From ASP.NET App Suspend – responsive shared .NET web hosting

Suspend is the new terminate

ASP.NET App Suspend is a new feature in the .NET Framework 4.5.1 that makes ASP.NET sites much more responsive and enables you to host more sites on a single server. It is very well suited for commercial web hosters, like Windows Azure Web Sites, and Enterprise IT web hosting.

ASP.NET App Suspend is a self-tuning mechanism for web hosting, a little bit like CLR GC generations (if you squint). The addition of suspend establishes three states that a site can be in on a given machine. You can see the three states in the diagram, below.


All sites start out as inactive. As sites are requested, they are loaded into memory, become active, and respond to page requests. After sites have been idle, as determined by the timeout setting, they will be suspended. Suspended sites effectively lose access to the CPU, making CPU cycles and most of the memory they were using available for requests to other sites. However, they are kept in a state – this is the new suspended state – by which they can be resumed very quickly and respond to traffic again.

Usage scenarios

Scenarios that can benefit from ASP.NET App Suspend.

  • Shared hosting (commercial hosting or enterprise IT)        Companies selling or taking advantage of shared hosting can pack many more sites on a given machine, while providing much more responsive site experience.
  • Switch to shared hosting        Web site owners can take advantage of low-cost shared hosting while delivering the responsive experience that they want.
  • Hot spare for large sites        Large high-traffic sites can maintain spares in suspend, ready for when one of the servers behind a load balancer goes down (planned or unplanned).
  • Disaster recovery        Large high-traffic sites can maintain spares in suspend in a backup datacenter, ready for when the main data center goes down or otherwise becomes inaccessible.


ASP.NET App Suspend is a new feature for ASP.NET, available in the .NET Framework 4.5.1 on Windows Server 2012 R2. It delivers much better startup responsiveness for sites that do not get consistent traffic and would otherwise not be kept loaded in a responsive state at all times.


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