wcf entry (8) - Concurrency Control

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This blog will explain how to set up concurrent service

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Concurrent (Concurrency)

Concurrency control server context instance the InstanceContextuse of threads.

There are three concurrent value can be set Single, Reentrant,Mutiple

Which, `Mutiple is multi-threaded, meaning the service instance can allow multiple threads access

SingleAnd Reentrantare single-threaded

Single

SingleSimilar to the single-threaded synchronization, during a service call will block calls to other services

We make the following example. We set up a duplex communication services operating agreement is one-way operation agreement callback request is a reply (synchronous) of. In the callback method each call a new instance, and the callback method we did three seconds of sleep, analog communication delay. This time we call continuous service many times.

Results As shown, a deadlock occurs while waiting for the callback return

Since we returned from the callback, try to access the service object. But clients are single threaded synchronous, we are waiting for the callback method returns, resulting in a deadlock.

Now we try to operate a one-way agreement callback method changed

We see that the server has the execution order

A Reentrant (reentrant)

We just say that Singlemay occur deadlock. And Reentrantjust to solve this problem.

ReentrantRefers to invoke other services (or callback) In the method, the message may allow the subsequent re-entry (re-access) object

For the example of a deadlock, we only need to adjust the concurrent modeReentrant

We saw at the end when calling the callback service to start processing a message. Sequentially perform the subsequent return code message. Like async / await mode

Mutiple

MutipleIt refers to the code allows multithreaded access.

We changed three examples of concurrencyMutiple

We can see the code output smoothly, but the order is chaos. Because multiple threads access.

summary

We studied the concurrent WCF service, its features are

• SingleMaintaining single-threaded synchronization, but may deadlock
• ReentractReentrant, the call to allow other services, similar to the async / await
• MutipleAllows multithreaded access

Reference links:

• [WCF] concurrent service in the "re-entrant mode" - Click here to see Solitude - blog Park
• ConcurrencyMode Enum (System.ServiceModel) - Microsoft Docs

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