WCF service completely locked

Question

I have a WCF service configured like this:

InstanceContextMode = InstanceContextMode.PerCall,
ConcurrencyMode = ConcurrencyMode.Multiple

I have a method where I call the service about ten times per second for about 30 seconds. Randomly, the service stop to work and the client is stopped on the line where the service is called.

On the server side, I have a static object "MyStaticObject" (Not declared in my service, this is an other class on the server). This object is a Dictionnary that contains some instanced objects in which there is a backgroundworker.

I don't think there is a deadlock in the database since it lock when I try to access the service and not when I try to access the database.

I currently lock my dictionnary this way:

lock (MyClass.MyStaticLockObject)
{
    MyClass.MyStaticObject...;
}

I'd like to know what could cause this kind of weird behavior.

@Patrick: Presumably a load test. If this were part of a web service, it would be nice if one knew that it could take the punishment. — Robert Harvey, Apr 01 '11 at 19:07
@Robert I think his load test was successful... he now knows that 10 times a second for 30 seconds is more than the service can handle! > — Patrick, Apr 01 '11 at 19:09
@Robert Harvey: yes It could, but I lock this static object when I access it. @dlev: Yes, when a used object in MyStaticObject is disposed. — Jean-Philippe Leclerc, Apr 01 '11 at 19:09

Chris Wenham · Accepted Answer · 2011-04-01T19:30:54.797

I've seen WCF services lock-up under high loads if you're creating a new proxy object on the client-end for each operation. Are you sure you're not creating 10 proxy instances per second?

If you're accessing a static instance of a Dictionary, you may want to consider locking it when you do read/write operations, eg:

lock (MyStaticObject)
     MyStaticObject.Add("Foo", foo);

lock (MyStaticObject)
     foo = MyStaticObject["Foo"];

Alternatively, you could try using a thread-safe implementation of Dictionary, such as the one in this article, which uses ReaderWriterLockSlim to maintain separate locks for reading and writing.

BTW: for those incredulous that a service would be called 10 times per second, I currently work on a project where it performs quite nicely on 100 calls per second--and will have to where it gets deployed.

Thank you for your reply. I locked my MyStaticObject, please see my first post to see how I proceeded. I'm not creating a proxy every time I call the service, I open it once and it remains open until the application close. — Jean-Philippe Leclerc, Apr 01 '11 at 19:37

WCF service completely locked

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