template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  My Image App - Label images

# This is the global definitions
# In this example the definitions is only for the Lambdas
Globals:
  Function:
    Runtime: python3.6
    Timeout: 600
    MemorySize: 1024

Resources:
  # This is the bucket to upload the images
  ImageBucket:
    Type: AWS::S3::Bucket
    Properties:  # This is done to avoid circular dependencies
      BucketName: !Sub "image-bucket-${AWS::AccountId}"

  # This is the table to save the image tags
  ImageTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: AppImageTable
      BillingMode: PAY_PER_REQUEST
      KeySchema:  # These are the two fields that consists the Primary Key
        - AttributeName: "image-id"
          KeyType: "HASH"  # This is the Partition Key
        - AttributeName: "tag"
          KeyType: "RANGE"  # This is the sort key
      AttributeDefinitions:  # For each reference in the KeySchema we have to set the types
        - AttributeName: "image-id"
          AttributeType: "S"
        - AttributeName: "tag"
          AttributeType: "S"

  # This is the function that send the image to Amazon Rekognition
  # in order to get the tags. It will be triggered when an image is uploaded to the bucket
  RecognizeImageFunction:
    Type: "AWS::Serverless::Function"
    Properties:
      CodeUri: src
      Handler: recognize_image.lambda_handler
      Environment:
        Variables:
          DYNAMODB_TABLE: !Ref ImageTable  # This will be passed as an environ variable to Lambda
      Policies:
        - S3CrudPolicy:  # With this policy the Lambda has read-write access to the bucket
            BucketName: !Sub "image-bucket-${AWS::AccountId}/*"
        - DynamoDBCrudPolicy:  # With this policy the Lambda can red-write to the Table
            TableName: !Ref ImageTable
        - AmazonRekognitionReadOnlyAccess
      Events:  # These are the events that trigger this Lambda Function
        GenerateTags:  # When an object is created in this bucket the Lambda will be triggered for execution
          Type: S3
          Properties:
            Bucket: !Ref ImageBucket
            Events: s3:ObjectCreated:*

Outputs:
  ImageBucket:
    Description: "The bucket to save the images"
    Value: !Ref ImageBucket
  ImageTable:
    Description: "The DynamoDB table to save the images"
    Value: !GetAtt ImageTable.Arn
  RecognizeImageFunction:
    Description: "Lambda to tag the image and save to DynamoDB"
    Value: !GetAtt RecognizeImageFunction.Arn