Dapr牵手.NET学习笔记：状态管理进阶

Posted 2021-10-24 dotNET跨平台

为了防止并发对数据修改造成差异，dapr使用了etag标签来作为版本号，对数据修改进行验证。

下面是对etag的一个demo

appsettings.json中的url配置

"StateUrl": "http://localhost:3500/v1.0/state/statestore"

在PaymentSystem项目中添加两个action

[HttpPost("/writekeyswithetag")]
    public async Task<IActionResult> WriteKeysWithEtag([FromBody] KeyEntityWithEtag[] keys)
    {
        var client = _clientFactory.CreateClient();
        var jsonContent = System.Text.Json.JsonSerializer.Serialize(keys);
        var content = new StringContent(jsonContent);
        var response = await client.PostAsync(_stateUrl, content);
        return Ok(await response.Content.ReadAsStringAsync());
    }


    [HttpGet("/readekeywithetag/{key}")]
    public async Task<IActionResult> ReadKeyWithEtag(string key)
    {
        var client = _clientFactory.CreateClient();
        var response = await client.GetAsync($"{_stateUrl}/{key}");      
        var dataString = await response.Content.ReadAsStringAsync();
        var data = (string.IsNullOrEmpty(dataString) ? null : System.Text.Json.JsonSerializer.Deserialize<OrderPayment>(dataString));
        return new JsonResult(new { result = true, data = new { data = data, etag = response.Headers.SingleOrDefault(s => s.Key.ToLower() == "etag") }, host = Dns.GetHostName() });
    }

实体类

public class OrderPayment
{
    public string PayOrder { get; set; }
    public decimal PayTotal { get; set; }
    public string PayType { get; set; }
    public DateTime PayTime { get; set; }
}
public class KeyEntityWithEtag
{
    public string Key { get; set; }
    public OrderPayment Value { get; set; }
    public string Etag { get; set; }
}

docker-compose.yml

version: '3.4'


services:
  #┌─────────────────────────┐
  #│ Dapr placement1 service │
  #└─────────────────────────┘  
  placement:
    image: "daprio/dapr"
    command: ["./placement", "-port", "50006"]
    ports:
      - "50006:50006"
    networks:
      - b2c-dapr


  #┌────────────────────┐
  #│ Redis1 state store │
  #└────────────────────┘  
  redis:
    image: "redis:latest"
    ports:
      - "6380:6379"
    networks:
      - b2c-dapr
  
  #┌───────────────────────────────────┐
  #│ paymentsystem1 app + Dapr sidecar │
  #└───────────────────────────────────┘  
  paymentsystem1:
    image: ${DOCKER_REGISTRY-}paymentsystem
    depends_on:
      - redis
      - placement
    build:
      context: ../
      dockerfile: /PaymentSystem/Dockerfile
    ports:
      - "3601:3500"
    volumes:   
      - ../PaymentSystem:/PaymentSystem      
    networks:
      - b2c-dapr      
  paymentsystem1-dapr:
     image: "daprio/daprd:latest"
     command: [ "./daprd", "-app-id", "pay", "-app-port", "80","-placement-host-address", "placement:50006","-components-path","/components" ]
     build:
       context: ../
     depends_on:
       - paymentsystem1
     network_mode: "service:paymentsystem1"
     volumes:   
      - ../components:/components 


  #┌───────────────────────────────────┐
  #│ paymentsystem2 app + Dapr sidecar │
  #└───────────────────────────────────┘   
  paymentsystem2:
    image: ${DOCKER_REGISTRY-}paymentsystem
    depends_on:
      - redis
      - placement 
    build:
      context: ../
      dockerfile: /PaymentSystem/Dockerfile
    volumes:   
      - ../PaymentSystem:/PaymentSystem            
    ports:
      - "3602:3500"
    networks:
      - b2c-dapr      
  paymentsystem2-dapr:
     image: "daprio/daprd:latest"
     command: [ "./daprd", "-app-id", "pay", "-app-port", "80" ,"-placement-host-address", "placement:50006","-components-path","/components"]
     build:
       context: ../
     depends_on:
       - paymentsystem2
     network_mode: "service:paymentsystem2"
     volumes:   
      - ../components:/components 
networks:
  b2c-dapr:

提交带有etag标签的数据，多提交几次，可以把etag顶起来

查看etag为非1

这时再次提交就会报错，如果另外的服务更新了这个值，本次提交就会失败，需要再次查询后更新，或作别的业务逻辑处理。