Building the REST API¶

The code is from https://github.com/serverless/examples

We are going to download that repository and do the following things:

➜  06-aws-node-rest-api-with-dynamodb git:(master) ✗ npm i
npm WARN deprecated uuid@2.0.3: Please upgrade  to version 7 or higher.  Older versions may use Math.random() in certain circumstances, which is known to be problematic.  See https://v8.dev/blog/math-random for details.

added 1 package, and audited 2 packages in 610ms

found 0 vulnerabilities

We can examine the serverless.yml file and see that there are some interesting things there, like:

    DYNAMODB_TABLE: ${self:service}-${opt:stage, self:provider.stage}

The table name will be the same as the service name defined at the root, with a suffix of it's stage.

The stage comes from option that are specified either when deploying sls or it will use the provider stage which is dev by default.

Also, the IAM roles are specifying only the permissions we need on one specific table.

  iamRoleStatements:
    - Effect: Allow
      Action:
        - dynamodb:Query
        - dynamodb:Scan
        - dynamodb:GetItem
        - dynamodb:PutItem
        - dynamodb:UpdateItem
        - dynamodb:DeleteItem
      Resource: "arn:aws:dynamodb:${opt:region, self:provider.region}:*:table/${self:provider.environment.DYNAMODB_TABLE}"

The functions are defined like this:

  get:
    handler: todos/get.get
    events:
      - http:
          path: todos/{id}
          method: get
          cors: true

The handler in this case is located at the todos/get.js, it has a method get.

The event is coming from API Gateway, with a path of todo/{id}, method GET.

The CORS variable specifies if the endpoint can be called from other domains.

Finally, at the end of the file we can see the Resources which basically is a CloudFormation template.

resources:
  Resources:
    TodosDynamoDbTable:
      Type: 'AWS::DynamoDB::Table'
      DeletionPolicy: Retain
      Properties:
        AttributeDefinitions:
          -
            AttributeName: id
            AttributeType: S
        KeySchema:
          -
            AttributeName: id
            KeyType: HASH
        ProvisionedThroughput:
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: ${self:provider.environment.DYNAMODB_TABLE}

It lists resources we need to create. In this case we create a TodosDynamoDbTable table.