Serverless Webpack

A Serverless v1.x 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, optimize your packaged functions individually and much more!

Highlights

• Configuration possibilities range from zero-config to fully customizable
• Support of serverless package, serverless deploy and serverless deploy function
• Support of serverless invoke local and serverless invoke local --watch
• Integrates with serverless-offline to simulate local API Gateway endpoints
• When enabled in your service configuration, functions are packaged and compiled individually, resulting in smaller Lambda packages that contain only the code and dependencies needed to run the function. This allows the plugin to fully utilize WebPack's Tree-Shaking optimization.

New in V3

• Support for individual packaging and optimization
• Integrate with serverless invoke local (including watch mode)
• Stabilized package handling
• Improved compatibility with other plugins
• Updated examples

For the complete release notes see the end of this document.

Install

$ npm install serverless-webpack --save-dev

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. Alternatively, you can specify a different file or configuration in serverless.yml:

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: [ ... ]
  }
};

serverless-webpack lib export helper

serverless-webpack exposes a lib object, that can be used in your webpack.config.js to make the configuration easier and to build fully dynamic configurations. This is the preferred way to configure webpack - the plugin will take care of as much of the configuration (and subsequent changes in your services) as it can.

Automatic entry resolution

You can let the plugin determine the correct handler entry points at build time. Then you do not have to care anymore when you add or remove functions from your service:

// webpack.config.js
const slsw = require('serverless-webpack');

module.exports = {
  ...
  entry: slsw.lib.entries,
  ...
};

Custom entries that are not part of the SLS build process can be added too:

// webpack.config.js
const _ = require('lodash');
const slsw = require('serverless-webpack');

module.exports = {
  ...
  entry: _.assign({
    myCustomEntry1: './custom/path/something.js'
  }, slsw.lib.entries),
  ...
};

Full customization (for experts)

The lib export also provides the serverless and options properties, through which you can access the Serverless instance and the options given on the command-line.

This enables you to have a fully customized dynamic configuration, that can evaluate anything available in the Serverless framework. There are really no limits.

Samples are: The current stage and the complete service definition. You thereby have access to anything that a Serverless plugin would have access to.

Both properties should be handled with care and should never be written to, as that will modify the running framework and leads to unpredictable behavior!

If you have cool use cases with the full customization, we might add your solution to the plugin examples as showcase.

Output

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`
  },
  // ...
};

Node modules / externals

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's 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')

module.exports = {
  // 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 file, set packagePath to your custom package.json:

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

Note that only relative path is supported at the moment.

Sometimes it might happen that you use dynamic requires in your code, i.e. you require modules that are only known at runtime. Webpack is not able to detect such externals and the compiled package will miss the needed dependencies. In such cases you can force the plugin to include certain modules by setting them in the forceInclude array property. However the module must appear in your service's production dependencies in package.json.

# serverless.yml
custom:
  webpackIncludeModules:
    forceInclude:
      - module1
      - module2

You can find an example setups in the examples folder.

Service level packaging

If you do not enable individual packaging in your service (serverless.yml), the plugin creates one ZIP file for all functions (the service package) that includes all node modules used in the service. This is the fastest packaging, but not the optimal one, as node modules are always packaged, that are not needed by some functions.

Optimization / Individual packaging per function

A better way to do the packaging, is to enable individual packaging in your service:

# serverless.yml
...
package:
  individually: true
...

This will switch the plugin to per function packaging which makes use of the multi-compiler feature of Webpack. That means, that Webpack compiles and optimizes each function individually, removing unnecessary imports and reducing code sizes significantly. Tree-Shaking only makes sense with this approach.

Now the needed external node modules are also detected by Webpack per function and the plugin only packages the needed ones into the function artifacts. As a result, the deployed artifacts are smaller, depending on the functions and cold-start times (to install the functions into the cloud at runtime) are reduced too.

The individual packaging should be combined with the automatic entry resolution (see above).

The individual packaging needs more time at the packaging phase, but you'll get that paid back twice at runtime.

Usage

Automatic bundling

The normal Serverless deploy procedure will automatically bundle with Webpack:

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

Run a function locally

The plugin fully integrates with serverless invoke local. To run your bundled functions locally you can:

$ serverless invoke local --function <function-name>

All options that are supported by invoke local can be used as usual:

• --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
• --data or -d (optional) inline JSON data used as the function input event

❗ The old webpack invoke command has been disabled.

Run a function locally on source changes

Or to run a function every time the source files change use the --watch option together with serverless invoke local:

$ serverless invoke local --function <function-name> --path event.json --watch

Everytime the sources are changed, the function will be executed again with the changed sources. The command will watch until the process is terminated.

If you have your sources located on a file system that does not offer events, you can enable polling with the --webpack-use-polling=<time in ms> option. If you omit the value, it defaults to 3000 ms.

All options that are supported by invoke local can be used as usual:

• --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
• --data or -d (optional) inline JSON data used as the function input event

❗ The old webpack watch command has been disabled.

Usage with serverless-offline

The plugin integrates very well with serverless-offline to simulate AWS Lambda and AWS API Gateway locally.

Add the plugins to your serverless.yml file and make sure that serverless-webpack precedes serverless-offline as the order is important:

  plugins:
    ...
    - serverless-webpack
    ...
    - serverless-offline
    ...

Run serverless offline or serverless offline start to start the Lambda/API simulation.

In comparison to serverless offline, the start command will fire an init and a end lifecycle hook which is needed for serverless-offline and e.g. serverless-dynamodb-local to switch off resources (see below).

You can find an example setup in the examples folder.

If you have your sources located on a file system that does not offer events, e.g. a mounted volume in a Docker container, you can enable polling with the --webpack-use-polling=<time in ms> option. If you omit the value, it defaults to 3000 ms.

Custom paths

If you do not use the default path and override it in your Webpack configuration, you have use the --location option.

serverless-dynamodb-local

Configure your service the same as mentioned above, but additionally add the serverless-dynamodb-local plugin as follows:

  plugins:
    - serverless-webpack
    - serverless-dynamodb-local
    - serverless-offline

Run serverless offline start.

Other useful options

You can reduce the clutter generated by serverless-offline with --dontPrintOutput and disable timeouts with --noTimeout.

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.

Simulate API Gateway locally

❗ The serve command has been removed. See above how to achieve the same functionality with the serverless-offline plugin.

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 invoke local -f hello to run the example function

Provider Support

Plugin commands are supported by the following providers. ⁇ indicates that command has not been tested with that provider.

	AWS Lambda	Apache OpenWhisk	Azure Functions	Google Cloud Functions
webpack	✔︎	✔︎	⁇	⁇
invoke local	✔︎	✔︎	⁇	⁇
invoke local --watch	✔︎	✔︎	⁇	⁇

Release Notes

• 3.1.0

  • Allow filesystem polling in watch mode (--webpack-use-polling) #215
  • Allow forced include of not referenced modules #217
  • Automatically include peer dependencies of used modules #223
  • Show explicit message if the provided webpack config can not be loaded #234
  • Improve examples #227
  • Update 3rd party provider compatibility table #221
  • Added automatic Travis and Coveralls builds to increase stability

• 3.0.0

  • Integrate with serverless invoke local #151
  • Support watch mode with serverless invoke local --watch
  • Stabilized and improved the bundling of node modules #116, #117
  • Improved interoperability with Serverless and 3rd party plugins #173
  • Support individual packaging of the functions in a service #120
  • Allow setting stdio max buffers for NPM operations #185
  • Support bundling of node modules via node-externals whitelist #186
  • Removed the webpack serve command in favor of serverless-offline #152
  • Updated examples #179
  • Added missing unit tests to improve code stability
  • Fixed unit tests to run on Windows #145

• 2.2.2

  • Reverted breaking change introduced in default output config #202

• 2.2.1

  • Restore functionality for Google provider #193

• 2.2.0

  • Allow full dynamic configurations #158
  • Fix a bug that prevented the entries lib export to work with TypeScript #165

• 2.1.0

  • Added support for webpack configuration in TypeScript format #129
  • Fixed bug with serverless-offline exec #154
  • Added unit tests for cleanup. Updated test framework #11
  • Support single function deploy and packaging #107
  • Fixed path exception bug with individual packaging and SLS 1.18 #159

• 2.0.0

  • Support arbitrary Webpack versions as peer dependency #83
  • Support serverless offline start invocation #131
  • Documentation updates #88, #132, #140, #141, #144
  • Print Webpack stats on recompile #127