Serverless Plugin: Multiple Responses

What is it?

This is a plugin for the Serverless framework intended to address the issues outlined at https://github.com/serverless/serverless/issues/2046 (and in my - jthomerson - comments there).

Once that feature is supported in SLS this plugin will no longer be needed or maintained.

How do I use it?

The basic principle is that instead of adding a response attribute to your HTTP event config, you will add a responses attribute.

The responses attribute is a key/value pair where the key is the status code of the response (e.g. 200, 404, etc). The value can be:

• false - which means "remove the default response configured by SLS (or another plugin) for this response code"
• an object with the following attributes:
  • headers - just the same as the SLS headers attribute
  • templates - similar to request templates, this is keyed by the response content type
  • properties - any other properties to directly add to the CloudFormation template for this API method
    • typically this is used to add SelectionPattern for the error responses

NOTE: leaving one response without a selection pattern attribute makes it the default response.

Below we will show two examples: a standard example where 200 is what your function returns for a successful completion, and another example where it needs to return a 302 as its default (non-error) response. The 302 response example would be used if your were building a bit.ly-like endpoint, for example.

# I recommend using variables to define your responses since they tend
# to be the same across all of your API gateway functions, but you
# certainly don't have to.
custom:
   defaultRegion: us-east-1
   region: ${opt:region, self:custom.defaultRegion}
   stage: ${opt:stage, env:USER}
   standardRequest:
      template:
         application/json: ${file(templates/standard-request.tpl)}
   standardResponseHeaders:
      'Access-Control-Allow-Origin': "'*'"
      'Content-Type': 'integration.response.body.headers.Content-Type'
      'Expires': 'integration.response.body.headers.Expires'
      'Cache-Control': 'integration.response.body.headers.Cache-Control'
      'Pragma': "'no-cache'"
   standardResponseTemplate: "$input.path('$.body')"
   errorResponseHeaders:
      'Access-Control-Allow-Origin': "'*'"
      'Expires': "'Thu, 19 Nov 1981 08:52:00 GMT'"
      'Cache-Control': "'no-cache, max-age=0, must-revalidate'"
      'Pragma': "'no-cache'"
   errorResponseTemplate: "$input.path('$.errorMessage')"
   # Here we are defining what would be under "responses" in your HTTP event
   # if you were not using the custom variables.
   standardResponses:
      200:
         headers: ${self:custom.standardResponseHeaders}
         templates:
            'application/json;charset=UTF-8': ${self:custom.standardResponseTemplate}
      404:
         headers: ${self:custom.errorResponseHeaders}
         templates:
            'application/json;charset=UTF-8': ${self:custom.errorResponseTemplate}
         properties:
            SelectionPattern: '.*\"status\":404.*'
      500:
         headers: ${self:custom.errorResponseHeaders}
         templates:
            'application/json;charset=UTF-8': ${self:custom.errorResponseTemplate}
         properties:
            SelectionPattern: '.*\"status\":500.*'
   redirectResponses:
      # Since we want to return 302 upon a successful completion, we remove the
      # built-in default of 200
      200: false
      302:
         headers:
            Location: "integration.response.body.headers.Location"
         templates:
            'application/json;charset=UTF-8': "$input.path('$.body')"
            'text/html;charset=UTF-8': "$input.path('$.body')"
      404:
         headers: ${self:custom.errorResponseHeaders}
         templates:
            'application/json;charset=UTF-8': "$input.path('$.body')"
            'text/html;charset=UTF-8': "$input.path('$.body')"
         properties:
            SelectionPattern: '.*\"status\":404.*'
      500:
         headers: ${self:custom.errorResponseHeaders}
         templates:
            'application/json;charset=UTF-8': "$input.path('$.body')"
            'text/html;charset=UTF-8': "$input.path('$.body')"
         properties:
            SelectionPattern: '.*\"status\":500.*'

# Tell your service that you want to use this plugin:
# (you'll need to `npm install` it first)
plugins:
   - serverless-plugin-multiple-responses

# In the function's http event configuration you see where
# we have `responses` instead of the normal `response`.
functions:
   ping:
      name: ${self:service}-${self:provider.stage}-ping
      handler: src/ping/Ping.handler
      memorySize: 128
      timeout: 2
      events:
         - http:
            method: GET
            path: ping
            request: ${self:custom.standardRequest}
            responses: ${self:custom.standardResponses}
   redirector:
      name: ${self:service}-${self:provider.stage}-redirector
      handler: src/redirector/Redirector.handler
      memorySize: 128
      timeout: 2
      events:
         - http:
            method: GET
            path: redirector
            request: ${self:custom.standardRequest}
            responses: ${self:custom.redirectResponses}

How do I contribute?

Easy! Pull requests are welcome! Just do the following:

• Clone the code
• Install the dependencies with npm install
• Create a feature branch (e.g. git checkout -b my_new_feature)
• Make your changes and commit them with a reasonable commit message
• Make sure the code passes our standards with grunt standards
• Make sure all unit tests pass with npm test

Our goal is 100% unit test coverage, with good and effective tests (it's easy to hit 100% coverage with junk tests, so we differentiate). We will not accept pull requests for new features that do not include unit tests. If you are submitting a pull request to fix a bug, we may accept it without unit tests (we will certainly write our own for that bug), but we strongly encourage you to write a unit test exhibiting the bug, commit that, and then commit a fix in a separate commit. This greatly increases the likelihood that we will accept your pull request and the speed with which we can process it.

License

This software is released under the MIT license. See the license file for more details.