Introduction: Instance management in WCF.
Instance Management: Many times we would like
to control the way WCF service objects
which are instantiated on WCF server.
Sometimes, we would like to control how long the
WCF instances should be residing on
the server.
Why we need Instance Management
We need Instance Management because there are too much difference in
applications for their needs of scalability, performance, throughput,
transactions and queued calls.
There are 3 ways by
which we can manage WCF service instance creation.
- Per-Call
- Per-Session
- Single
Per-Call instance mode
When we configure WCF service as per call, new
service instances are created for every method call you make via WCF proxy
client.
• WCF client makes first method call (method call 1).
• New WCF service instance is created on the server for this method call.
• WCF service serves the request and sends response and the WCF instance is
destroyed and given to garbage collector for clean up.
Per call instance mode is shown in figure below:
![Per call instance mode]()
Per session instance mode
Many times we would like to maintain state between
method calls or for a particular session. For this purpose, we will need to
configure the service as per session. In per session, only one instance of WCF
service object is created for a session interaction.
• Client creates the proxy of WCF service and makes method calls.
• One WCF service instance is created which serves the method response.
• Client makes one more method call in the same session.
• The same WCF service instance serves the method call.
• When client finishes his activity the WCF instance is destroyed and served to
garbage collector for clean up.
Single instance mode
Many times we would like to create one global WCF instance
for all WCF clients. To create one single instance of WCF service we need to
configure the WCF service as ‘Single' instance mode.
• WCF client1 requests a method call on WCF service.
• WCF service instance is created and the request is served. WCF service
instance is not destroyed the service instance is persisted to server other
requests.
• Now let's say some other WCF client i.e. client2 requests a method call on WCF
Service.
• Again, The same WCF instance which was created by WCF client1 is used to serve
the request of WCF client2.
Single instance mode is shown in figure below:
![Single instance mode]()