基于Citus和ASP.NET Core开发多租户应用
Citus是基于PsotgreSQL的扩展，用于切分PsotgreSQL的数据，非常简单地实现数据“切片（sharp）”。如果不使用Citus，则需要开发者自己实现分布式数据访问层（DDAL），实现路由和结果汇总等逻辑，借助Citus可简化开发，是开发者把精力集中在具体的业务逻辑上。
对于多租户程序来说，Citus可以帮助企业对数据进行切片，相比于传统的数据管理方式，Citus更智能，操作更为简单，运维成本更低廉。下面演示Citus的简单使用。
Step 01 安装docker和docker-compose（以Docker方式部署Citus）
curl -sSL https://get.docker.com/ | shsudo usermod -aG docker $USER && exec sg docker newgrp `id -gn` sudo systemctl start docker sudo curl -sSL https://github.com/docker/compose/releases/download/1.19.0/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-composesudo chmod +x /usr/local/bin/docker-compose
Step 02 安装并启动Citus
Citus有3个版本Citus Community，Citus Cloud（云端版）， Citus Enterprise（支持HA等高级特性），本文使用Citus Community。
curl -sSLO https://raw.githubusercontent.com/citusdata/docker/master/docker-compose.ymldocker-compose -p citus up -d
Step 03 连接postgres
docker exec -it citus_master psql -U postgres
Step 04 设置数据库用户密码
postgres=# \password postgres #给postgres用户设置密码 Enter new password: Enter it again:
Step 05 创建表
CREATE TABLE tenants (
id uuid NOT NULL,
domain text NOT NULL,
name text NOT NULL,
description text NOT NULL,
created_at timestamptz NOT NULL,
updated_at timestamptz NOT NULL
);
CREATE TABLE questions (
id uuid NOT NULL,
tenant_id uuid NOT NULL,
title text NOT NULL,
votes int NOT NULL,
created_at timestamptz NOT NULL,
updated_at timestamptz NOT NULL
);
ALTER TABLE tenants ADD PRIMARY KEY (id);
ALTER TABLE questions ADD PRIMARY KEY (id, tenant_id);
Step 06 告知Citus如何对数据进行切片
SELECT create_distributed_table('tenants', 'id');
SELECT create_distributed_table('questions', 'tenant_id');
Step 07 初始化数据
INSERT INTO tenants VALUES (
'c620f7ec-6b49-41e0-9913-08cfe81199af',
'bufferoverflow.local',
'Buffer Overflow',
'Ask anything code-related!',
now(),
now());
INSERT INTO tenants VALUES (
'b8a83a82-bb41-4bb3-bfaa-e923faab2ca4',
'dboverflow.local',
'Database Questions',
'Figure out why your connection string is broken.',
now(),
now());
INSERT INTO questions VALUES (
'347b7041-b421-4dc9-9e10-c64b8847fedf',
'c620f7ec-6b49-41e0-9913-08cfe81199af',
'How do you build apps in ASP.NET Core?',
1,
now(),
now());
INSERT INTO questions VALUES (
'a47ffcd2-635a-496e-8c65-c1cab53702a7',
'b8a83a82-bb41-4bb3-bfaa-e923faab2ca4',
'Using postgresql for multitenant data?',
2,
now(),
now());
Step 08 新建ASP.NET Core Web应用程序，并添加引用
安装“Npgsql.EntityFrameworkCore.PostgreSQL”包
Npgsql.EntityFrameworkCore.PostgreSQL：支持Entity Framework Core操作PostgreSQL。
安装“SaasKit.Multitenancy”包
SaasKit.Multitenancy：支持ASP.NET Core开发多租户应用。
Step 09 创建models
using System;
namespace QuestionExchange.Models
{
public class Question
{
public Guid Id { get; set; }
public Tenant Tenant { get; set; }
public string Title { get; set; }
public int Votes { get; set; }
public DateTimeOffset CreatedAt { get; set; }
public DateTimeOffset UpdatedAt { get; set; }
}
}
using System;
namespace QuestionExchange.Models
{
public class Tenant
{
public Guid Id { get; set; }
public string Domain { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public DateTimeOffset CreatedAt { get; set; }
public DateTimeOffset UpdatedAt { get; set; }
}
}
using System.Collections.Generic;
namespace QuestionExchange.Models
{
public class QuestionListViewModel
{
public IEnumerable
}
}
Step 10 创建数据上下文
using System.Linq;
using Microsoft.EntityFrameworkCore;
using QuestionExchange.Models;
namespace QuestionExchange
{
public class AppDbContext : DbContext
{
public AppDbContext(DbContextOptions
: base(options)
{
}
public DbSet
public DbSet
///
/// C# classes and properties are PascalCase by convention, but your Postgres tables and columns are lowercase (and snake_case).
/// The OnModelCreating method lets you override the default name translation and let Entity Framework Core know how to find
/// the entities in your database.
///
///
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
var mapper = new Npgsql.NpgsqlSnakeCaseNameTranslator();
var types = modelBuilder.Model.GetEntityTypes().ToList();
// Refer to tables in snake_case internally
types.ForEach(e => e.Relational().TableName = mapper.TranslateMemberName(e.Relational().TableName));
// Refer to columns in snake_case internally
types.SelectMany(e => e.GetProperties())
.ToList()
.ForEach(p => p.Relational().ColumnName = mapper.TranslateMemberName(p.Relational().ColumnName));
}
}
}
Step 11 为SaaSKit实现解析器
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging;
using SaasKit.Multitenancy;
using QuestionExchange.Models;
namespace QuestionExchange
{
public class CachingTenantResolver : MemoryCacheTenantResolver
{
private readonly AppDbContext _context;
public CachingTenantResolver(
AppDbContext context, IMemoryCache cache, ILoggerFactory loggerFactory)
: base(cache, loggerFactory)
{
_context = context;
}
// Resolver runs on cache misses
protected override async Task
{
var subdomain = context.Request.Host.Host.ToLower();
var tenant = await _context.Tenants
.FirstOrDefaultAsync(t => t.Domain == subdomain);
if (tenant == null) return null;
return new TenantContext
}
protected override MemoryCacheEntryOptions CreateCacheEntryOptions()
=> new MemoryCacheEntryOptions().SetAbsoluteExpiration(TimeSpan.FromHours(2));
protected override string GetContextIdentifier(HttpContext context)
=> context.Request.Host.Host.ToLower();
protected override IEnumerable
=> new string[] { context.Tenant.Domain };
}
}
Step 12 修改Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using QuestionExchange.Models;
namespace QuestionExchange
{
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
var connectionString = "Server=192.168.99.102;Port=5432;Database=postgres;Userid=postgres;Password=yourpassword;";
services.AddEntityFrameworkNpgsql()
.AddDbContext
services.AddMultitenancy
services.AddMvc();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
app.UseBrowserLink();
}
else
{
app.UseExceptionHandler("/Home/Error");
}
app.UseStaticFiles();
app.UseMultitenancy
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
}
}
}
Step 13 创建View和Controller
@inject Tenant Tenant
@model QuestionListViewModel
@{
ViewData["Title"] = "Home Page";
}
Welcome to @Tenant.Name
@Tenant.Description
Popular questions
- @question.Title
@foreach (var question in Model.Questions)
{
}
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using QuestionExchange.Models;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
namespace QuestionExchange.Controllers
{
public class HomeController : Controller
{
private readonly AppDbContext _context;
private readonly Tenant _currentTenant;
public HomeController(AppDbContext context, Tenant tenant)
{
_context = context;
_currentTenant = tenant;
}
public async Task
{
var topQuestions = await _context
.Questions
.Where(q => q.Tenant.Id == _currentTenant.Id)
.OrderByDescending(q => q.UpdatedAt)
.Take(5)
.ToArrayAsync();
var viewModel = new QuestionListViewModel
{
Questions = topQuestions
};
return View(viewModel);
}
public IActionResult About()
{
ViewData["Message"] = "Your application description page.";
return View();
}
public IActionResult Contact()
{
ViewData["Message"] = "Your contact page.";
return View();
}
public IActionResult Error()
{
return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
}
}
}
Step 14 运行站点
首先需要修改本地Hosts文件，添加：
127.0.0.1 bufferoverflow.local127.0.0.1 dboverflow.local
运行cmd（命令行），输入以下命令，刷新DNS：
ipconfig /flushdns
分别使用不同Url浏览站点，可以看到之前插入的测试数据在不同租户下显示不同：
以上，简单演示了如何基于Citus开发多租户应用。此外，Citus还比较适合开发需要快速返回查询结果的应用（比如“仪表板”等）。
本文演示的例子比较简单，仅仅是演示了使用Citus开发多租户应用的可能。具体实践中，还涉及到具体业务以及数据库切片技巧等。建议阅读微软的《Cloud Design Patterns Book》中的Sharding模式部分，以及Citus的官方技术文档。
参考资料：
https://github.com/citusdata/citus
https://www.citusdata.com/blog/2018/01/22/multi-tenant-web-apps-with-dot-net-core-and-postgres
https://docs.citusdata.com/en/v7.1/aboutcitus/what_is_citus.html
原文地址:https://www.cnblogs.com/MeteorSeed/p/8446154.html
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