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API

We've added an API, using API Gateway so we can handle web requests. These endpoints are defined in the serverless.yml file, and specify the URL path, method, and handler to invoke.

GET /upload_url

Get a presigned key URL that we can use to PUT the file to do an upload.

Ideally we would like a web page that presents an upload form. It would first GET a presigned URL from the API, then the browser would directly PUT the file to that URL. This prevents tying up the API server with potentially long and large upload files.

Until we have a web page and Angular code to handle the form, response and upload, we'll use curl.

First, find the API endpoint based on your stage:

\../node_modules/.bin/sls info --stage shentonfreude

I then set a variable for the URL to make it easy to refer to:

urlget="https://WHATEVER.execute-api.us-east-1.amazonaws.com/shentonfreude/upload_url"

Get a presigned URL from the API, specifying the name of your file as a querystring param:

curl $urlget?filename=ALEX.JPG

{"url": "https://uploads-info-shentonfreude.s3.amazonaws.com/ALEX.JPG?AWSAccessKeyId=..."}

Set a variable to that long URL for convenience:

url="https://uploads-info-shentonfreude.s3.amazonaws.com/ALEX.JPG?AWSAccessKeyId=..."

Then PUT a file to that URL:

curl -i --upload-file ~/Pictures/alex.jpg $url

serverless.yml

We define the function and handler together:

getUploadPSK:
handler: handler.get_upload_url
events:
  - http: GET /upload_url

The Lambda must be given permissions for the presigned URL to allow the upload:

iamRoleStatements:
  - Effect: Allow
    Resource: arn:aws:s3:::uploads-info-${self:provider.stage}/*
    Action:
      - s3:PutObject
      - s3:PutObjectAcl
      - s3:PutObjectTagging

GET /assets

Return info about the assets from the DynamoDB table, as JSON or if 'text/html' is in the request's Accept header, as HTML.

It's naive and just does a table scan, which is expensive and stupid but will be OK for this toy demo (unless we get a lot of items).

I had to fight with DynamoDB to turn numerics returned by boto3 as decimal.Decimal types into plain old int so JSON could render them.

serverless.yml

The endpoint is specified in serverless.yml and we don't have any new permissions to add:

getAssets:                    # JSON, or HTML if "Accepts: text/html"
  handler: handler.get_assets
  events:
    - http:  GET /assets