Self-Hosting in a
Managed Application
WCF services can be hosted in any managed application. This
is the most flexible option because it requires the least infrastructure to
deploy. You embed the code for the service inside the managed application code
and then create and open an instance of the ServiceHost to make the service
available.
This option enables two common scenarios: WCF services
running inside console applications and rich client applications such as those
based on Windows Presentation Foundation (WPF) or Windows Forms (WinForms).
Hosting a WCF service inside a console application is typically useful during
the application's development phase. This makes them easy to debug, easy to get
trace information from to find out what is happening inside of the application,
and easy to move around by copying them to new locations. This hosting option
also makes it easy for rich client applications, such as WPF and WinForms
applications, to communicate with the outside world. For example, a
peer-to-peer collaboration client that uses WPF for its user interface and also
hosts a WCF service that allows other clients to connect to it and share
information.
Benefits: Flexible, Easy to deploy, Not an enterprise
solution for services.
Managed Windows
Services
This hosting option consists of registering the application
domain (AppDomain) that hosts an WCF service as a managed Windows Service
(formerly known as NT service) so that the process lifetime of the service is
controlled by the service control manager (SCM) for Windows services. Like the
self-hosting option, this type of hosting environment requires that some
hosting code is written as part of the application. The service is implemented
as both a Windows Service and as an WCF service by causing it to inherit from
the ServiceBase class as well as from an WCF service contract interface. The
ServiceHost is then created and opened within an overridden OnStart method and
closed within an overridden OnStop method. An installer class that inherits
from Installer must also be implemented to allow the program to be installed as
a Windows Service by the Installutil.exe tool. The scenario enabled by the
managed Windows Service hosting option is that of a long-running WCF service
hosted outside of IIS in a secure environment that is not message-activated.
The lifetime of the service is controlled instead by the operating system. This
hosting option is available in all versions of Windows.
Benefits: Service process lifetime controlled by the
operating system, not message-activated, Supported by all versions of Windows, Secure
environment.
Internet Information
Services (IIS)
The IIS hosting option is integrated with ASP.NET and uses
the features these technologies offer, such as process recycling, idle
shutdown, process health monitoring, and message-based activation. On the
Windows XP and Windows Server 2003 operating systems, this is the preferred
solution for hosting Web service applications that must be highly available and
highly scalable. IIS also offers the integrated manageability that customers
expect from an enterprise-class server product. This hosting option requires
that IIS be properly configured, but it does not require that any hosting code
be written as part of the application
Note that IIS-hosted services can only use the HTTP
transport. Its implementation in IIS 5.1 has introduced some limitations in
Windows XP. The message-based activation provided for an WCF service by IIS 5.1
on Windows XP blocks any other self-hosted WCF service on the same computer
from using port 80 to communicate. WCF services can run in the same
AppDomain/Application Pool/Worker Process as other applications when hosted by
IIS 6.0 on Windows Server 2003. But because WCF and IIS 6.0 both use the
kernel-mode HTTP stack (HTTP.sys), IIS 6.0 can share port 80 with other
self-hosted WCF services running on the same machine, unlike IIS 5.1.
Benefits: Process recycling, Idle shutdown, Process health
monitoring, Message-based activation, HTTP only.
Windows Process
Activation Service (WAS)
Windows Process Activation Service (WAS) is the new process
activation mechanism for the Windows Server 2008 that is also available on
Windows Vista. It retains the familiar IIS 6.0 process model (application pools
and message-based process activation) and hosting features (such as rapid
failure protection, health monitoring, and recycling), but it removes the
dependency on HTTP from the activation architecture. IIS 7.0 uses WAS to
accomplish message-based activation over HTTP. Additional WCF components also
plug into WAS to provide message-based activation over the other protocols that
WCF supports, such as TCP, MSMQ, and named pipes. This allows applications that
use communication protocols to use the IIS features such as process recycling,
rapid fail protection, and the common configuration system that were only
available to HTTP-based applications.
This hosting option requires that WAS be properly
configured, but it does not require you to write any hosting code as part of
the application.
Benefits: IIS is not required, Process recycling, Idle
shutdown, Process health monitoring, Message-based activation, Works with HTTP,
TCP, named pipes, and MSMQ.
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