Instructions on getting warmup to work with serverless-webpack

I preface this with the fact that I’m a webpack newbie so this may be suboptimal.

If using the serverless-webpack plugin then you need to make some changes to webpack.config.js to get serverless-plugin-warmup to work.

1. Add a new chunk for warmup with the specific path that the warmup plugin uses.
2. Add an output section as per above. This ensures that the warmup handler is appears in the bundle at the same path as it would have originally.

For example:

  entry: {
    handler: [/* possibly other entry points like babel-polyfill, ... */ './handler.js'],
    '_warmup/index': './_warmup/index.js',
  },
  output: {
    libraryTarget: 'commonjs',  // <- as per serverless-webpack README
    path: '.webpack',
    filename: '[name].js',
  },

An issue with this setup is that serverless webpack invoke no longer works because _warmup does not exist then.

Another potential issue is the reliance on the _warmup/index.js path not changing.

[mikestaub]

@damonmaria I simply copy the whole _warmup dir with copy-webpack-plugin like so:

plugins: [new CopyWebpackPlugin({ from: '_warmup', to: '_warmup' })],

[lucasklaassen]

For anyone else that finds this thread, the following webpack.config.js works for me now:

const nodeExternals = require('webpack-node-externals');
const path = require('path');
const slsw = require('serverless-webpack');

module.exports = {
  entry: slsw.lib.entries,
  target: 'node',
  externals: [nodeExternals()],
  output: {
    libraryTarget: 'commonjs',
    path: path.resolve(__dirname, '.webpack'),
    filename: '[name].js' // this should match the first part of function handler in serverless.yml
  },
  module: {
    loaders: [
      {
        test: /\.jsx?$/,
        exclude: /node_modules/,
        loaders: ["babel-loader"]
      },
      {
        test: /\.json$/,
        loader: 'json-loader'
      }
    ]
  }
};

serverless: 1.24.1 serverless-plugin-warmup: 3.3.0-rc.1 serverless-webpack: 4.0.0 webpack: 4.0.0