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https://github.com/seek-oss/serverless-haskell

Deploying Haskell applications to AWS Lambda with Serverless
https://github.com/seek-oss/serverless-haskell

aws aws-lambda haskell haskell-stack serverless

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Deploying Haskell applications to AWS Lambda with Serverless

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README 

        
# Serverless Haskell



![Build status](https://github.com/seek-oss/serverless-haskell/workflows/Build/badge.svg)

[![Hackage](https://img.shields.io/hackage/v/serverless-haskell.svg)](https://hackage.haskell.org/package/serverless-haskell)

[![Stackage LTS](https://www.stackage.org/package/serverless-haskell/badge/lts)](https://www.stackage.org/lts/package/serverless-haskell)

[![Hackage dependencies](https://img.shields.io/hackage-deps/v/serverless-haskell.svg)](https://packdeps.haskellers.com/feed?needle=serverless-haskell)

[![npm](https://img.shields.io/npm/v/serverless-haskell.svg)](https://www.npmjs.com/package/serverless-haskell)



Deploying Haskell code onto [AWS Lambda] as native runtime using [Serverless].



## Prerequisites



* AWS account

* [Stack]

* [NPM]

* [Docker]



## Usage



There are two ways to start, either via the stack template, or directly modifying a project. You may want to use the manual approach as the template specifies a specific stack resolver as it needs to hardcode the `stack.yaml` file.



In either case, you will want to have [Serverless] installed, eg. `npm install -g serverless`.



### Using the stack template



* Create a [Stack] package for your code:



  ```shell

  stack new mypackage https://raw.githubusercontent.com/seek-oss/serverless-haskell/master/serverless-haskell.hsfiles

  ```



* Update the resolver in the `stack.yaml` file. This is hardcoded as the resolver number is not known at template interpolation time. You should pick either the latest resolver, or one you have used before and have thus prebuilt many of the core packages for.



* Install the dependencies and build the project:



  ```shell

  cd mypackage

  npm install

  stack build

  sls invoke local -f mypackage-func

  ```



  This should invoke serverless locally and display output once everything has built.



### Manually



* Create a [Stack] package for your code:



  ```shell

  stack new mypackage

  ```



  LTS 10-17 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:



  ```shell

  cd mypackage

  npm init -y

  npm install --save serverless [email protected]

  ```



  The version of the NPM package to install must match the version of the

  Haskell package.



* Create `serverless.yml` with the following contents:



  ```yaml

  service: myservice



  provider:

    name: aws

    runtime: haskell



  functions:

    myfunc:

      handler: mypackage.mypackage-exe

      # Here, mypackage is the Haskell package name and mypackage-exe is the

      # executable name as defined in the Cabal file. The handler field may be

      # prefixed with a path of the form `dir1/.../dirn`, relative to

      # `serverless.yml`, which points to the location where the Haskell

      # package `mypackage` is defined. This prefix is not needed when the

      # Stack project is defined at the same level as `serverless.yml`.



  plugins:

    - serverless-haskell

  ```



* Write your `main` function:



  ```haskell

  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]

  ```



* Add `aeson` and `serverless-haskell` to `package.yaml`:



  ```yaml

  dependencies:

  - base >= 4.7 && < 5

  - aeson

  - serverless-haskell

  ```



* Build and test locally using `sls invoke local`:



  The `serverless-haskell` plugin will build the package using Stack. Note that

  the first build can take a long time. Consider adding `export SLS_DEBUG=*` so

  you can see what is happening.



  ```

  export SLS_DEBUG=*

  sls invoke local -f myfunc

  ```



* Use `sls deploy` to deploy the executable to AWS Lambda.



  The `serverless-haskell` plugin will build the package using Stack, then upload

  it to AWS together with a JavaScript wrapper to pass the input and output

  from/to AWS Lambda.



  ```

  export SLS_DEBUG=*

  sls deploy

  ```

  You can test the function and see the invocation results with:



  ```

  sls invoke -f myfunc`

  ```



### API Gateway



This plugin supports handling API Gateway requests. Declare the HTTP events

normally in `serverless.yml` and use

[AWSLambda.Events.APIGateway](https://hackage.haskell.org/package/serverless-haskell/docs/AWSLambda-Events-APIGateway.html)

in the handler to process them.



[Serverless Offline] can be used for local testing of API Gateway requests. You

must use `--useDocker` flag so that the native Haskell runtime works correctly.



When using [Serverless Offline], make sure that the project directory is

world-readable, otherwise the started Docker container will be unable to access

the handlers and all invocations will return HTTP status 502.



### Notes



* Only AWS Lambda is supported at the moment. Other cloud providers would

  require different JavaScript wrappers to be implemented.



See

[AWSLambda](https://hackage.haskell.org/package/serverless-haskell/docs/AWSLambda.html)

for documentation, including additional options to control the deployment.



## Development



`master` branch is the stable version. It is normally released to Hackage once

new changes are merged via Git tags.



The package is also maintained in Stackage LTS, provided the dependencies are

not blocking it.



### Testing



* Haskell code is tested with Stack: `stack test`.

* TypeScript code is linted with `eslint`.



### Integration tests



Integration test verifies that the project can build and deploy a complete

function to AWS, and it runs with expected functionality.



Integration test is only automatically run up to deployment due to the need for

an AWS account. To run manually:



* Ensure you have the required dependencies:

  - `curl`

  - [jq]

  - [NPM]

  - [`pkg-config`](pkg-config)

  - `pwgen`

  - [Stack]

* Get an AWS account and add the access credentials into your shell environment.

* Run `./integration-test/run.sh`. The exit code indicates success.

* To verify just the packaging, without deployment, run

  `./integration-test/run.sh --dry-run`.

* By default, the integration test is run with the LTS specified in

  `stack.yaml`. To specify a different series, use `RESOLVER_SERIES=lts-9`.

* To avoid creating a temporary directory for every run, specify

  `--no-clean-dir`. This can speed up repeated test runs, but does not guarantee

  the same results as a clean test.



### Releasing



* Ensure you are on the `master` branch.

* Ensure that all the changes are reflected in the changelog.

* Run the integration tests.

* Run `./bumpversion major|minor|patch`. This will increment the version number,

  update the changelog, create and push the Git tag and the branch.

* If you have released an LTS version, merge the version branch into `master`,

  taking care of the conflicts around version numbers and changelog, and release

  the latest version as well.



[AWS Lambda]: https://aws.amazon.com/lambda/

[Docker]: https://www.docker.com/

[jq]: https://stedolan.github.io/jq/

[NPM]: https://www.npmjs.com/

[pkg-config]: https://www.freedesktop.org/wiki/Software/pkg-config/

[Serverless]: https://serverless.com/framework/

[Serverless Offline]: https://github.com/dherault/serverless-offline

[Stack]: https://haskellstack.org