WCF Operation Timeout Exception

Introduction

WCF client interacts with WCF host service through the following major activities:

• Address (location of the service E.g.: http:// or net.tcp://)
• Contract (Class Interface between client and server)
• Binding (Transport between client and server through encoding and Protocol)

WCF Configuration

WCF configuration should be done for both client and Server application through SVCConfigEditor.exe. The Service and client endpoint configuration should be done in both Client and Server app.config respectively. Usually for Client Server application, Binding should be done using NetTcp. This NetTcp Binding configuration should be specified in both client and server app.config bindings section of the service model. There are several timeout configurations that need to be specified in the binding such as CloseTimeout, OpenTimeout, ReceiveTimeout and SendTimeout. By default, the timeout duration is set for 1 min (00:01:00) for all these Binding Timeouts. Also, there is an InactivityTimeout configuration required for ReliableSession. The default Timeout duration for session inactivity is 10 minutes (00:10:00). These values will be picked up from the application when the client invokes the service from the service host.

Implementation of Code

Create Service Contract and Operation Contract Methods (Interface)

<ServiceContract()> _
 Public Interface IntrWCFOprContr
 <OperationContract()> _
 Function CheckForService() As Boolean
 End Interface

Interface Implementation

Public Class ClsWCFImpl
 Implements IntrWCFOprContr
 Public Function CheckForService () As Boolean _
 Implements IntrWCFOprContr.CheckForService
 'Business Logic Code/Calls goes here
 'Database calls goes here
End Function

WCF Client (VB.NET Windows Application)

'Importing WCFoperation namespace which has ClsWCFImpl
 Imports WCFOperation
Private Sub frmWCFClient_Load(ByVal eventSender As System.Object,
  ByVal eventArgs As System.EventArgs) Handles MyBase.Load
'Instantiating Channel Factory
Using serviceinvoke As New ChannelFactory(Of ClsWCFImpl)(New NetTcpBinding,
  "net.tcp://localhost:4001/ClsWCFImpl ")
Try
 Dim service As ClsWCFImpl
 service = serviceinvoke.CreateChannel()
 If serviceinvoke.State = CommunicationState.Opened Then
   If service.CheckForService() then
   'Your code goes here
   Else
     'Your code goes here
   End If
 End If
Catch ex As TimeoutException
 'System.Diagnostics.Debug.Assert(False, "")
 'Debug.Assert(False, "")
 Trace.WriteLine("An exception of type '" + ex.GetType().ToString() _
 + " occurred " _
 + ex.Message, "Exceptions")
 End Try
 End Using
 End Sub

WCF Service Host (Windows Service)

'Code in Service1.vb to create and open service host
Imports WCFOperation
Public TheHost As ServiceHost
Protected Overrides Sub OnStart(ByVal args() As String)
 Try
 If TheHost Is Nothing Then
  TheHost = New ServiceHost(GetType(ClsWCFImpl))
  TheHost.Open()
 End If
 Catch ex As CommunicationObjectFaultedException
  Trace.WriteLine("An exception of type '" + ex.GetType().ToString() _
  + "occurred while OnStart Function in WCF Service. The message of the exception is: " _
  + ex.Message, "Exceptions")
 End Try
End Sub

Protected Overrides Sub OnStop()
Try
 Trace.WriteLine("Windows Service - OnStop " & Date.Now.ToString, "Informational")
 If TheHost IsNot Nothing Then
  TheHost.Close()
 End If
 ' 03/25/2008 - Added code to log Informational messages
End Try
End Sub

How It Works

The above code represents WCF client windows application hosted in a Windows Service. The WCF client will check for host status. If the host is opened (Service running), the communication starts between the WCF client and Service host through the endpoint address mentioned. The above sample works fine with the default WCF configuration as long as there is no delay in the database calls such as Executing stored procedure, queries and filling DataTables and DataSets using Dataadapters.

Problem

The same code sample will throw an Operation Timeout Error under the following circumstances:

• If there is a delay for More than a Minute in database responses
• OLEDB/SQL/ODBC Command Execution
• Dataadapter.Fill with DataTable or DataSet
• Reading data using DataReader

The delay can happen in so many ways such as execution from Database, execution of Business logic from different layers, delay response from other interfaces referenced in the application. Because of these delays, the WCF client goes Idle from the WCF host. If the client goes Idle from the WCF service, it will throw the below error.

Error

An exception of type 'System.TimeoutException occurred while <Function Name> Function'. The message of the exception is: This request operation sent to net.tcp://localhost:4001/ ClsWCFImpl did not receive a reply within the configured timeout (00:01:00). The time allotted to this operation may have been a portion of a longer timeout. This may be because the service is still processing the operation or because the service was unable to send a reply message. Please consider increasing the operation timeout (by casting the channel/proxy to IContextChannel and setting the OperationTimeout property) and ensure that the service is able to connect to the client.

Solution

To avoid this timeout error, we need to configure the OperationTimeout property for Proxy in the WCF client code. This configuration is something new unlike other configurations such as Send Timeout, Receive Timeout, etc., which I discussed early in the article. To set this operation timeout property configuration, we have to cast our proxy to IContextChannel in WCF client application before calling the operation contract methods. Here I am repeating the same WCF client Windows application code with the Operation timeout changes highlighted in yellow:

Imports WCFOperation
Private Sub frmWCFClient_Load(ByVal eventSender As System.Object,
  ByVal eventArgs As System.EventArgs) Handles MyBase.Load
'Instantiating Channel Factory
Using serviceinvoke As New ChannelFactory(Of ClsWCFImpl)(New NetTcpBinding,
  "net.tcp://localhost:4001/ClsWCFImpl ")
Try
  Dim service As ClsWCFImpl
  service = serviceinvoke.CreateChannel()
  If serviceinvoke.State = CommunicationState.Opened Then
    'Casting the Proxy with IContextChannel and set the Operation timeout property
    'with the time duration in seconds
    DirectCast(service, IContextChannel).OperationTimeout = New TimeSpan(0, 0, 240)
    If service.CheckForService() then
      'Your code goes here
    Else
      'Your code goes here
    End If
  End If
  Catch ex As TimeoutException
  'System.Diagnostics.Debug.Assert(False, "")
  'Debug.Assert(False, "")
  Trace.WriteLine("An exception of type '" + ex.GetType().ToString() _
  + " occurred " _
  + ex.Message, "Exceptions")
End Try
End Using
End Sub

Here, timeout duration is set as 240 seconds. The duration can also be set in Hours or Minutes format based on the requirement in the application and tentative delay expected from database or from other interfaces response. It is better to keep the timeout duration in the app.config of the application and keep changing it when required.

Conclusion

This operation timeout configuration is for the service that was able to connect to the client with the specified duration. The same solution is also applicable when hosting WCF in a managed .NET application such as Console or web application (ASP.NET).

Wish you all the best !!!

History

• 31^st July, 2008: Initial post