【EFCore】.NET Core + EFCore 实现数据读写分离

目录

介绍

为什么要读写分离？

如何实现读写分离？

为什么一个主库多个从库？

是否有缺点？

如何解决延迟问题？

具体如何实现？

实现

SqlServer 实现

.NET Core MVC项目实现

Models层实现

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如今，我们操作数据库一般用ORM框架

现在用.NET Core + EFCore + SqlServer 实现数据读写分离

介绍

为什么要读写分离？

降低数据库服务器的压力

 

如何实现读写分离？

1.一个主库多个从库

2.配置主库复制数据到从库

 

 

为什么一个主库多个从库？

一般查询多于增删改，这就是我们常说的二八原则，20%操作是增删改，80%操作是查询

 

是否有缺点？

有延迟

 

如何解决延迟问题？

比较及时性的数据还是通过主库查询

 

具体如何实现？

通过发布服务器，主库发布，而从库订阅，从而实现主从库

实现

SqlServer 实现

使用SqlServer 2019，新建一个主库，创建表，再通过本地发布创建发布，

然后通过本地订阅订阅主库，创建两个从库

.NET Core MVC项目实现

项目结构

首先，在appsettings.json配置数据库连接字符串

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "EFCoreTestToRead": "Server=GREAMBWANG-DC\\MSSQLSERVER2019;Database=EFCoreTestToRead01;Trusted_Connection=True;,Server=GREAMBWANG-DC\\MSSQLSERVER2019;Database=EFCoreTestToRead02;Trusted_Connection=True;",
    "EFCoreTestToWrite": "Server=GREAMBWANG-DC\\MSSQLSERVER2019;Database=EFCoreTest;Trusted_Connection=True;"
  }
}

Models层实现

创建模型

public class UserInfo
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }

}

创建上下文

public class EFCoreContext : DbContext
{
    public EFCoreContext(string connectionString)
    {
        ConnectionString = connectionString;

        //创建数据库
        //Database.EnsureCreated();
    }

    private string ConnectionString { get; }

    public DbSet UserInfo { get; set; }

    /// 

    /// 配置连接数据库
    /// 
    /// 
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        //base.OnConfiguring(optionsBuilder);
        optionsBuilder.UseSqlServer(ConnectionString);

    
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        //base.OnModelCreating(modelBuilder); 
        
        //初始化数据
        modelBuilder.Entity().HasData(new List()
        {
            new UserInfo() { Id = 1, Name = "哈哈", Age = 17 },
            new UserInfo() { Id = 2, Name = "呵呵", Age = 18 },
            new UserInfo() { Id = 3, Name = "嘻嘻", Age = 19 }
        });
    }
}

创建上下文工厂

读写枚举

public enum WriteAndReadEnum
{
    Write,
    Read
} 

接口

public interface IDbContextFactory
{
    EFCoreContext CreateContext(WriteAndReadEnum writeAndRead);
}

实现

在实现数据查询上，可以使用不同的策略，一般有随机策略，权重策略，轮询策略

随机策略：随机选择一个从库进行查询

权重策略：根据权重比例选择从库查询

轮询策略：根据顺序选择从库查询

public class DbContextFactory : IDbContextFactory
{
    private IConfiguration Configuration { get; }
    private string[] ReadConnectionStrings;
    public DbContextFactory(IConfiguration configuration)
    {
        Configuration = configuration;
        ReadConnectionStrings = Configuration.GetConnectionString("EFCoreTestToRead").Split(",");
    }

    public EFCoreContext CreateContext(WriteAndReadEnum writeAndRead)
    {
        string connectionString = string.Empty;
        switch (writeAndRead)
        {
            case WriteAndReadEnum.Write:
                connectionString = Configuration.GetConnectionString("EFCoreTestToWrite");
                break;
            case WriteAndReadEnum.Read:
                connectionString = GetReadConnectionString();
                break;
            default:
                break;
        }
        return new EFCoreContext(connectionString);
    }

    private string GetReadConnectionString()
    {
        /*
         * 随机策略
         * 权重策略
         * 轮询策略
         */

        //随机策略
        string connectionString = ReadConnectionStrings[new Random().Next(0, ReadConnectionStrings.Length)];

        return connectionString;
    }
}

Models层完成

 

在Web层中

在Startup的ConfigureServices方法添加依赖注入

services.AddScoped();

操作

public class HomeController : Controller
{
    private readonly ILogger _logger;

    public IDbContextFactory DbContextFactory { get; }

    public HomeController(ILogger logger,IDbContextFactory dbContextFactory)
    {
        _logger = logger;
        DbContextFactory = dbContextFactory;
    }

    public IActionResult Index()
    {
        //写入操作
        EFCoreContext writeContext = DbContextFactory.CreateContext(WriteAndReadEnum.Write);
        writeContext.UserInfo.Add(new UserInfo() { Name = "AA", Age = 20 });
        writeContext.SaveChanges();

        //查询操作
        EFCoreContext readContext = DbContextFactory.CreateContext(WriteAndReadEnum.Read);
        UserInfo userInfo = readContext.UserInfo.OrderByDescending(u => u.Id).FirstOrDefault();

        return View();
    }
}

 

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