I need initialize some structure in wcf service class as soon as possible after start of hosting service.
Now I host it in WinForms application and there I initialize this static structure.
ServiceHost host = new...
host.Open()...
new MyServiceClient().Initialize();
But I'm sure there is better way to do this. I know now it is inelegant solution...maybe little wcf-client running as windows process? (this client should be responsible only for calling this initializing method)
You can use the constructor of the service to do whatever initialization work is required.
// The service
public class MyService : IMyService {
// Constructor
public MyService() {
// Initialize things here
}
}
If the initialization work should only be performed once, you can make the constructor static. If the things being constructed are not static, you can make the service a singleton, depending on your performance needs. You can decorate the service with the following code to do that:
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
Related
I have a fairly simple design question about interaction between a self hosted WCF Service and other business classes.
Here is the WCF service contract :
/// <summary>
/// Represent requests on hardware components made by a client to the controler service
/// </summary>
[ServiceContract(CallbackContract = typeof(IHardwareServiceCallback))]
public interface IHardwareService
{
[OperationContract(IsOneWay = true)]
void OpenLeftDrawer();
[OperationContract(IsOneWay = true)]
void OpenRightDrawer();
}
The service implementation
public class HardwareService : IHardwareService
{
public void OpenLeftDrawer()
{
}
public void OpenRightDrawer()
{
}
}
A class which purpose is to handle the business logic regarding client calls on the server
class DrawerRequestManager
{
// Server side Business logic to handle OpenDrawer requests from client
}
Hosting scenario
Uri adrbase = new Uri(srvConfig.Address);
var host = new ServiceHost(typeof(HardwareService), adrbase);
host.AddServiceEndpoint(typeof(IHardwareService), srvConfig.Binding, srvConfig.Address);
host.Open();
Since this is the host that is managing the service instance lifetime, what is the proper way to handle the link between the service instance and business logic classes (DrawerRequestManager for exemple).
I'm using IOC container but i'm also interested in the response when not using IOC container.
Thanks in advance !
WCF uses parameterless constructor to create service objects, but there is a way to alter that. You need to implement your own instance provider.
You can inject your instance provider via ServiceHostFactory: see here.
Alternatively you can inject instance provider by using custom attribute for your service: see here.
Either way gives you full control of how services instances are created. You can use IOC there or just call constructor manually passing any parameters you want (e.g. reference to DrawerRequestManager instance).
I have created WCF service in VS2015:
[ServiceContract(CallbackContract = typeof(IMyCallback))]
public interface IMyService { }
IMyCallback looks like:
[ServiceContract]
public interface IMyCallback {
[OperationContract]
Task<string> OnServerEvent(UserAppEventData evData);
I've built the server, run it, then added service reference (by right click on solution explorer).
The client object is defined as
[CallbackBehaviorAttribute(
ConcurrencyMode = ConcurrencyMode.Reentrant,
IncludeExceptionDetailInFaults = true,
UseSynchronizationContext = true,
ValidateMustUnderstand = true
)]
public class QMyClient : IMyCallback { }
Automatically generated interface implementation made method in sync manner:
public string OnServerEvent(UserAppEventData evData) { }
This code does't work (and isn't asynchronous) and hangs client at OnServerEvent.
When I changed code manuallly to
public async Task<string> OnServerEvent(UserAppEventData evData)
and have done the same in auto generated "service references\...\Reference.cs, all works fine. But I don't want to change Referenece.cs every time I'm updating Service Reference.
Is there any method to force "Update Service Reference" make TBA OperationContractAttribute on callback?
At ordinary WCF service direction everything works OK, VS generates task based operations.
By default the service reference you've added to solution doesn't have asynchronous operations, but you can enable them and decide which option you use for your async methods - task-based or old-fashion asynchronous. This option is available in Advanced settings for service reference.
If you're using a svcutil tool, it will create the task-based methods by default, however, you can change that behavior by some flags like /async or /syncOnly.
What #VMAtm suggested will work out just fine.
I think, you could also use ChannelFactory for this scenario. It is very flexible and you can then await on the service operations from client side. Additional benefit, you don't need to modify client when there are these kind of changes on service side.
Something like:
var channelFactory = new ChannelFactory<IService>(
"WSHttpBinding_IService" // endpoint name
);
IService channel = channelFactory.CreateChannel();
string result = await channel.OnServerEvent();
Console.WriteLine(result);
Please note that for this scenario, you will have to import common interface library to client side as dll because then it will need to know about contracts and data contracts.
I'm injecting a business layer into a self-hosted (InstanceContextMode=per-call) WCF service by leveraging AutoFac's ServiceHost.AddDependencyInjectionBehavior() extension (as described in the Autofac documentation)
My business layer uses components that cannot be re-created each time a new request comes in (let's say it needs a persistent database connection).
As such, when building the container I'd like to register the BL service as a Single instance, i.e.:
builder.RegisterType<BusinessLayer>()
.SingleInstance();
The business-layer injection into the WCF service is working fine; my issue is that:
Dispose() is not called on ANY services created in the container: not just the Business layer itself, but the 'persistent' services too.
I'd expect this to happen for the BL service itself. From the Autofac docs again:
If you have singleton components (registered as SingleInstance()) they will live for the life of the container. Since container lifetimes are usually the application lifetime, it means the component
won’t be disposed until the end of the application.
, but why are none of my 'child' (Autofac-registered) services (i.e the 'IPersistentService' below) disposed when the lifetime scope is -- given that I'm not explicitly making them 'SingleInstance'?
Note:: this is still the case if I manually dispose the business layer service within the lifetime scope after I close the ServiceHost
E.g. (IDisposable implementations omitted for brevity):
[ServiceContract]
public interface IMyService
{
void DoStuff();
}
public class MyService : IMyService
{
IBusinessLayer _bl;
public MyService(IBusinessLayer bl)
{
_bl = bl;
}
public void DoStuff()
{
_bl.BLDoStuff();
}
}
public interface IBusinessLayer
{
void BLDoStuff();
}
public class BusinessLayer : IBusinessLayer
{
IPersistentService _service;
public BusinessLayer(IPersistentService service)
{
_service = service;
}
public void BLDoStuff()
{
// Do something that requires a 'cached' / persistent component
_service.DoSomethingWithPersistentConnection();
}
}
public interface IPersistentService : IDisposable
{
void DoSomethingWithPersistentConnection();
}
With Autofac registrations looking something like:
builder.RegisterType<BusinessLayer>()
.SingleInstance();
builder.RegisterType<MyPersistentService>()
.As<IPersistentService>()
.OnActivated(e => e.Instance.Start());
As Steven mentioned, what you experience here is a Captive Dependency problem. In other words, a singleton (BusinessLayer, registered with .SingleInstance()) keeps a lifetime-scoped or transient dependency (MyPersistentService, registered by default as transient).
Put it this way, dependencies of singleton services will always be singletons themselves, no matter how they were registered in the container. The diagram in Mark Seeman's article that Steven linked to gives a good view of this.
I think you can achieve what you expect, but your registrations are wrong.
My business layer uses components that cannot be re-created each time a new request comes in (let's say it needs a persistent database connection).
As such, when building the container I'd like to register the BL service as a Single instance
This is where the problem is. It's the dependency of the business service that has to be registered as a singleton, not the business service itself. This means you could have Autofac create a different instance of BusinessLayer for each WCF call, but the MyPersistentService instance injected into would always be the same. Does this make sense? Your registrations would then look like:
builder
.RegisterType<BusinessLayer>()
.As<IBusinessLayer>()
.InstancePerLifetimeScope(); // a new instance per WCF call
builder
.RegisterType<MyPersistentService>()
.As<IPersistentService>()
.OnActivated(e => e.Instance.Start())
.SingleInstance(); // one same instance for the lifetime of the application
The one instance of MyPersistenService would then be disposed of only after disposing the root container (that you created by calling builder.Build()) after you close the Service Host.
I have some problems with mocking WCF services:
1) I declare a class with empty methods which only implements my service interface:
public class MyFakeService : IMyService {
...
public virtual MyResult GetResult(MyResponse response){
throw new NotImplementedException();
};
}
2) I have the MyResponse class:
public class MyResponse {
public long myField;
}
3) I create a mock of the service class and a service host to host this fake service:
myFakeService = mocks.StrictMock<MyFakeService>();
ServiceHost host = new ServiceHost(myFakeService);
(here I have ommited the endpoint configuration etc.)
4) And now I try to test my client. The client.GetSomethingFromService() method exactly calls the GetResult(MyResponse) method of the service.
With.Mocks(mocks)
.Expecting(() => Expect
.Call(myFakeService.GetResult(null))
.IgnoreArguments()
.Constraints(PublicField.Value("myField", 777))
.Return(new MyResult()))
.Verify(() => myClient.GetSomethingFromService());
The issue is that if something wrong in the service, I can only see something like this:
System.ServiceModel.CommunicationObjectFaultedException:
The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used
for communication because it is in the Faulted state.
How do I know what exactly wrong? Maybe arguments constraints verification failed or something else...?
Thanks.
Firstly, avoid using strict mocks. They're a bad practice because they make your tests too brittle.
Secondly if you're testing a WCF service you don't need to spin up a ServiceHost since you'll then be doing an integration test. You're just wanting to test the logic of your service, not the WCF infrastructure.
For a run through of how to use RhinoMocks and WCF services have a look at my blog post on unit testing WCF services
I have the following WCF code:
ServiceHost host = null;
if (host == null)
host = new ServiceHost(typeof(RadisService));
How can i get a pointer to my RadisService, to make calls with it?
Well it was really for testing purposes, but please allow me to ask the question anyway, for educational purposes. What happens if my service is running on a machine (using a GUI host), several clients from different remote machines connect to the service and through the GUI leave comments on my service.
The code on my service looks like this:
public class MyClass
{
[DataMember]
static Dictionary<String, Variable> m_Variables = new
Dictionary<String, Variable>();
....
}
[ServiceContract]
public interface IMyClassService
{
[OperationContract]
bool AddVariable(String name, Variable value);
[OperationContract]
bool RemoveVariable(String name);
[OperationContract]
bool GetVariable(string name, Variable variable);
[OperationContract] List<String> GetVariableDetails();
...
}
So from my service host GUI i would like to be able to access GetVariableDetails(), and preview all the comments added from all the different clients at this point. How would i achieve this?
If you make your service a singleton you can create an instance of the service and give it to the ServiceHost:
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class CalculatorService: ICalculatorService
{
....
CalculatorService service = new CalculatorService();
ServiceHost serviceHost = new ServiceHost(service, baseAddress);
You cannot. The ServiceHost will host 1-n service class instances to handle incoming requests, but those are typically "per-call", e.g. a service class instance is created when a new request comes in, a method is called on the service class, and then it's disposed again.
So the ServiceHost doesn't really have any "service" class instance at hand that it can use and call methods on.
What exactly are you trying to achieve?
Update: the service host should really not do anything besides hosting the service - it should definitely not be calling into the service itself.
What you're trying to achieve is some kind of an administrative console - a GUI showing the current comments in your system. Do this either via a direct database query, or then just have a GUI console to call into your service and get those entries - but don't put that burden on the ServiceHost - that's the wrong place to put this functionality.