按租户分库¶

按租户分库，是更具体的分库策略场景，在这个场景中大部分的业务处理都是限定在租户范围内的，因此可以保持在同一事务内提交。

配置分库¶

添加包NetCorePal.Extensions.ShardingCore引用：

dotnet add package NetCorePal.Extensions.ShardingCore

或者 PackageReference

<PackageReference Include="NetCorePal.Extensions.ShardingCore" />

为你的 DbContext 类型添加 IShardingCore 接口

public partial class ApplicationDbContext : AppDbContextBase, IShardingCore
{
    //Your Code
}

创建ApplicationDbContextCreator

public class ApplicationDbContextCreator(IShardingProvider provider)
    : IDbContextCreator
{
    public DbContext CreateDbContext(DbContext shellDbContext, ShardingDbContextOptions shardingDbContextOptions)
    {
        var outDbContext = (ApplicationDbContext)shellDbContext;
        var dbContext = new ApplicationDbContext(
            (DbContextOptions<ApplicationDbContext>)shardingDbContextOptions.DbContextOptions, outDbContext.Mediator);
        if (dbContext is IShardingTableDbContext shardingTableDbContext)
        {
            shardingTableDbContext.RouteTail = shardingDbContextOptions.RouteTail;
        }

        _ = dbContext.Model;
        return dbContext;
    }

    public DbContext GetShellDbContext(IShardingProvider shardingProvider)
    {
        return shardingProvider.GetRequiredService<ApplicationDbContext>();
    }
}

移除 AddDbContext 注册方式

builder.Services.AddDbContext<ApplicationDbContext>(options =>
    {
        options.UseMySql(builder.Configuration.GetConnectionString("Mysql"),
            new MySqlServerVersion(new Version(8, 0, 34)),
            b => { b.MigrationsAssembly(typeof(Program).Assembly.FullName); });
    });

添加包 NetCorePal.Extensions.DistributedTransactions.CAP.MySql 以支持CAP的发布消息分库：

dotnet add package NetCorePal.Extensions.DistributedTransactions.CAP.MySql

为 ApplicationDbContext 添加 IMySqlCapDataStorage 接口

public partial class ApplicationDbContext : AppDbContextBase, 
   IShardingCore, IMySqlCapDataStorage
{
    //Your Code
}

修改AddCap代码，配置UseNetCorePalStorage

services.AddCap(op =>
{
   op.UseNetCorePalStorage<ShardingDatabaseDbContext>(); //配置使用UseNetCorePalStorage 以支持分库
   op.UseRabbitMQ(p =>
   {
      p.HostName = _rabbitMqContainer.Hostname;
      p.UserName = "guest";
      p.Password = "guest";
      p.Port = _rabbitMqContainer.GetMappedPublicPort(5672);
      p.VirtualHost = "/";
   });
});

MS SqlServer 以及 PostgreSql 也可以使用对应的包来支持

dotnet add package NetCorePal.Extensions.DistributedTransactions.CAP.SqlServer
dotnet add package NetCorePal.Extensions.DistributedTransactions.CAP.PostgreSql

配置MediatR添加AddTenantShardingBehavior,注意需要添加在AddUnitOfWorkBehaviors之前:

services.AddMediatR(cfg =>
                 cfg.RegisterServicesFromAssembly(typeof(ShardingDatabaseDbContextTests).Assembly)
                     .AddTenantShardingBehavior()    //添加在`AddUnitOfWorkBehaviors`之前
                     .AddUnitOfWorkBehaviors());

为分库的实体添加分库路由配置，分库需要实现基类NetCorePalTenantVirtualDataSourceRoute:

public class OrderTenantVirtualDataSourceRoute(
     IOptions<NetCorePalShardingCoreOptions> options,
     ITenantDataSourceProvider provider) : 
     NetCorePalTenantVirtualDataSourceRoute<Order, string>(options, provider)
{
     public override void Configure(EntityMetadataDataSourceBuilder<Order> builder)
     {
          builder.ShardingProperty(p => p.TenantId); //返回租户Id
     }
}

配置ShardingCore:

services.AddShardingDbContext<ShardingDatabaseDbContext>()
                 .UseNetCorePal(op =>  //配置分库名称，需要UseConfig中配置的名称保持一致
                 {
                     op.AllDataSourceNames = ["Db0", "Db1"];
                     op.DefaultDataSourceName = "Db0";
                 })
                 .UseRouteConfig(op =>
                 {
                     op.AddCapShardingDataSourceRoute();  //添加默认的PubishedMessage分库路由
                     op.AddShardingDataSourceRoute<OrderTenantVirtualDataSourceRoute>();  //添加实体分库路由
                 }).UseConfig(op =>
                 {
                     op.ThrowIfQueryRouteNotMatch = true;
                     op.UseShardingQuery((conStr, builder) =>
                     {
                         builder.UseMySql(conStr,
                             new MySqlServerVersion(new Version(8, 0, 34)));
                     });
                     op.UseShardingTransaction((conStr, builder) =>
                     {
                         builder.UseMySql(conStr,
                             new MySqlServerVersion(new Version(8, 0, 34)));
                     });
                     op.AddDefaultDataSource("Db0", _mySqlContainer0.GetConnectionString());
                     op.AddExtraDataSource(_ => new Dictionary<string, string>
                     {
                         { "Db1", _mySqlContainer1.GetConnectionString() }
                     });
                 })
                 .ReplaceService<IDbContextCreator, ShardingDatabaseDbContextCreator>()
                 .AddShardingCore();

配置租户上下文支持，添加包NetCorePal.Context.Shared:
```
 dotnet add package NetCorePal.Context.Shared
```
注册租户上下文以及CAP上下文处理器：
```
services.AddTenantContext().AddCapContextProcessor();
```

配置CAP上下文支持：

services.AddIntegrationEvents(typeof(ShardingTenantDbContext))
                 .UseCap<ShardingTenantDbContext>(capbuilder =>
                 {
                     capbuilder.AddContextIntegrationFilters(); //添加租户上下文过滤器
                     capbuilder.RegisterServicesFromAssemblies(typeof(ShardingTenantDbContext));
                 });

实现ITenantDataSourceProvider并注册：

public class MyTenantDataSourceProvider : ITenantDataSourceProvider
{
   public string GetDataSourceName(string tenantId)
   {
       return "Db" + (long.Parse(tenantId) % 10);  //实现租户Id与数据源名称的对应逻辑
   }
}

注册租户数据源提供程序：

services.AddSingleton<ITenantDataSourceProvider, MyTenantDataSourceProvider>();

使用租户上下文¶

在配置完成后，需要操作租户数据时，需要在 Command 发出前完成租户上下文的初始化，使用IContextAccessor设置当前上下文：

//根据用户请求获取租户Id
var tenantId = currentUser.TenantId;
var contextAccessor = scope.ServiceProvider.GetRequiredService<IContextAccessor>();
contextAccessor.SetContext(new TenantContext(tenantId));

一般建议在中间件中完成租户上下文的设置：

public class TenantMiddleware
{
    private readonly RequestDelegate _next;

    public TenantMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context, IContextAccessor contextAccessor)
    {
        var tenantId = context.Request.Headers["TenantId"].ToString();
        if (!string.IsNullOrEmpty(tenantId))
        {
            contextAccessor.SetContext(new TenantContext(tenantId));
        }
        await _next(context);
    }
}

高级¶

更多分库配置请参考官方文档：https://xuejmnet.github.io/sharding-core-doc/sharding-data-source/init/