Upload a file to S3 to trigger a lambda function

This example shows how to upload a file to S3 using a HTML form, and have S3 trigger a lambda function.

Use-cases

Postprocess files uploaded to an S3 bucket.

Setup

Edit serverless.yml and choose a unique S3 bucket name.
Edit generate-form.js and fill in your aws_access_key_id, aws_secret_access_key and bucket_name.
Run yarn install to install crypto-js dependency for generate-form.js.
Generate the HTML form:

yarn install
node generate-form.js

Deploy

In order to deploy the example, simply run:

serverless deploy

The output should look similar to:

Serverless: Creating Stack...
Serverless: Checking Stack create progress...
.....
Serverless: Stack create finished...
Serverless: Packaging service...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading service .zip file to S3 (3.85 MB)...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
........................
Serverless: Stack update finished...
Service Information
service: upload-to-s3-and-postprocess
stage: dev
region: us-east-1
api keys:
  None
endpoints:
  None
functions:
  upload-to-s3-and-postprocess-dev-postprocess

Usage

Open the generated frontend/index.html in your browser, or run:

xdg-open frontend/index.html

Select a PNG image smaller than 1Mb, and click "Upload File to S3".

You should get an XML response similar to:

<PostResponse>
  <Location>https://serverless-fetch-file-and-store-in-s3.s3.amazonaws.com/uploads%2Fimage.png</Location>
  <Bucket>serverless-fetch-file-and-store-in-s3</Bucket>
  <Key>uploads/image.png</Key>
  <ETag>"08c03c6a24e5058b9f3556981a23b1d7"</ETag>
</PostResponse>

After a while, the postprocess function gets triggered by an S3 event:

serverless logs --function postprocess

START RequestId: e2deccf2a0-11e6-b6e3fbcfad7d8c Version: $LATEST
2014 12:32:30.350 (+02:00)	e2deccf2a0-11e6-b6e3fbcfad7d8c	New .png object has been created: uploads/image.png (23975 bytes)
END RequestId: e2deccf2a0-11e6-b6e3fbcfad7d8c
REPORT RequestId: e2deccf2a0-11e6-b6e3fbcfad7d8c	Duration: 2.84 ms	Billed Duration: 100 msMemory Size: 1024 MB	Max Memory Used: 29 MB