This article discusses some of
the issues that surround architecting and building multi-tenant
applications to run on Windows Azure™ technology platform. A highly scalable,
cloud-based platform offers a compelling set of features for building
services that many users will pay a subscription to use. A multi-tenant
architecture where multiple users share the application enables
economies of scale as users share resources, but at the cost of a more
complex application that has to manage multiple users independently of
each other.
1. Single-Tenant vs.
Multi-Tenant
One of the
first architectural decisions that the team at Tailspin had to make
about the Surveys application was whether it should be a single-tenant
or multi-tenant application to best support multiple customers. Figure 1 shows the difference between these
approaches at a high-level. The single-tenant model has a separate,
logical instance of the application for each customer, while the
multi-tenant model has a single logical instance of the application
shared by many customers. It’s important to note that the multi-tenant
model still offers separate views of the application’s data to its
users. In the Surveys application, ClientB must not be able to see or
modify ClientA’s surveys or data. Tailspin, as the owner of the
application, will have full access to all the data stored in the
application.
2.2.
Multi-Tenancy Architecture in Azure
In Windows Azure, the distinction between the
multi-tenant model and the single-tenant model is not as straightforward
as the model in Figure 1 because an application in Windows
Azure can be made up of multiple components, each of which can be
single-tenanted or multi-tenanted. For example, if an application has a
user interface (UI) component, a services component, and a storage
component, a possible design could look like that shown in Figure 2.
|
| This diagram
shows logical instances of the Surveys application. In practice, you can
implement each logical instance as multiple physical instances to scale
the application |
This is not the only
possible design, but it illustrates that you don’t have to make the same
choice of either single-tenancy or multi-tenancy
model for every component in your application.
Should you design your
Windows Azure application to be single-tenant or multi-tenant? There’s no right or wrong
answer, but as you will see in the following section, there are a number
of factors that can influence your choice.
