aws-serverless-lottery

在本次实验中，我们将会通过AWS Serverless应用构建一个无服务器化的抽奖程序。本次的实验涉及到的服务有：

前提条件

本文实验基于AWS**区宁夏区(cn-northwest-1)作示例。所有控制台链接均直接连接到北京区console。如使用海外区账号，请不要点击此直达连接，在global控制台选择相应产品即可。
如果您使用的是AWS**区账号，账号默认屏蔽了80,8080,443三个端口，需要先申请打开443端口才可以正常使用API Gateway的服务。如果是海外账号，没有此限制。
如何判断自己的账号是**区账号还是海外区账号？请查看自己的控制台链接，console.amazonaws.cn为**区，console.aws.amazon.com为海外区账号。
在Identiy Access Management服务中创建一个本次实验需要用到的AWS Lambda服务角色，包含本次实验需要使用到的服务权限。角色包含如下四个托管的策略
- AmazonDynamoDBFullAccess
- AWSLambdaBasicExecutionRole
- AmazonSNSFullAccess
- AWSStepFunctionsFullAccess

具体的角色创建流程，可以参考如下连接 AWS Lambda Execution Role Creating a Role to Delegate Permissions to an AWS Service

Architecture

Workflow Overview

详细步骤

创建AWS Step Functions 状态机

进入AWS控制台，在服务中搜索Step Functions
进入Step Functions服务后，点击左侧的活动栏，并点击状态机
进入状态机主页面后，选择创建状态机
在定义状态机栏目下，选择默认使用代码段创作。同时在详细信息栏目输入状态机名称Lottery
在状态机定义栏目下，复制如下状态机定义文件，通过Amazon States Language来定义状态机的状态流转

{
  "Comment": "A simple AWS Step Functions state machine that simulates the lottery session",
  "StartAt": "Input Lottery Winners",
  "States": {
    "Input Lottery Winners": {
        "Type": "Task",
        "Resource": "<InputWinners:ARN>",
        "ResultPath": "$",
        "Catch": [ 
            {          
              "ErrorEquals": [ "CustomError" ],
              "Next": "Failed"      
            },
            {          
              "ErrorEquals": [ "States.ALL" ],
              "Next": "Failed"      
            } 
          ],
        "Next": "Random Select Winners"
    }, 
    "Random Select Winners": {
      "Type": "Task",
      "InputPath": "$.body",
      "Resource": "<RandomSelectWinners:ARN>",
      "Catch": [ 
        {          
          "ErrorEquals": [ "States.ALL" ],
          "Next": "Failed"      
        } 
      ],      
     "Retry": [ 
        {
          "ErrorEquals": [ "States.ALL"],          
          "IntervalSeconds": 1, 
          "MaxAttempts": 2
        } 
      ],
      "Next": "Validate Winners"
    },
    "Validate Winners": {
      "Type": "Task",
      "InputPath": "$.body",
      "Resource": "<ValidateWinners:ARN>",
      "Catch": [ 
        {          
          "ErrorEquals": [ "States.ALL" ],
          "Next": "Failed"      
        } 
      ],      
     "Retry": [ 
        {
          "ErrorEquals": [ "States.ALL"],          
          "IntervalSeconds": 1, 
          "MaxAttempts": 2
        } 
      ],
      "Next": "Is Winner In Past Draw"
    },
    "Is Winner In Past Draw": {
      "Type" : "Choice",
        "Choices": [
          {
            "Variable": "$.status",
            "NumericEquals": 0,
            "Next": "Send SNS and Record In Dynamodb"
          },
          {
            "Variable": "$.status",
            "NumericEquals": 1,
            "Next": "Random Select Winners"
          }
      ]
    },
    "Send SNS and Record In Dynamodb": {
      "Type": "Parallel",
      "End": true,
      "Catch": [ 
        {          
          "ErrorEquals": [ "States.ALL" ],
          "Next": "Failed"      
        } 
      ],      
     "Retry": [ 
        {
          "ErrorEquals": [ "States.ALL"],          
          "IntervalSeconds": 1, 
          "MaxAttempts": 2
        } 
      ],
      "Branches": [
        {
         "StartAt": "Notify Winners",
         "States": {
           "Notify Winners": {
             "Type": "Task",
             "Resource": "arn:aws-cn:states:::sns:publish",
             "Parameters": {
               "TopicArn": "<Notification:ARN>",
               "Message.$": "$.sns"
             },
             "End": true
           }
         }
       },
       {
         "StartAt": "Record Winner Queue",
         "States": {
           "Record Winner Queue": {
             "Type": "Task",
             "InputPath": "$.body",
             "Resource":
               "<RecordWinners:ARN>",
             "TimeoutSeconds": 300,
             "End": true
           }
         }
       }
      ]
    },
    "Failed": {
        "Type": "Fail"
     }
  }
}

在状态机定义栏目的右侧，点击刷新按钮，可以看到状态机流转的流程图。点击下一步
在配置设置下，选择为我创建IAM角色, 输入自定义的IAM角色名称MyStepFunctionsExecutionRole
点击创建状态机完成创建过程

创建AWS Lambda任务

为了实现Step Functions状态机流转下的任务，我们这次实现会用到AWS Lambda作为我们业务的实现环境

进入AWS控制台，选择服务然后输入Lambda进入AWS Lambda控制台
选择创建函数，然后选择从头开始创作来自定义我们的实验程序
首先我们需要创建状态机中的第一个状态任务Input Lottery Winners，输入函数名称Lottery-InputWinners来定义幸运儿的数量。运行语言选择Python 3.7。同时需要选择函数执行的权限, 这里我们选择使用现用角色，选择我们在前提条件下创建的IAM角色
点击创建函数
在函数代码栏目下输入如下代码块

import json

class CustomError(Exception):
    pass

def lambda_handler(event, context):
    num_of_winners = event['input']
    
    # Trigger the Failed process
    if 'exception' in event:
        raise CustomError("An error occurred!!")
    
    return {
        "body": {
            "num_of_winners": num_of_winners
        }
    }

点击右上角的保存
保存成功后复制页面右上角的ARN，替换原Step Functions状态机定义下的<InputWinners:ARN>

接下来我们还需要创建另外三个需要定义的状态机业务逻辑，创建过程和上面的Lottery-InputWinners一致，下面是具体的状态机AWS Lambda代码块

Lottery-RandomSelectWinners 代码块

import json
import boto3
from random import randint
from boto3.dynamodb.conditions import Key, Attr

TOTAL_NUM = 10

def lambda_handler(event, context):
    # variables
    num_of_winners = event['num_of_winners']
    
    # query in dynamodb
    dynamodb = boto3.resource('dynamodb', region_name='cn-northwest-1')
    table = dynamodb.Table('Lottery-Employee')

    # random select the winners, if has duplicate value, re-run the process
    while True:
        lottery_serials = [randint(1,TOTAL_NUM) for i in range(num_of_winners)]
        if len(lottery_serials) == len(set(lottery_serials)):
            break
    
    # retrieve the employee details from dynamodb
    results = [table.query(KeyConditionExpression=Key('lottery_serial').eq(serial), IndexName='lottery_serial-index') for serial in lottery_serials]
    
    # format results
    winner_details = [result['Items'][0] for result in results]
    
    return {
        "body": {
            "num_of_winners": num_of_winners,
            "winner_details": winner_details
        }
    }

保存成功后复制页面右上角的ARN，替换原Step Functions状态机定义下的<RandomSelectWinners:ARN>

Lottery-ValidateWinners代码块

import json
import boto3
from boto3.dynamodb.conditions import Key, Attr

def lambda_handler(event, context):
    # variables
    num_of_winners = event['num_of_winners']
    winner_details = event['winner_details']
    
    # query in dynamodb
    dynamodb = boto3.resource('dynamodb', region_name='cn-northwest-1')
    table = dynamodb.Table('Lottery-Winners')

    # valiate whether the winner has already been selected in the past draw
    winners_employee_id = [winner['employee_id'] for winner in winner_details]
    results = [table.query(KeyConditionExpression=Key('employee_id').eq(employee_id)) for employee_id in winners_employee_id]
    output = [result['Items'] for result in results if result['Count'] > 0]
    
    # if winner is in the past draw, return 0 else return 1
    has_winner_in_queue = 1 if len(output) > 0 else 0
    
    # format the winner details in sns
    winner_names = [winner['employee_name'] for winner in winner_details]
    
    name_s = ""
    for name in winner_names:
        name_s += name
        name_s += " "
        
    return {
        "body": {
            "num_of_winners": num_of_winners,
            "winner_details": winner_details
        },
        "status": has_winner_in_queue,
        "sns": "Congrats! [{}] You have selected as the Lucky Champ!".format(name_s.strip())
    }

保存成功后复制页面右上角的ARN，替换原Step Functions状态机定义下的<ValidateWinners:ARN>

Lottery-RecordWinners 代码块

import json
import boto3
from boto3.dynamodb.conditions import Key, Attr

def lambda_handler(event, context):
    # variables
    winner_details = event['winner_details']
    
    # retrieve the winners' employee id
    employee_ids = [winner['employee_id'] for winner in winner_details]
    
    # save the records in dynamodb
    dynamodb = boto3.resource('dynamodb', region_name='cn-northwest-1')
    table = dynamodb.Table('Lottery-Winners')
    
    for employee_id in employee_ids:
        table.put_item(Item={
            'employee_id': employee_id
        })
        
    return {
        "body": {
            "winners": winner_details
        },
        "status_code": "SUCCESS" 
    }

保存成功后复制页面右上角的ARN，替换原Step Functions状态机定义下的<RecordWinners:ARN>

创建AWS SNS 通知服务

进入AWS控制台，在服务中搜索SNS
在SNS控制面板中，选择主题, 然后选择创建主题
在创建新主题弹框中，输入

主题名称: Lottery-Notification
显示名称: Lottery

创建主题后，会进入主题详细信息页面，这时候我们需要创建订阅来对接我们的消息服务，例如邮件服务（本次实验使用邮件服务来作为消息服务）
点击创建订阅, 在弹框中选择

协议: Email
终端节点: <填入自己的邮箱地址>

点击请求确认, 然后到上面填写的邮箱地址中确认收到信息，表示确认该邮箱可以接收来自AWS SNS该主题的通知消息
复制主题详细页面的主题ARN，替换Step Functions状态机下的<Notification:ARN>

创建Amazon Dynamodb 服务

本次实验需要创建两张Dynamodb表来记录员工信息和幸运儿信息。使用Dynamodb能更快地通过托管的方式记录数据同时免去数据库运维的压力。

进入AWS控制台，在服务中搜索Dynamodb
在左侧控制栏中选在表, 然后在主页面中选择创建表
在创建Dynamodb表中，填入如下信息
- 表名称：Lottery-Winners
- 主键：employee_id
表设置中确认勾选使用默认设置,点击创建
同样的设置步骤，点击创建表,在创建Dynamodb表中，填入如下信息
- 表名称：Lottery-Employee
- 主键：employee_id
表设置中确认勾选使用默认设置,点击创建
等待表创建完成后, 通过本repo中的request-items.json文件导入数据到Lottery-Employee

$ aws dynamodb batch-write-item --request-items file://request-items.json

选择表Lottery-Employee Tab页面中的索引, 点击创建索引
- 主键：lottery_serial, 字段类型选择数字
- 索引名称：lottery_serial-index

执行 Step Functions 状态机

进入AWS控制台，在服务中搜索Step Functions
进入之前创建的状态机Lottery
点击启动执行
在弹框中填入输入的json 文本，这里的input代表在本次实验中需要抽取的获奖人数

{
    "input": 2
}

点击启动执行

实验最终效果

Dynamodb表中Lottery-Winners记录幸运儿
邮件会收取到辛运儿的信息

清除实验资源

删除Dynamodb 创建的表 Lottery-Employee 和 Lottery-Winners
删除状态机 Lottery
删除Lambda函数
删除SNS主题Lottery-Notification

nikosheng/aws-serverless-lottery