Blog-TryDynamoDB

app.py

import os
import json
import boto3
import decimal


def lambda_handler(event, context):
    table = boto3.resource('dynamodb').Table(os.getenv('TABLE_NAME'))

    param = event['pathParameters']['param']

    ret_get_item = table.get_item(
        Key={
            'name': param
        }
    )

    # ret_get_itemに「reference」を含む場合、エイリアスレコードのため、本体情報を取得する
    if 'reference' in ret_get_item['Item']:
        ret_get_item = table.get_item(Key={
          'name': ret_get_item['Item']['reference']
        })

    # 実体レコードのみ全て取得する
    ret_scan = table.scan(
        IndexName=os.getenv('GSI_NAME')
    )

    response = {
        'get_item': ret_get_item['Item'],
        'scan': ret_scan['Items']
    }

    return {
        'statusCode': 200,
        'body': json.dumps(response, cls=DecimalEncoder),
    }


# https://docs.aws.amazon.com/ja_jp/amazondynamodb/latest/developerguide/GettingStarted.Python.03.html
# Helper class to convert a DynamoDB item to JSON.
class DecimalEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, decimal.Decimal):
            if abs(o) % 1 > 0:
                return float(o)
            else:
                return int(o)
        return super(DecimalEncoder, self).default(o)

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Sample SAM Template for TryDynamoDB

Globals:
  Function:
    Timeout: 3

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello_world/
      Handler: app.lambda_handler
      Runtime: python3.6
      Environment:
        Variables:
            TABLE_NAME: !Ref ColorTable
            GSI_NAME: name_ja_gsi
      # https://github.com/awslabs/serverless-application-model/blob/master/docs/policy_templates.rst
      # https://github.com/awslabs/serverless-application-model/blob/develop/samtranslator/policy_templates_data/policy_templates.json
      Policies:
        DynamoDBReadPolicy:
            TableName: !Ref ColorTable
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /color/{param}
            Method: get

  ColorTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: TryDynamoDB-ColorTable
      AttributeDefinitions:
        - AttributeName: name
          AttributeType: S
        - AttributeName: name_ja
          AttributeType: S
      KeySchema:
        - AttributeName: name
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: 1
        WriteCapacityUnits: 1
      GlobalSecondaryIndexes:
        - IndexName: name_ja_gsi
          KeySchema:
            - AttributeName: name_ja
              KeyType: HASH
          Projection:
            ProjectionType: ALL
          ProvisionedThroughput:
            ReadCapacityUnits: 1
            WriteCapacityUnits: 1

Outputs:
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/color/{param}"