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s3-object-response

This middleware is a Proof of Concept and requires real world testing before use, not recommended for production

Fetches S3 object as a stream and writes back to s3 object response.

Install​

To install this middleware you can use NPM:

npm install --save @middy/s3-object-response
npm install --save-dev @aws-sdk/client-s3

Options​

  • bodyType (string) (required): How to pass in the s3 object through the handler. Can be stream or promise.
  • AwsClient (object) (default S3Client): S3Client class constructor (i.e. that has been instrumented with AWS XRay). Must be from @aws-sdk/client-s3.
  • awsClientOptions (object) (optional): Options to pass to S3Client class constructor.
  • awsClientCapture (function) (optional): Enable XRay by passing captureAWSv3Client from aws-xray-sdk in.
  • httpsCapture (function) (optional): Enable XRay by passing captureHTTPsGlobal from aws-xray-sdk in.
  • disablePrefetch (boolean) (default false): On cold start requests will trigger early if they can. Setting awsClientAssumeRole disables prefetch.

NOTES:

  • The response from the handler must match the allowed parameters for S3.writeGetObjectResponse, excluding RequestRoute and RequestToken.
  • Lambda is required to have IAM permission for s3-object-lambda:WriteGetObjectResponse

Sample usage​

Stream​

import zlib from 'zlib'
import middy from '@middy/core'
import s3ObjectResponse from '@middy/s3-object-response'

const handler = middy((event, context) => {
  const readStream = context.s3Object
  const transformStream = zlib.createBrotliCompress()
  return {
    Body: readStream.pipe(transformStream)
  }
})

handler.use(
  s3ObjectResponse({
    bodyType: 'stream'
  })
)

Promise​

import zlib from 'zlib'
import middy from '@middy/core'
import s3ObjectResponse from '@middy/s3-object-response'

const handler = middy(async (event, context) => {
  let body = await context.s3Object
  // change body
  return {
    Body: JSON.stringify(body)
  }
})

handler.use(
  s3ObjectResponse({
    bodyType: 'promise'
  })
)

Bundling​

To exclude @aws-sdk add @aws-sdk/client-s3 to the exclude list.