Serverless-serve NPM

Serverless Serve Plugin

When developing with Serverless deploying functions to AWS after each change might be annoying. This plugin allows you to simulate API Gateway locally, so all function calls can be done on localhost.

Installation

In your Serverless project:

npm install serverless-serve

Then in s-project.json add following entry to plugins array:

"serverless-serve"

E.g. like this:

  plugins: ["serverless-serve"]

And in main project root do:

sls serve start

Options

--prefix -p: Add prefix to the URLs, so your clients will not use http://localhost:1465/ but http://localhost:1465/prefix/ instead. Default: empty

--port -P: Port to listen on. Default: 1465

--stage -s & --region -r: If both are given (or there is only 1 region and stage is given), then endpoint response definition will get the template/variable resolved.

--init -i: Initialization file, for custom initializations. Default: empty. NOTE: please specify relative paths from project root folder, e.g. sls serve start -i ./lib/my_init.js. Init file should export single function taking following parameters:

Serverless object
app object from Express (e.g. to register new routes)
handlers object being map of all function names to info about their respective handlers. Since all handlers are require'd lazily, this plugin exports only path information about handler, in following format:

{
  path: "path/to/be/required",
  handler: "exported-function-name"
}

so this should work: require( handlers[ myFunName ].path )[ handlers[ myFunName ].handler ]( event, context )

Example:

module.exports = function(S, app, handlers){
}

Usage

Just send your requests to http://localhost:1465/ as it would be API Gateway.

Using of this plugin with some tool like Nodemon is advised, so Serverless with restart and reload your local code after every change.

Usage with Babel

Optionaly, your handlers can be required with babel-register. To do so, in your s-project.json file, set options to be passed to babel-register like this:

{
  /* ... */
  "custom": {
    "serverless-serve": {
      "babelOptions": {
        /* Your own options, example: */
        presets: ["es2015", "stage-2"]
      }
    }
  },
  "plugins": ["serverless-serve", /* ... */]
}

To view the full list of babel-register options, click here

Simulation quality

This plugin simulates API Gateway for many practical purposes, good enough for development - but is not a perfect simulator. Specifically, no timeout or memory limits are enforced. Mapping templates and/or error codes are not simulated, either. So are security checks. You will probably find other differences.