70: Haskell Serverless

After we've spent a comical amount of time getting a Linux environment setup it's time to actually try to get Haskell running on aws lambda.

Finally Ready to Go

We’ve got our environment all set up so let’s get going!

Steps

A new stack project using the template stack new my-haskell-lambda https://github.com/theam/aws-lambda-haskell-runtime/raw/master/stack-template.hsfiles --resolver=lts-12.13 --omit-packages Say it with me “stack is not like NPM, it is NOT a package manager” stack handles the management of your tool-chain. resolver ?

Specifies which snapshot is to be used for this project. A snapshot defines a GHC version, a number of packages available for installation, and various settings like build flags. It is called a resolver since a snapshot states how dependencies are resolved. There are currently four resolver types:

omit-packages ? this leaves the extra-depsflag commented out in the stack.yml Added to stack.yml packages: - . extra-deps: - aws-lambda-haskell-runtime-1.0.9 initially I had only added the extra-deps. I didn’t realize that having added --omit-packages I still needed to add packages . running make and we’re off to the races Progress 0/111 aws lambda create-function --function-name lambda-haskell \ --zip-file fileb://build/function.zip --handler src/Lib.handler \ --layers arn:aws:lambda:us-west-2:785355572843:layer:haskell-runtime:2 \ --runtime provided --role arn:aws:iam::XXXXXXXXXX:role/lambda-haskell-role Oh man. needed Success it’s been deployed. Let’s see if it works on the first try… NOPE execute failure. :cry: Oh well, we spelled the handler wrong. AND we had the wrong ‘Layer ARN’ This is the custom runtime, once we updated it to match the read me file, we had :rocket: Lift Off!!

Can we update the code ?

aws lambda update-function-code --zip-file fileb://build/function.zip --publish --function-name lambda-haskell

HELL YES we can.

OK. So what did we actually deploy ? Let’s walk through the code.

Lib source file with aws runtime for having access to the ‘Context’ that is passed in to our application when it’s instantiated.

GHC.Generics for work with JSON

Aeson for (de)serializing JSON to our types

Handler

This is defined in scr/Lib Must be called handler limit of Haskell runtime handler :: Person -> Context -> IO (Either String Person)

Main

import aws runtime again import fully qualified Lib call configureLambda which will dynamically generate our dispatchers for us. also of note, with compared to C++ and Rust runtimes, Haskell doesn’t need the entire runtime included with it. I am guessing it can make smart decisions about what is required we can create more ‘handlers’ just need to remember to import them BOOM

Person API *update age to a negative value or 0 and see the string response. Thanks great!

{ "personAge": 43, "personName": "John Doe" } Picks Resources

AWS Custom Runtimes

Runtime Details with Haskell Medium Post

Custom Haskell Runtime Repo

Lexi Lambda Guide to Haskell 2018

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Jesse Tomchak

Twitter: [@jtomchak](https://Twitter.com/jtomchak)