The Infernal Machine - An AWS Lambda Custom Runtime for Haskell

Since AWS released custom runtimes, you don't need to play any dirty tricks to get your Haskell programs running on AWS Lambda. Just call an infernal entrypoint in your main function, statically link your binary, and zip it up right. If you want to use your Lambda to serve API Gateway requests with an existing WAI app, there's a wrapper for that too.

How to write your own Lambda

The easiest way to get started is to use the provided stack template and follow the generated README:

stack new my-haskell-lambda https://github.com/ejconlon/infernal/raw/master/stack-template.hsfiles

Otherwise you can assemble things yourself:

• See Makefile, stack.yaml, and package.yaml in demo for the right options to build your program
  • statically-linked
  • in a Docker container
  • zipped the right way
  • with some deps temporarily not in Stackage
• Import Infernal in your Main module and use runSimpleLambda to run your handler
• See demo/sam/test.sh if you want to use aws-sam-cli to test your program locally
• Deploy to AWS with your tool of choice (Serverless, Terraform + awscli, AWS console, etc)

Development

The libs subdir has the library, and demo has a small example application. They are separate stack projects because the demo needs to be built with Docker on OSX. See the Brewfile for test deps on OSX. Basically, if you have stack, docker, and aws-sam-cli installed, you can run make integration-test to check a few cases. When making changes to the stack template, run make template-test.

Prior work

Thanks to Nick Tchayka and Theam for aws-lambda-haskell-runtime. Between reading their implementation and the official documentation it was pretty easy to get this working. aws-lambda-haskell-runtime is a great library but I had trouble combining the TemplateHaskell entrypoint with some custom startup logic.

Also thanks to Alexey Kotlyarov and Seek for serverless-haskell. Their API Gateway definitions are very useful, and I am grateful to not have to hand-roll JSON codecs. I did not introduce the library as a dependency because I wanted to simplify the definitions a bit and avoid multiple amazonka dependencies not available in Stackage.

You can find copies of both licenses in the licenses directory.

TODO

• Set up CI
• Add to Stackage
• Add other standard events