今日から始めるサーバーレス SAM【API Gateway + Lambda + DynamoDB】

$ sam --version
SAM CLI, version 0.40.0

$ sam init
Which template source would you like to use?
    1 - AWS Quick Start Templates
    2 - Custom Template Location
Choice: 1

Which runtime would you like to use?
    1 - nodejs12.x
    2 - python3.8
    3 - ruby2.5
    4 - go1.x
    5 - java11
    6 - dotnetcore2.1
    7 - nodejs10.x
    8 - python3.7
    9 - python3.6
    10 - python2.7
    11 - java8
    12 - dotnetcore2.0
    13 - dotnetcore1.0
Runtime: 1

Project name [sam-app]: sample

Cloning app templates from https://github.com/awslabs/aws-sam-cli-app-templates.git

-----------------------
Generating application:
-----------------------
Name: sample
Runtime: nodejs12.x
Dependency Manager: npm
Application Template: hello-world
Output Directory: .

Next steps can be found in the README file at ./sample/README.md

.
├── README.md
├── events
│   └── event.json
├── hello-world
│   ├── app.js
│   ├── package.json
│   └── tests
│       └── unit
│           └── test-handler.js
└── template.yaml

$ sam build

$ sam deploy --guided

1. Stack Name // スタック名を入力
2. AWS Region // お好きなAWSリージョン
3. Confirm changes before deploy
  // デプロイ実行前にデプロイによって変更されるスタックの状態を確認した上で、
  // デプロイを実行できるようにするかどうか（yesにしておいて問題ありません）
4. Allow SAM CLI IAM role creation
  // SAM CLIがIAMロールを作っても良いかどうか（yesにしておいて問題ありません）
5. Save arguments to samconfig.toml
  // samconfig.tomlを作成し、
  // その中にデフォルトのデプロイパラメータを書き込んでおくかどうか（yesにしておいて問題ありません）

{"message":"hello world"}

  PostFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: post/
      Handler: app.lambdaHandler
      Runtime: nodejs12.x
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /post
            Method: post
      Role: !GetAtt lambdaFunctionRole.Arn
  PostItems:
    Type: AWS::DynamoDB::Table
    Properties:
      AttributeDefinitions:
        -
          AttributeName: 'partitionKey'
          AttributeType: 'S'
      TableName: 'postItems'
      KeySchema:
        -
          AttributeName: 'partitionKey'
          KeyType: 'HASH'
      ProvisionedThroughput:
        ReadCapacityUnits: 1
        WriteCapacityUnits: 1
  lambdaFunctionRole: # lambda関数がDynamoDBとCloudWatchにアクセスするためのロール
    Type: AWS::IAM::Role
    Properties:
      RoleName: 'RoleForLambdaFunction'
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
        -
          Effect: Allow
          Principal:
            Service:
              - lambda.amazonaws.com
          Action:
          - sts:AssumeRole
      Policies:
        -
          PolicyName: 'FullAccessToDynamoDB'
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
            -
              Effect: Allow
              Action:
                - dynamodb:*
              Resource: "*"
        -
          PolicyName: 'WriteLimitedAccessToCloudWatch'
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
            -
              Effect: Allow
              Action:
                - logs:*
              Resource: "*"

const AWS = require('aws-sdk')
const dynamo = new AWS.DynamoDB.DocumentClient({region: 'us-west-2'})

exports.lambdaHandler = async (event, _, _) => {
  const requestBody = JSON.parse(event.body)

  const table = 'postItems'
  const items = {
    partitionKey: requestBody.partitionKey,
  }
  const params = {
    TableName: table,
    Item: items,
  }

  try {
    await dynamo.put(params, (err, data) => {
      if (err) console.error(err)
    }).promise()

    const response = {
      statusCode: 200,
      body: JSON.stringify(items)
    }
    return response
  } catch(err) {
    console.error(err)
    return err
  }
}

$ sam build

$ sam deploy

Deploy this changeset? [y/N]: y