost for deploying and executing the compiled Wasm code.