AWS.Lambda.Runtime

These are runtimes designed for AWS Lambda, which accept a handler and return an application that will retreive and execute events as long as a container continues to exist.

Many of these runtimes use AWS.Lambda.Combinators under the hood. For those interested in peeking below the abstractions provided here, please refer to that module.

Documentation

pureRuntime :: (FromJSON event, ToJSON result) => (event -> result) -> IO ()

For pure functions that can never fail.

Use this for simple handlers that just translate input to output without side-effects.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Runtime (pureRuntime)
import Data.Aeson (FromJSON)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: Named -> String
myHandler Named { name } = "Hello, " ++ name ++ "!"

main :: IO ()
main = pureRuntime myHandler

pureRuntimeWithContext :: (FromJSON event, ToJSON result) => (LambdaContext -> event -> result) -> IO ()

For pure functions that can never fail that also need access to the context.

Use this for simple handlers that just translate input to output without side-effects, but that need the AWS Lambda Context as input.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Context (LambdaContext(..))
import AWS.Lambda.Runtime (pureRuntimeWithContext)
import Data.Aeson (FromJSON)
import Data.Text (unpack)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: LambdaContext -> Named -> String
myHandler (LambdaContext { functionName }) (Named { name }) =
  "Hello, " ++ name ++ " from " ++ unpack functionName ++ "!"

main :: IO ()
main = pureRuntimeWithContext myHandler

fallibleRuntime :: (FromJSON event, ToJSON result) => (event -> Either String result) -> IO ()

For pure functions that can still fail.

Use this for simple handlers that just translate input to output without side-effects, but can fail.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Runtime (fallibleRuntime)
import Data.Aeson (FromJSON)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: Named -> Either String String
myHandler (Named { name }) =
  if name == "World" then
    Right "Hello, World!"
  else
    Left "Can only greet the world."

main :: IO ()
main = fallibleRuntime myHandler

fallibleRuntimeWithContext :: (FromJSON event, ToJSON result) => (LambdaContext -> event -> Either String result) -> IO ()

For pure functions that can still fail.

Use this for simple handlers that just translate input to output without side-effects, but can fail and need the AWS Lambda Context as input.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Context (LambdaContext(..))
import AWS.Lambda.Runtime (fallibleRuntimeWithContext)
import Data.Aeson (FromJSON)
import Data.Text (unpack)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: LambdaContext -> Named -> Either String String
myHandler (LambdaContext { functionName }) (Named { name }) =
  if name == "World" then
    Right $ "Hello, World from " ++ unpack functionName ++ "!"
  else
    Left "Can only greet the world."

main :: IO ()
main = fallibleRuntimeWithContext myHandler

ioRuntime :: (FromJSON event, ToJSON result) => (event -> IO (Either String result)) -> IO ()

For functions with IO that can fail in a pure way (or via throw).

Use this for handlers that need any form of side-effect such as reading environment variables or making network requests. However, do not use this runtime if you need stateful (caching) behaviors.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Runtime (ioRuntime)
import Data.Aeson (FromJSON)
import System.Environment (getEnv)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: Named -> IO (Either String String)
myHandler (Named { name }) = do
  greeting <- getEnv "GREETING"
  return $ pure $ greeting ++ name

main :: IO ()
main = ioRuntime myHandler

ioRuntimeWithContext :: (FromJSON event, ToJSON result) => (LambdaContext -> event -> IO (Either String result)) -> IO ()

For functions with IO that can fail in a pure way (or via throw).

Use this for handlers that need any form of side-effect such as reading environment variables or making network requests, and also need the AWS Lambda Context as input. However, do not use this runtime if you need stateful (caching) behaviors.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Context (LambdaContext(..))
import AWS.Lambda.Runtime (ioRuntimeWithContext)
import Data.Aeson (FromJSON)
import Data.Text (unpack)
import System.Environment (getEnv)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: LambdaContext -> Named -> IO (Either String String)
myHandler (LambdaContext { functionName }) (Named { name }) = do
  greeting <- getEnv "GREETING"
  return $ pure $ greeting ++ name ++ " from " ++ unpack functionName ++ "!"

main :: IO ()
main = ioRuntimeWithContext myHandler

readerTRuntime :: (FromJSON event, ToJSON result) => (event -> ReaderT LambdaContext IO result) -> IO ()

For functions that can read the lambda context and use IO within the same monad.

Use this for handlers that need any form of side-effect such as reading environment variables or making network requests, and prefer to access the AWS Lambda Context in the same monad. However, do not use this runtime if you need stateful (caching) behaviors.

{-# LANGUAGE NamedFieldPuns, DeriveGeneric #-}

module Main where

import AWS.Lambda.Context (LambdaContext(..))
import AWS.Lambda.Runtime (readerTRuntime)
import Control.Monad.Reader (ReaderT, ask)
import Control.Monad.Trans (liftIO)
import Data.Aeson (FromJSON)
import Data.Text (unpack)
import System.Environment (getEnv)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: Named -> ReaderT LambdaContext IO String
myHandler Named { name } = do
  LambdaContext { functionName } <- ask
  greeting <- liftIO $ getEnv "GREETING"
  return $ greeting ++ name ++ " from " ++ unpack functionName ++ "!"

main :: IO ()
main = readerTRuntime myHandler

mRuntime :: (MonadCatch m, MonadIO m, FromJSON event, ToJSON result) => (event -> m result) -> m ()

For any monad that supports IO and catch. Useful if you need caching behaviours or are comfortable manipulating monad transformers, want full control over your monadic interface, but don't need to inspect the LambdaContext.

{-# LANGUAGE DeriveGeneric, NamedFieldPuns #-}

module Main where

import AWS.Lambda.Runtime (mRuntime)
import Control.Monad.State.Lazy (StateT, evalStateT, get, put)
import Control.Monad.Trans (liftIO)
import Data.Aeson (FromJSON)
import System.Environment (getEnv)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: Named -> StateT Int IO String
myHandler Named { name } = do
  greeting <- liftIO $ getEnv "GREETING"

  greetingCount <- get
  put $ greetingCount + 1

  return $ greeting ++ name ++ " (" ++ show greetingCount ++ ")!"

main :: IO ()
main = evalStateT (mRuntime myHandler) 0

mRuntimeWithContext :: (MonadCatch m, MonadIO m, FromJSON event, ToJSON result) => (LambdaContext -> event -> m result) -> m ()

For any monad that supports IO and catch. Useful if you need caching behaviours or are comfortable manipulating monad transformers, and want full control over your monadic interface.

{-# LANGUAGE DeriveGeneric, NamedFieldPuns #-}

module Main where

import AWS.Lambda.Context (LambdaContext(..))
import AWS.Lambda.Runtime (mRuntimeWithContext)
import Control.Monad.State.Lazy (StateT, evalStateT, get, put)
import Control.Monad.Trans (liftIO)
import Data.Aeson (FromJSON)
import Data.Text (unpack)
import System.Environment (getEnv)
import GHC.Generics (Generic)

data Named = Named {
  name :: String
} deriving Generic
instance FromJSON Named

myHandler :: LambdaContext -> Named -> StateT Int IO String
myHandler LambdaContext { functionName } Named { name } = do
  greeting <- liftIO $ getEnv "GREETING"

  greetingCount <- get
  put $ greetingCount + 1

  return $ greeting ++ name ++ " (" ++ show greetingCount ++ ") from " ++ unpack functionName ++ "!"

main :: IO ()
main = evalStateT (mRuntimeWithContext myHandler) 0