Serverless Haskell

Deploying Haskell code onto AWS Lambda using Serverless.

Requirements

• AWS account
• Stack
• NPM
• Docker unless running on a Linux host

Usage

• Create a Stack package for your code:

  stack new mypackage
  

  LTS 9 and 10 are supported, older versions are likely to work too but untested.

• Initialise a Serverless project inside the Stack package directory and install the serverless-haskell plugin:

  cd mypackage
  npm init .
  npm install --save serverless serverless-haskell
  

• Create serverless.yml with the following contents:

  provider:
    name: aws
    runtime: nodejs6.10
  
  functions:
    myfunc:
      handler: mypackage.myfunc
      # Here, mypackage is the Haskell package name and myfunc is the executable
      # name as defined in the Cabal file
  
  plugins:
    - serverless-haskell
  

• Write your main function:

  import qualified Data.Aeson as Aeson
  
  import AWSLambda
  
  main = lambdaMain handler
  
  handler :: Aeson.Value -> IO [Int]
  handler evt = do
    putStrLn "This should go to logs"
    print evt
    pure [1, 2, 3]
  

• Use sls deploy to deploy the executable to AWS Lambda. Note: sls deploy function is not supported.

  The serverless-haskell plugin will build the package using Stack and upload it to AWS together with a JavaScript wrapper to pass the input and output from/to AWS Lambda.

  You can test the function and see the invocation results with sls invoke myfunc.

Notes

• sls deploy function is not supported.
• Only AWS Lambda is supported at the moment. Other cloud providers would require different JavaScript wrappers to be implemented.

See AWSLambda for documentation, including additional options to control the deployment.

Testing

• Haskell code is tested with Stack: stack test.
• JavaScript code is linted with eslint.

Integration tests

Integration tests are not run automatically due to the need for an AWS account. To run them manually:

• Ensure you have the required dependencies: curl, jq, NPM and Stack.
• Get an AWS account and add the access credentials into your shell environment.
• Run ./integration-test/run.sh. The exit code indicates success.

Releasing

• Run the integration tests.
• Install bumpversion: pip install bumpversion.
• Run bumpversion major|minor|patch.
• Run git push --tags && git push.