# 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`. - Generate the HTML form: ```bash node generate-form.js ``` ## Deploy In order to deploy the example, simply run: ```bash serverless deploy ``` The output should look similar to: ```bash 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: ```bash 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: ```xml https://serverless-fetch-file-and-store-in-s3.s3.amazonaws.com/uploads%2Fimage.png serverless-fetch-file-and-store-in-s3 uploads/image.png "08c03c6a24e5058b9f3556981a23b1d7" ``` After a while, the postprocess function gets triggerd by an S3 event: ```bash serverless logs --function postprocess ``` ``` START RequestId: e2decc94-f2a0-11e6-b641-e3fbcfad7d8c Version: $LATEST 2017-02-14 12:32:30.350 (+02:00) e2decc94-f2a0-11e6-b641-e3fbcfad7d8c New .png object has been created: uploads/image.png (23975 bytes) END RequestId: e2decc94-f2a0-11e6-b641-e3fbcfad7d8c REPORT RequestId: e2decc94-f2a0-11e6-b641-e3fbcfad7d8c Duration: 2.84 ms Billed Duration: 100 msMemory Size: 1024 MB Max Memory Used: 29 MB ```