WCF reliability issues - wcf

Question

Trying to test the reliability of my wcf services. I am calling a wcf service within a loop from the client side. The wcf rest service (webhttpbinding) does some data processing and inserts
records into a database. The entire operation is done within a transaction.
I find that out of about 60 messages (60 times the service being called from inside a loop) only 40 are going through to the db if I set my InstanceContextMode to PerCall. There are no errors no exceptions. The messages are just being dropped.
If I set the InstanceContextMode to Single then I see all messages getting to the db.
Is the InstanceContextMode.Percall being lossy the expected behavior? Also, I do not have concurrency set. Any clarifications would be greatly helpful. Added the code. Using MySQL as the db...
EDIT My bad - I just noticed that I get an exception on the server side - {"Deadlock found when trying to get lock; try restarting transaction"}
This is because there is another transaction invoked on the same records while a transaction is under progress. Fixing it by restarting the transaction if it fails once.
The service
[WebInvoke(UriTemplate = "employee", Method = "POST")]
public long AddNewEmployee(EmployeeEntity newEmployee)
{
EmployeeRepository eRep = new EmployeeRepository();
return eRep.AddNewEmployee(newEventEntity);
}
The repository class constructor initializes the object context
public EmployeeRepository()
{
bd = new EmployeeEntity();
}
Code - The service call
//bd is the object context
//there are two tables
internal long AddNewEmployee(EmployeeEntity newEmployee)
{
bool tSuccess = false;
using (TransactionScope transaction = new TransactionScope())
{
try
{
//get existing employees
var existingEmployees = from employee
in bd.employees select employee;
List<employee> returnedEmployees = new List<employee>();
//Do some processing
returnedEmployees = DoSomeprocessing(existingEmployees);
//Insert returned employees as updates
foreach (employee e in returnedEmployees)
{
bd.employees.AddObject(e);
}
bd.SaveChanges();
returnedEmployees.Clear();
//add to second table
bd.otherdetails.AddObject(newEmployee);
bd.SaveChanges();
//Transaction Complete
transaction.Complete();
tSuccess = true;
}
catch (Exception e)
{
//return something meaningful
return -1;
}
}
if (tSuccess)
{
//End Transaction
bd.AcceptAllChanges();
return 200;
}
else
{
return -1;
}
}
The client side just calls the service in a loop

Answer 1

I highly suggest adding global exception handling for any WCF. It has helped me save many hours of debugging and will catch any unhandled exceptions. It's a little bit more involved than global.ascx in ASP.NET
Step 1 - Implement IErroHander and IServiceBehavior
Notice inside HandleError I'm using Enterprise Library to handle the exception. You can use your custom implementation here as well.
public class ErrorHandler : IErrorHandler, IServiceBehavior
{
public bool HandleError(Exception error)
{
// Returning true indicates you performed your behavior.
return true;
}
public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
// Log Exception
ExceptionPolicy.HandleException(error, "ExceptionPolicy");
// Shield the unknown exception
FaultException faultException = new FaultException(
"Server error encountered. All details have been logged.");
MessageFault messageFault = faultException.CreateMessageFault();
fault = Message.CreateMessage(version, messageFault, faultException.Action);
}
private IErrorHandler errorHandler = null;
public ErrorHandler()
{
}
public ErrorHandler(IErrorHandler errorHandler)
{
this.errorHandler = errorHandler;
}
public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
foreach (ChannelDispatcherBase cdb in serviceHostBase.ChannelDispatchers)
{
ChannelDispatcher cd = cdb as ChannelDispatcher;
if (cd != null)
{
cd.ErrorHandlers.Add(new ErrorHandler());
}
}
}
public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters)
{
foreach (ChannelDispatcherBase cdb in serviceHostBase.ChannelDispatchers)
{
ChannelDispatcher cd = cdb as ChannelDispatcher;
if (cd != null)
{
cd.ErrorHandlers.Add(new ErrorHandler());
}
}
}
public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
}
}
}
Step 2 - Create Error Element
public class ErrorHandlerElement : BehaviorExtensionElement
{
protected override object CreateBehavior()
{
return new ErrorHandler();
}
public override Type BehaviorType
{
get
{
return typeof(ErrorHandler);
}
}
}
Step 3 - Add Element to web.config
<serviceBehaviors>
<behavior>
<ErrorHandler />
</behavior>
</serviceBehaviors>