What is Throttling in WCF?

WCF throttling provides properties that you can use to limit how many instances or sessions are created at the application level.

Throttling is a behavior which has three attributes:-

1. maxConcurrentCalls :- limits total no of calls that currently be in progress across  all   service instance.Default value of maxConcurrentCalls is 16.

2. maxConcurrentInstances :-  limits the number of instanceContext objects that execute at one time across a serviceHost. Default value is Int32.Max i.e. 2147483647.

3. maxConcurrentSessions :- limits the no of sessions a serviceHost Object can accept. Default value is 10.

Throttling properties can be configured either in config file or programmatically.

Configuration File:-

<behaviors>

<serviceBehaviors>

<behavior name="ServiceBehavior">

<!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->

<serviceMetadata httpGetEnabled="true"/>

<!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->

<serviceDebug includeExceptionDetailInFaults="true"/>

<serviceThrottling

maxConcurrentCalls="10"

maxConcurrentInstances="100"

maxConcurrentSessions="10"/>

        

</behavior>

</serviceBehaviors>

</behaviors>

Programmatically:-

ServiceHost host = new ServiceHost(typeof(MyService));

           ServiceThrottlingBehavior throttle

 = host.Description.Behaviors.Find();

            if (throttle == null)

            {

                throttle = new ServiceThrottlingBehavior();

                throttle.MaxConcurrentCalls = 100;

                throttle.MaxConcurrentSessions = 20;

                throttle.MaxConcurrentInstances = 100;

                host.Description.Behaviors.Add(throttle);

            }

            host.Open();