@effect-aws/lambda

Clean way to write AWS Lambda handlers using Effect.

It provides a makeLambda function that takes an EffectHandler and returns a native promise Lambda handler function.

The implementation supports defining global runtime layer with graceful shutdown. So all finalizers defined by acquireRelease will be called on lambda downscaling.

Installation

npm install --save @effect-aws/lambda

Usage

Without dependencies:

import { Effect } from "effect"
import { EffectHandler, makeLambda, SNSEvent } from "@effect-aws/lambda"

// Define your effect handler
const myEffectHandler: EffectHandler<SNSEvent, never> = (event, context) => {
  // Your effect logic here
  return Effect.succeed("Hello, World!")
}

// Create the Lambda handler
export const handler = makeLambda(myEffectHandler)

With dependencies:

import { EffectHandler, makeLambda, SNSEvent } from "@effect-aws/lambda"
import * as Logger from "@effect-aws/powertools-logger"
import { Context, Effect, Layer } from "effect"

interface FooService {
  bar: () => Effect.Effect<never, never, void>
}
const FooService = Context.Tag<FooService>()
const FooServiceLive = Layer.succeed(
  FooService,
  FooService.of({ bar: () => Logger.logInfo("Not implemented") })
)

// Define your effect handler with dependencies
const myEffectHandler: EffectHandler<SNSEvent, FooService> = (event, context) =>
  Effect.gen(function* () {
    yield* Logger.logInfo("Received event", { event, context })
    const service = yield* FooService
    return yield* service.bar()
  })

// Create the global layer
const LambdaLive = Layer.provideMerge(
  FooServiceLive,
  Logger.DefaultPowerToolsLoggerLayer
)

// Create the Lambda handler
export const handler = makeLambda(myEffectHandler, LambdaLive)

Streaming:

import { S3 } from "@effect-aws/client-s3"
import { Handler, LambdaHandler } from "@effect-aws/lambda"
import { NodeStream } from "@effect/platform-node"
import { Cause, Effect, Stream } from "effect"
import { Readable } from "node:stream"
import { createGzip } from "node:zlib"

/**
 * Streaming handler that reads a file from S3, compresses it using gzip, and
 * returns the compressed data as a stream.
 */
const streamHandler = () => {
  const stream = S3.getObject({
    Bucket: "example-bucket",
    Key: "file.txt"
  }).pipe(
    Effect.map((result) =>
      NodeStream.fromReadable(
        () => result.Body as Readable,
        (e) => new Cause.UnknownException(e)
      )
    ),
    Stream.unwrap
  )

  return stream.pipe(
    Stream.pipeThroughChannelOrFail(
      NodeStream.fromDuplex(
        () => createGzip(),
        (e) => new Cause.UnknownException(e)
      )
    )
  )
}

export const handler: Handler = LambdaHandler.stream({
  handler: streamHandler,
  layer: S3.defaultLayer
})