WCF INSTANCE MANAGEMENT Dhananjay Kumar MVP-Connected Syste m

WCF INSTANCE MANAGEMENT Dhananjay Kumar

MVP-Connected System

Instance Management is a technique to decide, which SERVICE INSTANCE handles which CLIENT REQUEST and when?

This is a service side implementation detail This is useful to decide scalability,

performance, durability, transactions and queued calls

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BEHAVIOR Instance management is a service side activation

implementation detail that should not get manifested to the client. WCF achieve this by BEHAVIOR.

A Behavior is a local attribute of service that does not affect its communication patterns.

Client does not aware of the Behavior. Service does not manifest behavior in binding or

metadata. Practically Behaviors are WCF classes. These are used at the runtime operations.

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Instance ManagementBEHAVIOR

SERVICE BEHAVIOR

This applies directly to service implementation class.

This affects all the endpoints. This is used to configure service instance mode.

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OPERATION BEHAVIOR

This is used to configure operation behavior. This affects only implementation of a particular

operation. This could apply only to method that implements

contract operation. This is not applied to the contract definition itself.

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Per Call Instance ModeEvery Client request gets a new dedicated service instance. A service instance exists only when a client call is in progress.

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Per Call Instance Mode

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Per Call Instance Mode

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Per Call Instance Mode

Demo

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Per Session Instance Mode

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Per Session Instance Mode

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Per Session Instance Mode WCF can maintain a logical session between a client and service. The service instance remains in the memory throughout the

session. The client session is per service endpoint per proxy.

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Configuring Session full Service

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Behavior FacetsThe Behavior part is required, so that WCF will keep the

Service Instance Context alive throughout the session.

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Behavior Facets InstanceContextMode.PerSession is default value for InstanceContextmode

property. The session terminates when client closes the proxy. Proxy has to notify the service that session has been closed and service calls the

Dispose () method on worker thread.

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Contract FacetsIn order to create all messages from a particular client to a particular instance WCF needs to identify the client and this is done by TRANSPORT SESSION

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Contract Facets

For this ServiceContract attribute having a property called SessionMode. Type of property SessionMode is enum SessionMode. It is inside namespace System.ServiceModel. Property SessionMode is a public property.  SessionMode enum is default to SessionMode.Allowed. The Configured value of SessionMode is exposed to client in MetaData.

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Contract Facets

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SessionMode.Allowed When the SessionMode is configured with SessionMode.Allowed, transport session are allowed but not

enforced. The Behavior of service will depend upon behavior configuration and binding.

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SessionMode.Allowed

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SessionMode.Required SessionMode.Required value restricts to use Transport level session. If a contract is configured as SessionMode.Required with a service end point who's binding does not

maintain a Transport level session a Run time error will encountered at loading of service.

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SessionMode.Required

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SessionMode.Required

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SessionMode.NotAllowed This disallows the use of Transport session. Regardless of the service configuration, when SessionMode.NowAllowed is configured at contract, the service will always behave as Per-call

service.

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SessionMode.NotAllowed

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SessionMode.NotAllowed

DEMO

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Singleton Instance Mode

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Singleton Instance Mode

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Singleton Instance Mode

The Singleton Service Instance created only once. It created when the service host is created. It lives forever. It got disposed only when host shuts down. Singleton service instance does not require client to maintain any logical session. It does not required to use binding that supports transport level session.

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Singleton Instance Mode

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Singleton Instance Mode

Having scalability problem. All requests to service will run on different worker thread, so it will cause synchronization problem. Only one client could have access to singleton service instance at a time. It will decrease throughput of the service. Responsiveness is very low Singleton Service instance should only be used, when no other options are available. For instance Global Log Book, Single Communication Port etc.

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Singleton Instance Mode

DEMO

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Instance Management

Thank You.

Dhananjay KumarMVP-Connected System