无服务器应用程序接口开发 Serverless App development REST API- AWS Lambda + API Gateway + DynamoDB

Author: Zizhun Guo

作者:

写于： 14 May 2020

Author：Zizhun Guo Contact: zg2808@rit.edu Phone: (585)284-0464 Date: May 14th 2020
Technology stack： Serverless AWS S3/Lambda/API Gateway/DynamoDB Node.JS Tools: VSCode/terminal System: Windows/UBuntu

Terms serverless: 朴素的理解：这个serverless类似是一个集成框架，类似提供蓝图功能帮助AWS CloudFormation快速搭建模块，这样可以快速搭建部署不同的服务，比如静态/动态网站，restAPI等等。Serverless Github示例工程。如果单独部署，比如lambda部署function测试，API Gateway部署GET/POST激活特定的lambda function，AWS S3单独传打包好的项目文件去部署，然后链接数据库等等。这个serverless有个ymal的配置文件可以帮助配置整个项目，部署前需要安装AWS CLI在电脑上用来激活IAM的身份验证。专业性理解：按需使用，让开发专注于业务，按内存时间计费，依赖特定云平台及服务(Lambda)。 Image 1: Serverless SPA架构

Lambda 如何看待 AWS Lambda ？ - 知乎 FaaS(Function as a Service)，直接部署function到AWS上，不需要理会任何关于服务器方面的工作，都交给云平台了。

API Gateway

Amazon API Gateway 是一种完全托管的服务，可以帮助开发者轻松创建、发布、维护、监控和保护任意规模的 API。所有API的请求入口。 DaynamoDB Amazon DynamoDB is a fully managed proprietary NoSQL database service that supports key-value and document data structures and is offered by Amazon.com as part of the Amazon Web Services portfolio.

AWS S3

Amazon S3 or Amazon Simple Storage Service is a service offered by Amazon Web Services that provides object storage through a web service interface. 存储桶bucket, 可以存储对象读取写入，类似云盘。

SETUP IAM add user sets programming access sets attach current policy as AdminnistratorAccess gets Access key ID and secret access key bind it to environment so that serverless can use it to access Lambda & API Gateway Image 2: setup Credential for serverless

Serverless Install 两种方法：方法一：用git clone下来实例project，然后cd到目录下操作。方法二：安装命令

serverless install -u https://github.com/serverless/examples/tree/master/aws-node-rest-api-with-dynamodb -n aws-node-rest-api-with-dynamodb

查看配置文件和JS代码

serverless.yml

provider:
  name: aws
  runtime: nodejs10.x
  environment:
    DYNAMODB_TABLE: ${self:service}-${opt:stage, self:provider.stage}
  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}"

functions:
  create:
    handler: todos/create.create
    events:
      - http:
          path: todos
          method: post
          cors: true

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}

get.js

'use strict';

const AWS = require('aws-sdk'); // eslint-disable-line import/no-extraneous-dependencies

const dynamoDb = new AWS.DynamoDB.DocumentClient();

module.exports.get = (event, context, callback) => {
  const params = {
    TableName: process.env.DYNAMODB_TABLE,
    Key: {
      id: event.pathParameters.id,
    },
  };

  // fetch todo from the database
  dynamoDb.get(params, (error, result) => {
    // handle potential errors
    if (error) {
      console.error(error);
      callback(null, {
        statusCode: error.statusCode || 501,
        headers: { 'Content-Type': 'text/plain' },
        body: 'Couldn\'t fetch the todo item.',
      });
      return;
    }

    // create a response
    const response = {
      statusCode: 200,
      body: JSON.stringify(result.Item),
    };
    callback(null, response);
  });
};

query id, 如果有则返回200及内容，没有则返回501异常。

部署Deploy 5.1 安装dependencies
```
npm install
```
5.2 部署
```
serverless deploy
```
Image 3: Deployed serverless

结果及测试利用ubuntu测试指令：

curl -X POST https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos --data '{ "text": "Zizhguo serverless" }'

Image 4: Test POST Create statement 有返回结果，登录AWS DynamoDB验证结果： Image 5: Succesful return the created record

数据有添加，说明添加数据没有问题，其他的REST API分别是：

  (已测试)POST - https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos
  GET - https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos
  GET - https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos/{id}
  PUT - https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos/{id}
  DELETE - https://szye94dpr1.execute-api.us-east-1.amazonaws.com/dev/todos/{id}

Summary More Serverless examples: Github Repo: https://github.com/serverless/examples Image 6: More examples
Reference:

https://www.serverless.com/framework/docs/providers/aws/guide/credentials/

https://serverless.ink/#serverless-%E7%9A%84%E9%97%AE%E9%A2%98

https://zhuanlan.zhihu.com/p/31090697

https://serverless.ink/#%E4%BB%80%E4%B9%88%E6%98%AF-serverless-%E6%9E%B6%E6%9E%84

https://www.serverless.com/framework/docs/providers/aws/guide/credentials/