WCF ConcurrencyMode.Multiple

Question

I dont know how to check if im right or wrong so your help will be great.

A. From my understanding, IsOneWay=true = the client doesnt want to wait for the method to end. so the service will execute this method when he want. But, in some cases, does the service will use multi-threading to execute the method?

B. when I use ConcurrencyMode.Multiple, what is the diffrence between using IsOneWay=true & IsOneWay=false.

Answer 1

ConcurrencyMode and Messaging Pattern are not so directly related.

IsOneWay affects how Client and Server interact.

The ConcurrencyMode is a server-side issue, the Client is not aware of this setting.

Answer 2

From: http://msdn.microsoft.com/en-us/library/ms751496.aspx

HTTP is, by definition, a request/response protocol; when a request is made, a response is returned. This is true even for a one-way service operation that is exposed over HTTP. When the operation is called, the service returns an HTTP status code of 202 before the service operation has executed. This status code means that the request has been accepted for processing, but the processing has not yet been completed. The client that called the operation blocks until it receives the 202 response from the service. This can cause some unexpected behavior when multiple one-way messages are sent using a binding that is configured to use sessions. The wsHttpBinding binding used in this sample is configured to use sessions by default to establish a security context. By default, messages in a session are guaranteed to arrive in the order in which they are sent. Because of this, when the second message in a session is sent, it is not processed until the first message has been processed. The result of this is that the client does not receive the 202 response for a message until the processing of the previous message has been completed. The client therefore appears to block on each subsequent operation call. To avoid this behavior, this sample configures the runtime to dispatch messages concurrently to distinct instances for processing. The sample sets InstanceContextMode to PerCall so that each message can be processed by a different instance. ConcurrencyMode is set to Multiple to allow more than one thread to dispatch messages at a time.