读写分离¶

随着系统用户的增多，系统的查询压力会越来越大，此时使用读写分离方案，可以有效缓解数据库的查询压力。

前提条件¶

sharding-core 未实现数据同步到只读库的功能，要采用读写分离的方案，需要先做好数据库的数据同步机制，例如 MySQL 的 binlog 同步、MSSQL 的 always on功能等。

配置读写分离¶

要使用sharding-core,需要修改DbContext的注册方式。

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); });
    });

使用 AddShardingDbContext 注册,下面配置为名称为ds0的数据源配置了两个只读库：

builder.Services.AddShardingDbContext<ApplicationDbContext>()
        .UseConfig(op =>
        {
            op.ThrowIfQueryRouteNotMatch = true;
            op.UseShardingQuery((conStr, builder) =>
            {
                builder.UseMySql(conStr,
                    new MySqlServerVersion(new Version(8, 0, 34)));
            });
            op.UseShardingTransaction((con, builder) =>
            {
                builder.UseMySql(con,
                    new MySqlServerVersion(new Version(8, 0, 34)));
            });
            op.AddDefaultDataSource("ds0", builder.Configuration.GetConnectionString("Mysql")); //配置写库
            op.AddReadWriteSeparation(sp => new Dictionary<string, IEnumerable<string>>    //配置只读库
                {
                    {
                        "ds0",
                        [builder.Configuration.GetConnectionString("Mysql-Read1"), builder.Configuration.GetConnectionString("Mysql-Read2")]
                    }
                },
                readStrategyEnum: ReadStrategyEnum.Loop,
                defaultEnableBehavior: ReadWriteDefaultEnableBehavior.DefaultDisable,
                defaultPriority: 10,
                readConnStringGetStrategy: ReadConnStringGetStrategyEnum.LatestFirstTime
            );
        })
        .ReplaceService<IDbContextCreator, ApplicationDbContextCreator>()
        .AddShardingCore();

读写分离¶

前提条件¶

配置读写分离¶

参考文档¶