WCF ChannelFactory and channels - caching, reusing, closing and recovery

Question

I have the following planned architecture for my WCF client library:

• using ChannelFactory instead of svcutil generated proxies because I need more control and also

Answer 1

I guess better late then never... and looks like author has it working, this might help future WCF users.

1) ChannelFactory arranges the channel which includes all behaviors for the channel. Creating the channel via CreateChannel method "activates" the channel. Channel factories can be cached.

2) You shape the channel factory with bindings and behaviors. This shape is shared with everyone who creates this channel. As you noted in your comment you can attach message inspectors but more common case is to use Header to send custom state information to the service. You can attach headers via OperationContext.Current

using (var op = new OperationContextScope((IContextChannel)proxy))
{
    var header = new MessageHeader("Some State");
    var hout = header.GetUntypedHeader("message", "urn:someNamespace");
    OperationContext.Current.OutgoingMessageHeaders.Add(hout);
}

3) This is my general way of disposing the client channel and factory (this method is part of my ProxyBase class)

public virtual void Dispose()
{
    CloseChannel();
    CloseFactory();
}

protected void CloseChannel()
{
    if (((IChannel)_client).State == CommunicationState.Opened)
    {
        try
        {
            ((IChannel)_client).Close();
        }
        catch (TimeoutException /* timeout */)
        {
            // Handle the timeout exception
            ((IChannel)innerChannel).Abort();
        }
        catch (CommunicationException /* communicationException */)
        {
            // Handle the communication exception
            ((IChannel)_client).Abort();
        }
    }
}

protected void CloseFactory()
{
    if (Factory.State == CommunicationState.Opened)
    {
        try
        {
            Factory.Close();
        }
        catch (TimeoutException /* timeout */)
        {
            // Handle the timeout exception
            Factory.Abort();
        }
        catch (CommunicationException /* communicationException */)
        {
            // Handle the communication exception
            Factory.Abort();
        }
    }
}

4) WCF will fault the channel not the factory. You can implement a re-connect logic but that would require that you create and derive your clients from some custom ProxyBase e.g.

protected I Channel
{
    get
    {
        lock (_channelLock)
        {
            if (! object.Equals(innerChannel, default(I)))
            {
                ICommunicationObject channelObject = innerChannel as ICommunicationObject;
                if ((channelObject.State == CommunicationState.Faulted) || (channelObject.State == CommunicationState.Closed))
                {
                    // Channel is faulted or closing for some reason, attempt to recreate channel
                    innerChannel = default(I);
                }
            }

            if (object.Equals(innerChannel, default(I)))
            {
                Debug.Assert(Factory != null);
                innerChannel = Factory.CreateChannel();
                ((ICommunicationObject)innerChannel).Faulted += new EventHandler(Channel_Faulted);
            }
        }

        return innerChannel;
    }
}

5) Do not re-use channels. Open, do something, close is the normal usage pattern.

6) Create common proxy base class and derive all your clients from it. This can be helpful, like re-connecting, using pre-invoke/post invoke logic, consuming events from factory (e.g. Faulted, Opening)

7) Create your own CustomChannelFactory this gives you further control how factory behaves e.g. Set default timeouts, enforce various binding settings (MaxMessageSizes) etc.

public static void SetTimeouts(Binding binding, TimeSpan? timeout = null, TimeSpan? debugTimeout = null)
        {
            if (timeout == null)
            {
                timeout = new TimeSpan(0, 0, 1, 0);
            }
            if (debugTimeout == null)
            {
                debugTimeout = new TimeSpan(0, 0, 10, 0);
            }
            if (Debugger.IsAttached)
            {
                binding.ReceiveTimeout = debugTimeout.Value;
                binding.SendTimeout = debugTimeout.Value;
            }
            else
            {
                binding.ReceiveTimeout = timeout.Value;
                binding.SendTimeout = timeout.Value;
            }
        }