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bigband-cli - Backstage Plugins in any language using WebAssembly

Generate Backstage Frontend plugins and Backend plugins with bigband-cli!

How it works

This plugin works by taking in a WebAssembly binary file compiled from your favorite $LANGUAGE, and generating a JS-based Backstage plugin out of it, and installed into your Backstage installation.

Quickstart

First, install the bigband-cli CLI into your javascript project:

npm install -D bigband-cli

Note

Here we use a project-local, development-only installation -- you can also install bigband globally if you'd like.

Once the CLI is installed, you can point it at a WebAssembly binary and supply some options to build a Backstage plugin:

bigband generate \
    --plugin-type frontend \
    --plugin-id your-plugin \
    --wasm-binary path/to/your/plugin.wasm \
    --output-dir output \
    --backstage-dir path/to/your/backstage/code

Context

What is WebAssembly?

WebAssembly is a new compilation target (think Java bytecode, Python bytecode, x86_64 or arm64 machine code) for programming languages. WebAssembly comes with many features:

  • Isolated by default (at the most basic level, all your computation has access to is numbers and numeric operations)
  • Runs everywhere (thanks to it's extremely reduced data set)
  • Near-native execution speed (thanks to many compiler optimizations and painstaking design)

While WebAssembly was originally designed to run on the web, thanks to extensive work done by the Bytecode Alliance WebAssembly has been generalized so that it can run on in web browsers and server or desktop contexts.

By using a a standards-compliant runtime like wasmtime, you can:

  1. Write code in your favorite $LANGUAGE
  2. Compile that code to an alternate WebAssembly speicific compilation target (ex. wasm32-wasi, as opposed to amd64, arm64, Python bytecode, Java bytecode)
  3. Run wasmtime from inside an existing program or separately to execute your WebAssembly

How does WebAssembly integrate with Backstage?

Since Backstage plugins are normally written in Javascript, this CLI takes the approach of tranpsiling WebAssembly to Javascript, and bundling that generated Javascript into the form a Backstage plugin should take.

The form this requires is quite different for frontend and backend apps, but essentially:

  • Frontend apps are required to produce the JS code that powers React components which will be served and used
  • Backend apps are required to perform functionality for incoming requrests to registered endpoints

To effectively create a frontend or backend application, we use the [WebAssembly Interface Types (WIT)][wit] standard to make the requirements for these two types of plugins concrete. See the two related WIT files (which should be quite readable):

Build from source

To build the code in this repository:

npm run build

Run from source

If you wanted to build the example backend of the examples from source, you could run the following command to use the local build:

export WASM_BINARY_PATH=$(realpath ../../examples/rust/frontend-plugin/target/wasm32-wasi/debug/backstage_rust_frontend_plugin.wasm)
export BACKSTAGE_DIR=/path/to/your/backstage/dir
node dist/index.mjs generate \
    --plugin-type frontend \
    --plugin-id example-frontend \
    --wasm-binary $WASM_BINARY_PATH \
    --output-dir /tmp/output-frontend \
    --backstage-dir $BACKSTAGE_DIR

Warning

Note that the code above uses debug builds of the binaries -- you may want to use release builds for smaller and faster binaries

To run the backend example, you can run a similar command, pointing at a separately built binary:

export WASM_BINARY_PATH=$(realpath ../../examples/rust/backend-plugin/target/wasm32-wasi/debug/backstage_rust_backend_plugin.wasm)
export BACKSTAGE_DIR=/path/to/your/backstage/dir
node dist/index.mjs generate \
    --plugin-type backend \
    --plugin-id example-backend \
    --wasm-binary $WASM_BINARY_PATH \
    --output-dir /tmp/output-backend \
    --backstage-dir $BACKSTAGE_DIR