Slides from a talk on Serverless Haskell at the Melbourne Haskell Users Group meetup, 22nd February 2018

1. Serverless Haskell
Alexey Kotlyarov & David Overton

2. Motivation
● AWS Lambda and the Serverless Framework make it easy to write small
functions and deploy them to the cloud…
● … but not in Haskell
● Aim: to make it as easy to do serverless programming in Haskell as it is in
NodeJS or Python
●

3. What we did
● Serverless Haskell
● Developed over a 3 day Hackathon at SEEK in December 2017
● Consists of
○ A Serverless plugin
○ A Haskell library

4. Serverless plugin
● Provides a NodeJS wrapper that spawns your Haskell executable
● Hooks up pipes for input, output and logging
● At the moment it will spawn a new exe on each invocation
● Future plan: keep the exe running so that it can handle multiple invocations

5. Haskell library
lambdaMain ::
(Aeson.FromJSON event, Aeson.ToJSON res)
=> (event -> IO res) -- ^ Function to process the event
-> IO ()

6. Event types
Types for dealing with common Lambda events
So far
● SNS
● S3
● Kinesis
● APIGateway
Plan to add more.

7. Alternative events
● Compose handlers for different types of events

8. Embedded events
● Some event types (e.g. SNS, APIGateway) have stringified JSON or Base64
embedded within string values in the JSON
● TextValue and Embedded

9. Examples

10. Conclusion
● We have several Lambdas at SEEK using this
● GitHub https://github.com/seek-oss/serverless-haskell
● Also on npm, hackage and stackage
● Future extensions:
○ Allow more than one Lambda invocation
○ Allow multiple functions per project
○ Expand the supported event types
● We would love to get more users
● Pull requests invited