serverless-webpack

What is serverless-webpack?

The serverless-webpack npm package is a Serverless Framework plugin that integrates Webpack to optimize and bundle your Serverless functions. It allows you to use Webpack's powerful features like tree shaking, code splitting, and module resolution to create optimized and efficient Serverless applications.

What are serverless-webpack's main functionalities?

Bundling

This feature allows you to bundle your Serverless functions using Webpack. The provided code sample demonstrates a basic Webpack configuration for bundling a handler.js file.

module.exports = {
  entry: './handler.js',
  target: 'node',
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: 'babel-loader'
      }
    ]
  },
  output: {
    libraryTarget: 'commonjs2',
    path: path.resolve(__dirname, '.webpack'),
    filename: 'handler.js'
  }
};

Tree Shaking

Tree shaking is a feature that eliminates dead code from your bundle. The code sample shows how to enable tree shaking by setting the mode to 'production' and using the 'usedExports' optimization option.

module.exports = {
  mode: 'production',
  entry: './handler.js',
  optimization: {
    usedExports: true
  },
  output: {
    libraryTarget: 'commonjs2',
    path: path.resolve(__dirname, '.webpack'),
    filename: 'handler.js'
  }
};

Code Splitting

Code splitting allows you to split your code into separate bundles, which can be loaded on demand. The code sample demonstrates how to configure Webpack to create separate bundles for 'handler.js' and 'anotherModule.js'.

module.exports = {
  entry: {
    handler: './handler.js',
    anotherModule: './anotherModule.js'
  },
  output: {
    filename: '[name].js',
    path: path.resolve(__dirname, '.webpack')
  }
};

Module Resolution

Module resolution allows you to create aliases for directories, making it easier to import modules. The code sample shows how to create an alias '@utils' for the 'src/utils/' directory.

module.exports = {
  resolve: {
    alias: {
      '@utils': path.resolve(__dirname, 'src/utils/')
    }
  },
  entry: './handler.js',
  output: {
    libraryTarget: 'commonjs2',
    path: path.resolve(__dirname, '.webpack'),
    filename: 'handler.js'
  }
};

Other packages similar to serverless-webpack

serverless-bundle

The serverless-bundle package is a Serverless Framework plugin that uses Webpack and Babel to bundle your functions. It simplifies the setup process by providing a pre-configured Webpack and Babel setup. Compared to serverless-webpack, serverless-bundle is more opinionated and easier to set up, but offers less flexibility for custom configurations.

serverless-plugin-typescript

The serverless-plugin-typescript package is a Serverless Framework plugin that compiles your TypeScript code to JavaScript before deployment. It uses the TypeScript compiler (tsc) instead of Webpack. Compared to serverless-webpack, it is more focused on TypeScript projects and does not offer the same level of optimization and bundling features.

serverless-esbuild

The serverless-esbuild package is a Serverless Framework plugin that uses esbuild to bundle and minify your functions. Esbuild is known for its speed and efficiency. Compared to serverless-webpack, serverless-esbuild offers faster build times but may lack some of the advanced features and plugins available in Webpack.

README

Serverless Webpack

A Serverless v1.0 plugin to build your lambda functions with Webpack.

This plugin is for you if you want to use the latest Javascript version with Babel; use custom resource loaders; try your lambda functions locally and much more!

Install

npm install serverless-webpack

Add the plugin to your serverless.yml file:

plugins:
  - serverless-webpack

Configure

By default the plugin will look for a webpack.config.js in the service directory. In alternative you can specify a different file or configuration in the serverless.yml with:

custom:
  webpack: ./folder/my-webpack.config.js

An base Webpack configuration might look like this:

// webpack.config.js

module.exports = {
  entry: './handler.js',
  target: 'node',
  module: {
    loaders: [ ... ]
  }
};

Note that, if the output configuration is not set, it will automatically be generated to write bundles in the .webpack directory. If you set your own output configuration make sure to add a libraryTarget for best compatibility with external dependencies:

// webpack.config.js

module.exports = {
  // ...
  output: {
    libraryTarget: 'commonjs',
    path: '.webpack',
    filename: 'handler.js', // this should match the first part of function handler in serverless.yml
  },
  // ...
};

By default, the plugin will try to bundle all dependencies. However, you don't want to include all modules in some cases such as selectively import, excluding builtin package (ie: aws-sdk) and handling webpack-incompatible modules.

In this case you might add external modules in Webpack externals configuration. Those modules can be included in the Serverless bundle with the webpackIncludeModules option in serverless.yml:

// webpack.config.js
var nodeExternals = require('webpack-node-externals')

modules.export = {
  // we use webpack-node-externals to excludes all node deps.
  // You can manually set the externals too.
  externals: [nodeExternals()],
}

# serverless.yml
custom:
  webpackIncludeModules: true # enable auto-packing of external modules

All modules stated in externals will be excluded from bundled files. If an excluded module is stated as dependencies in package.json, it will be packed into the Serverless artifact under the node_modules directory.

By default, the plugin will use the package.json file in working directory, If you want to use a different package conf, set packagePath to your custom package.json. eg:

# serverless.yml
custom:
  webpackIncludeModules:
    packagePath: '../package.json' # relative path to custom package.json file.

Note that only relative path is supported at the moment.

You can find an example setups in the examples folder.

Usage

Automatic bundling

The normal Serverless deploy procedure will automatically bundle with Webpack:

• Create the Serverless project with serverless create -t aws-node
• Install Serverless Webpack as above
• Deploy with serverless deploy

Simulate API Gateway locally

To start a local server that will act like the API Gateway use the following command. Your code will be reloaded upon change so that every request to your local server will serve the latest code.

serverless webpack serve

Options are:

• --port or -p (optional) The local server port. Defaults to 8000

The serve command will automatically look for the local serverless.yml and serve all the http events. For example this configuration will generate a GET enpoint:

functions:
  hello:
    handler: handler.hello
    events:
      - http:
          method: get
          path: hello

Run a function locally

To run your bundled functions locally you can:

serverless webpack invoke --function <function-name>

Options are:

• --function or -f (required) is the name of the function to run
• --path or -p (optional) is a JSON file path used as the function input event

Run a function locally on source changes

Or to run a function every time the source files change use watch:

serverless webpack watch --function <function-name> --path event.json

Options are:

• --function or -f (required) is the name of the function to run
• --path or -p (optional) is a JSON file path used as the function input event

Bundle with webpack

To just bundle and see the output result use:

serverless webpack --out dist

Options are:

• --out or -o (optional) The output directory. Defaults to .webpack.

Example with Babel

In the examples folder there is a Serverless project using this plugin with Babel. To try it, from inside the example folder:

• npm install to install dependencies
• serverless webpack run -f hello to run the example function