Multi-Tenancy
Multi-Tenancy is a widely used architecture to create SaaS applications where the hardware and software resources are shared by the customers (tenants). ABP Framework provides all the base functionalities to create multi tenant applications.
Wikipedia defines the multi-tenancy as like that:
Software Multi-tenancy refers to a software architecture in which a single instance of software runs on a server and serves multiple tenants. A tenant is a group of users who share a common access with specific privileges to the software instance. With a multitenant architecture, a software application is designed to provide every tenant a dedicated share of the instance including its data, configuration, user management, tenant individual functionality and non-functional properties. Multi-tenancy contrasts with multi-instance architectures, where separate software instances operate on behalf of different tenants.
Terminology: Host vs Tenant
There are two main side of a typical SaaS / Multi-tenant application:
- A Tenant is a customer of the SaaS application that pays money to use the service.
- Host is the company that owns the SaaS application and manages the system.
The Host and the Tenant terms will be used for that purpose in the rest of the document.
Configuration
AbpMultiTenancyOptions: Enable/Disable Multi-Tenancy
AbpMultiTenancyOptions
is the main options class to enable/disable the multi-tenancy for your application.
Example: Enable multi-tenancy
Configure<AbpMultiTenancyOptions>(options =>
{
options.IsEnabled = true;
});
Multi-Tenancy is disabled in the ABP Framework by default. However, it is enabled by default when you create a new solution using the startup template.
MultiTenancyConsts
class in the solution has a constant to control it in a single place.
Database Architecture
ABP Framework supports all the following approaches to store the tenant data in the database;
- Single Database: All tenants are stored in a single database.
- Database per Tenant: Every tenant has a separate, dedicated database to store the data related to that tenant.
- Hybrid: Some tenants share a single databases while some tenants may have their own databases.
Tenant management module (which comes pre-installed with the startup projects) allows you to set a connection string for any tenant (as optional), so you can achieve any of the approaches.
Usage
Multi-tenancy system is designed to work seamlessly and make your application code multi-tenancy unaware as much as possible.
IMultiTenant
You should implement the IMultiTenant
interface for your entities to make them multi-tenancy ready.
Example: A multi-tenant Product entity
using System;
using Volo.Abp.Domain.Entities;
using Volo.Abp.MultiTenancy;
namespace MultiTenancyDemo.Products
{
public class Product : AggregateRoot<Guid>, IMultiTenant
{
public Guid? TenantId { get; set; } //Defined by the IMultiTenant interface
public string Name { get; set; }
public float Price { get; set; }
}
}
IMultiTenant
interface just defines a TenantId
property. When you implement this interface, ABP Framework automatically filters entities for the current tenant when you query from database. So, you don't need to manually add TenantId
condition while performing queries. A tenant can not access to data of another tenant by default.
Why the TenantId Property is Nullable?
IMultiTenant.TenantId
is nullable. When it is null that means the entity is owned by the Host side and not owned by a tenant. It is useful when you create a functionality in your system that is both used by the tenant and the host sides.
For example, IdentityUser
is an entity defined by the Identity Module. The host and all the tenants have their own users. So, for the host side, users will have a null
TenantId
while tenant users will have their related TenantId
.
Tip: If your entity is tenant-specific and has no meaning in the host side, you can force to not set
null
for theTenantId
in the constructor of your entity.
When to set the TenantId?
ABP automatically sets the TenantId
for you when you create a new entity object. It is done in the constructor of the base Entity
class (all other base entity and aggregate root classes are derived from the Entity
class). The TenantId
is set from the current value of the ICurrentTenant.Id
property (see the next section).
If you set the TenantId
value for a specific entity object, it will override the value set by the base class. If you want to set the TenantId
property yourself, we recommend to do it in the constructor of your entity class and do not change (update) it again (Actually, changing it means that you are moving the entity from a tenant to another tenant. If you want that, you need an extra care about the related entities in the database).
ICurrentTenant
ICurrentTenant
is the main service to interact with the multi-tenancy infrastructure.
ApplicationService
, DomainService
, AbpController
and some other base classes already has pre-injected CurrentTenant
properties. For other type of classes, you can inject the ICurrentTenant
into your service.
Tenant Properties
ICurrentTenant
defines the following properties;
Id
(Guid
): Id of the current tenant. Can benull
if the current user is a host user or the tenant could not be determined from the request.Name
(string
): Name of the current tenant. Can benull
if the current user is a host user or the tenant could not be determined from the request.IsAvailable
(bool
): Returnstrue
if theId
is notnull
.
Change the Current Tenant
ABP Framework automatically filters the resources (database, cache...) based on the ICurrentTenant.Id
. However, in some cases you may want to perform an operation on behalf of a specific tenant, generally when you are in the host context.
ICurrentTenant.Change
method changes the current tenant for a limited scope, so you can safely perform operations for the tenant.
Example: Get product count of a specific tenant
using System;
using System.Threading.Tasks;
using Volo.Abp.Domain.Repositories;
using Volo.Abp.Domain.Services;
namespace MultiTenancyDemo.Products
{
public class ProductManager : DomainService
{
private readonly IRepository<Product, Guid> _productRepository;
public ProductManager(IRepository<Product, Guid> productRepository)
{
_productRepository = productRepository;
}
public async Task<long> GetProductCountAsync(Guid? tenantId)
{
using (CurrentTenant.Change(tenantId))
{
return await _productRepository.GetCountAsync();
}
}
}
}
Change
method can be used in a nested way. It restores theCurrentTenant.Id
to the previous value after theusing
statement.- When you use
CurrentTenant.Id
inside theChange
scope, you get thetenantId
provided to theChange
method. So, the repository also get thistenantId
and can filter the database query accordingly. - Use
CurrentTenant.Change(null)
to change scope to the host context.
Always use the
Change
method with ausing
statement like done in this example.
Data Filtering: Disable the Multi-Tenancy Filter
As mentioned before, ABP Framework handles data isolation between tenants using the Data Filtering system. In some cases, you may want to disable it and perform a query on all the data, without filtering for the current tenant.
Example: Get count of products in the database, including all the products of all the tenants.
using System;
using System.Threading.Tasks;
using Volo.Abp.Data;
using Volo.Abp.Domain.Repositories;
using Volo.Abp.Domain.Services;
using Volo.Abp.MultiTenancy;
namespace MultiTenancyDemo.Products
{
public class ProductManager : DomainService
{
private readonly IRepository<Product, Guid> _productRepository;
private readonly IDataFilter _dataFilter;
public ProductManager(
IRepository<Product, Guid> productRepository,
IDataFilter dataFilter)
{
_productRepository = productRepository;
_dataFilter = dataFilter;
}
public async Task<long> GetProductCountAsync()
{
using (_dataFilter.Disable<IMultiTenant>())
{
return await _productRepository.GetCountAsync();
}
}
}
}
See the Data Filtering document for more.
Note that this approach won't work if your tenants have separate databases since there is no built-in way to query from multiple database in a single database query. You should handle it yourself if you need it.
Infrastructure
Determining the Current Tenant
The first thing for a multi-tenant application is to determine the current tenant on the runtime.
ABP Framework provides an extensible Tenant Resolving system for that purpose. Tenant Resolving system then used in the Multi-Tenancy Middleware to determine the current tenant for the current HTTP request.
Tenant Resolvers
Default Tenant Resolvers
The following resolvers are provided and configured by default;
CurrentUserTenantResolveContributor
: Gets the tenant id from claims of the current user, if the current user has logged in. This should always be the first contributor for the security.QueryStringTenantResolveContributor
: Tries to find current tenant id from query string parameters. The parameter name is__tenant
by default.RouteTenantResolveContributor
: Tries to find current tenant id from route (URL path). The variable name is__tenant
by default. If you defined a route with this variable, then it can determine the current tenant from the route.HeaderTenantResolveContributor
: Tries to find current tenant id from HTTP headers. The header name is__tenant
by default.CookieTenantResolveContributor
: Tries to find current tenant id from cookie values. The cookie name is__tenant
by default.
Problems with the NGINX
You may have problems with the __tenant
in the HTTP Headers if you're using the nginx as the reverse proxy server. Because it doesn't allow to use underscore and some other special characters in the HTTP headers and you may need to manually configure it. See the following documents please:
http://nginx.org/en/docs/http/ngx_http_core_module.html#ignore_invalid_headers
http://nginx.org/en/docs/http/ngx_http_core_module.html#underscores_in_headers
AbpAspNetCoreMultiTenancyOptions
__tenant
parameter name can be changed using AbpAspNetCoreMultiTenancyOptions
.
Example:
services.Configure<AbpAspNetCoreMultiTenancyOptions>(options =>
{
options.TenantKey = "MyTenantKey";
});
If you change the TenantKey
, make sure to pass it to CoreModule
in the Angular client as follows:
@NgModule({
imports: [
CoreModule.forRoot({
// ...
tenantKey: 'MyTenantKey'
}),
],
// ...
})
export class AppModule {}
If you need to access it, you can inject it as follows:
import { Inject } from '@angular/core';
import { TENANT_KEY } from '@abp/ng.core';
class SomeComponent {
constructor(@Inject(TENANT_KEY) private tenantKey: string) {}
}
However, we don't suggest to change this value since some clients may assume the the
__tenant
as the parameter name and they might need to manually configure then.
The MultiTenancyMiddlewareErrorPageBuilder
is used to handle inactive and non-existent tenants.
It will respond to an error page by default, you can change it if you want, eg: only output the error log and continue ASP NET Core's request pipeline.
Configure<AbpAspNetCoreMultiTenancyOptions>(options =>
{
options.MultiTenancyMiddlewareErrorPageBuilder = async (context, exception) =>
{
// Handle the exception.
// Return true to stop the pipeline, false to continue.
return true;
};
});
Domain/Subdomain Tenant Resolver
In a real application, most of times you will want to determine current tenant either by subdomain (like mytenant1.mydomain.com) or by the whole domain (like mytenant.com). If so, you can configure the AbpTenantResolveOptions
to add the domain tenant resolver.
Example: Add a subdomain resolver
Configure<AbpTenantResolveOptions>(options =>
{
options.AddDomainTenantResolver("{0}.mydomain.com");
});
{0}
is the placeholder to determine current tenant's unique name.- Add this code to the
ConfigureServices
method of your module. - This should be done in the Web/API Layer since the URL is a web related stuff.
There is an example that uses the subdomain to determining the current tenant.
Custom Tenant Resolvers
You can add implement your custom tenant resolver and configure the AbpTenantResolveOptions
in your module's ConfigureServices
method as like below:
Configure<AbpTenantResolveOptions>(options =>
{
options.TenantResolvers.Add(new MyCustomTenantResolveContributor());
});
MyCustomTenantResolveContributor
must inherit from the TenantResolveContributorBase
(or implement the ITenantResolveContributor
) as shown below:
using System.Threading.Tasks;
using Volo.Abp.MultiTenancy;
namespace MultiTenancyDemo.Web
{
public class MyCustomTenantResolveContributor : TenantResolveContributorBase
{
public override string Name => "Custom";
public override Task ResolveAsync(ITenantResolveContext context)
{
//TODO...
}
}
}
- A tenant resolver should set
context.TenantIdOrName
if it can determine it. If not, just leave it as is to allow the next resolver to determine it. context.ServiceProvider
can be used if you need to additional services to resolve from the dependency injection system.
Multi-Tenancy Middleware
Multi-Tenancy middleware is an ASP.NET Core request pipeline middleware that determines the current tenant from the HTTP request and sets the ICurrentTenant
properties.
Multi-Tenancy middleware is typically placed just under the authentication middleware (app.UseAuthentication()
):
app.UseMultiTenancy();
This middleware is already configured in the startup templates, so you normally don't need to manually add it.
Tenant Store
ITenantStore
is used to get the tenant configuration from a data source.
Tenant Management Module
The tenant management module is included in the startup templates and implements the ITenantStore
interface to get the tenants and their configuration from a database. It also provides the necessary functionality and UI to manage the tenants and their connection strings.
Configuration Data Store
If you don't want to use the tenant management module, the DefaultTenantStore
is used as the ITenantStore
implementation. It gets the tenant configurations from the configuration system (IConfiguration
). You can either configure the AbpDefaultTenantStoreOptions
options or set it in your appsettings.json
file:
Example: Define tenants in appsettings.json
"Tenants": [
{
"Id": "446a5211-3d72-4339-9adc-845151f8ada0",
"Name": "tenant1"
},
{
"Id": "25388015-ef1c-4355-9c18-f6b6ddbaf89d",
"Name": "tenant2",
"ConnectionStrings": {
"Default": "...tenant2's db connection string here..."
}
}
]
It is recommended to use the Tenant Management module, which is already pre-configured when you create a new application with the ABP startup templates.
Other Multi-Tenancy Infrastructure
ABP Framework was designed to respect to the multi-tenancy in every aspect and most of the times everything will work as expected.
BLOB Storing, Caching, Data Filtering, Data Seeding, Authorization and all the other services are designed to properly work in a multi-tenant system.
The Tenant Management Module
ABP Framework provides all the the infrastructure to create a multi-tenant application, but doesn't make any assumption about how you manage (create, delete...) your tenants.
The Tenant Management module provides a basic UI to manage your tenants and set their connection strings. It is pre-configured for the application startup template.