Migrate enterprise web application

[AlleSchonWeg]

Hi,
we have an old web application(client) which communicate via .Net Remoting to a windows service application(server) via tcp. The web app and the service are build with .Net Framework 4.8. The app is very big and we cannot migrate at once. As one step we plan to replace .Net Remoting with ServiceModel.Grpc.
My question is, what is the best approach to create a server and a client under .Net Framework 4.8? It should be possible that we can switch to .Net 9 or 10 without refactor the whole grpc tech again.
We have around 150 MarshalByRefObject classes in the server with a lot of methods. All calls are synchronous.

Thank you

[max-ieremenko]

Hi,

.NET Remoting is deprecated; migration to something else, in your case gRPC, is a precondition for net48 to net9 migration.

Client side

Here you can still sit on net48 and concentrate on migration to gRPC only.
Grpc.Net.Client instead of .NET Remoting.

Server side

The application must host a web server in order to accept HTTP/2 requests, and it is about ASP.NET Core.
Problem: ServiceModel.Grpc.AspNetCore is not supported on net48.

Choice: migration to gRPC and .NET at the same time.
If it is manageable for you, you are lucky :).

Choice: still sit on net48 and concentrate on migration to gRPC only.
It will be a temporary/transition solution based on Grpc.Core.Server.
At first replace .NET Remoting with Grpc.Core.Server, then migrate to net9 and replace Grpc.Core.Server with ServiceModel.Grpc.AspNetCore.
Using Grpc.Core.Server on the server side and Grpc.Net.Client on the client side is OK.

Be aware that Grpc.Core.Server is in maintenance mode and will be deprecated in favor of gRPC .NET.

See Grpc.Core.DesignTime and Grpc.Core.ReflectionEmit

Contract, data marshaling

BinarySerializer is deprecated as well as ISerializable interface.

DataContractSerializer behavior is very close to BinarySerializer, may be it is a good choice for the begining.
If the client and server will be running on different .NET versions, be aware of backward compatibility issues in binary serialization.
As an example, see #354, DateTimeOffset can't be deserialized on a server with a different .net version.

See also MessagePackMarshaller, ProtobufMarshaller.

Synchronous calls

sync or async or both is your choice:

[ServiceContract]
public interface IFoo
{
   [OperationContract]
   Bar GetBar(); // blocking unary call

   [OperationContract]
   Task<Bar> GetBarAsync(); // async unary call
}

see also SyncOverAsync

[AlleSchonWeg]

Thank you for your answer.
Our plan is to run gRPC and .Net Remoting side by side. New server methods are implemented with gRPC and old methods are migrate over time. I think we will go the Grpc.Core.Server and Grpc.Net.Client way. And after all methods transfered to gRPC we can remove .Net Remoting on the server side and migrate to .Net. The client is a web forms app and we are in a process to replace aspx with a SPA web app. Before all aspx are replaced and .Net Remoting is eliminated we can't migrate the client to .Net.
Another problem is that our models have object data types and circular references. With deprecated BinaryFormatter serialization/deserialization works without problems. We need to test which serializer meets our requirements.

I already downloaded the sample projects Grpc.Core.DesignTime and Grpc.Core.ReflectionEmit but what are the advantages and disadvantages of these two options?

Thank you very much.

[AlleSchonWeg]

Today i played a bit with the DesignTime sample project. I have two questions:

1. The _server.Services.AddCalculator(...) is showing in the error list, but the project compiles.
2. Is it necessary to use the Microsoft.Extensions.Hosting or can i do something like this to start the server:

    public static async Task Main(string[] args)
    {
        var server = new Grpc.Core.Server()
        {
            Ports = { new ServerPort("localhost", 8082, ServerCredentials.Insecure) }
        };
        server.Services.AddCalculator(new Calculator());
        server.Start();
        Console.ReadKey();
        await server.ShutdownAsync();
    }

[max-ieremenko]

what are the advantages and disadvantages of these two options

Under the hood ServiceModel.Grpc does some code generation. With ReflectionEmit, it happens at runtime (IL).
The DesignTime requires a little bit more effort from you, but all the necessary code will be generated during ms-build (C#).
See client-code-generation and server-code-generation.

The _server.Services.AddCalculator(...) is showing in the error list, but the project compiles.

Usually, after building the solution and restarting IDE, the problem should disappear. Related to Roslyn Source Generators and IDE integration.

Is it necessary to use the Microsoft.Extensions.Hosting

Certainly not.

[AlleSchonWeg]

The _server.Services.AddCalculator(...) is showing in the error list, but the project compiles.

Hmm, i tried it a lot of times but it never disappear. Restart VS, clean, rebuild again, using another computer. I have VS 17.14.6 Enterprise.

Is it necessary to use the Microsoft.Extensions.Hosting

Certainly not.

It is enough to start Grpc.Core.Server? Do you have a small sample without Microsoft.Extensions.Hosting?

In my tests a observed a unexpected behaviour. I forgot to add the [OperationContract] attribute for one method (TestMethod2) in my interface:

[ServiceContract]
public interface IDemo
{
      string TestMethod2(string request); //synchron Method
      [OperationContract]
      Task<string> TestMethod2Async(string request, CancellationToken cancellationToken = default);
}

internal class Demo : IDemo
{
        public string TestMethod2(string request)
        {
            return "TestMethod2: " + request;
        }
        public Task<string> TestMethod2Async(string request, CancellationToken cancellationToken = default)
        {
            return Task.FromResult("TestMethod2Async: " + request);
        }
}

The client calls the method:

IDemo demo = clientFactory.CreateClient<IDemo>(channel);
var result = demo.TestMethod2Async("0").Result;
var result2 = demo.TestMethod2("1");

I had expect that the call demo.TestMethod2 failed but it calls TestMethod2Async on the server.

We have a lot of methods with out parameter and my tests with out parameter failed. Is it possible to support out parameter?

Thank you again

[max-ieremenko]

The _server.Services.AddCalculator(...) is showing in the error list, but the project compiles.

need to double-check.

Do you have a small sample without Microsoft.Extensions.Hosting?

var server = new Grpc.Core.Server
{
   Ports = { new ServerPort("localhost", 8082, ServerCredentials.Insecure) }
};

server.Services.AddCalculator(
	new Calculator(),
	options =>
	{
		// ...
	});

server.Start();

Console.ReadLine();

await server.ShutdownAsync();

I forgot to add the [OperationContract] attribute for one method (TestMethod2) in my interface:

For method declarations in your example, it is expected behavior. This is a feature Sync over async.

Is it possible to support out parameter?

As soon as it will be supported by C#.

// Error CS1988 Async methods cannot have ref, in or out parameters
static async Task TestAsync(out string value1, ref string value2) { }

[AlleSchonWeg]

Thanks for the explanation. I will try it in two weeks. I'm not at work. Holidays. 🏝️

[AlleSchonWeg]

Hi @max-ieremenko ,

i resumed testing and as always i have new questions. ;)

1. In calculator.cs you have a blocking unary Sum method:
   public Number Sum(int x, int y, int z, CancellationToken cancellationToken) => new(x + y + z);
   What is the reason to have a CancellationToken in a sync method?
2. Regarding out parameters i mean the blocking variants:

	[OperationContract]
	string OutParamtTest(string input, out string stringOut, out int intOut);

Implementing this results in an error:

`error GrpcDesignTime04: Demo: Method signature [string OutParamtTest(string, out string, out int)] is not supported.`

3. The main MessagePack maintainer has left the project (Struggles with MessagePack-CSharp v3 due to source generation AArnott/Nerdbank.MessagePack#480) and focus on Nerdbank.MessagePack. Do you have plans to add Nerdbank.MessagePack as a alternative?
4. I tried MessagePack as a serializier, but it fails with more than three method parameters.

No more compiler errors with _server.Services.AddCalculator

[max-ieremenko]

For the gRPC protocol, both calls are identical:

int Sum(int x, int y, int z, CancellationToken cancellationToken);
Task<int> SumAsync(int x, int y, int z, CancellationToken cancellationToken);

The difference will be in your application (very simplified):

int Sum
	=> HttpClient.Send
	
Task<int> SumAsync
	=> HttpClient.SendAsync

In an ideal world, the application should make Async calls and avoid blocking ones.

1. What is the reason to have a CancellationToken in a sync method?

If a server-side supports cancellation, it is worth highlighting this; additionally, the operation declaration is made for demo purposes.
What is the reason to sum 3 values on the server-side? :)

2. Regarding out parameters i mean the blocking variants:

See my explanation above. The feature will not work for Async.

3. Do you have plans to add Nerdbank.MessagePack as a alternative?

Thank you for the info. Why not? Nerdbank.MessagePack is still the release candidate; it will wait for the first release.

I tried MessagePack as a serializier, but it fails with more than three method parameters.

Did you try Examples/MessagePackMarshaller.AOT? Could you reproduce the issue based on this example? or based on Examples/MessagePackMarshaller?

[AlleSchonWeg]

Hi,

Thank you for the info. Why not? Nerdbank.MessagePack is still the release candidate; it will wait for the first release.

I tried to implement a custom marshaller with Nerdbank.MessagePack. It's working but i have to use reflection, because Nerdbank needs the [GenerateShape] attribute to mark model classes etc. as serializable. ServiceModel.Grpc wraps these classes as tuples inside ServiceModel.Grpc.Channel.Message:

To make this work without reflection i have to use the GenerateShapeFor<ServiceModel.Grpc.Channel.Message> attribute. If i understand correctly how ServiceModel.Grpc works then it generates a tuple via code generation. Like this for example: ServiceModel.Grpc.Channel.Message<System.Tuple<int, string>> Its impossible to create GenerateShapeFor for every combination:

   //[GenerateShapeFor<ServiceModel.Grpc.Channel.Message>]
   //[GenerateShapeFor<ServiceModel.Grpc.Channel.Message<Tuple<int, string>>>]
   [GenerateShapeFor<MyClass>]
   [GenerateShapeFor<TestModels>]
   [Serializable]
   partial class Witness;

Did you try Examples/MessagePackMarshaller.AOT? Could you reproduce the issue based on this example? or based on >Examples/MessagePackMarshaller?

I tried to extend the Grpc.Core.DesignTime example and added the ServiceModel.Grpc.MessagePackMarshaller nuget.
Here is my test project. Method MultipleParameters in IDemo interface.
Grpc.Core.DesignTime.zip

I updated the demo and added a web application project. In this project type codegen is not working.

[max-ieremenko]

I tried to extend the Grpc.Core.DesignTime example and added the ServiceModel.Grpc.MessagePackMarshaller nuget.
Here is my test project. Method MultipleParameters in IDemo interface.

Follow MessagePackMarshaller.AOT example. For DesignTime, the MessagePackMarshaller should be configured. You can extend ICalculator with MultipleParameters and see how it works,

I updated the demo and added a web application project. In this project type codegen is not working.

The provided WebApplication1 is in Non-SDK-style format.
As far as I know, Roslyn Source Generators will not work with Non-SDK-style format projects.

[AlleSchonWeg]

I tried to extend the Grpc.Core.DesignTime example and added the ServiceModel.Grpc.MessagePackMarshaller nuget.
Here is my test project. Method MultipleParameters in IDemo interface.

Follow MessagePackMarshaller.AOT example. For DesignTime, the MessagePackMarshaller should be configured. You can extend ICalculator with MultipleParameters and see how it works,

Yes, the sample works. I don't know why it doesn't work in demo app. But it's not so important for me. I prefer the Nerdbank.MessagePack serializier.

I updated the demo and added a web application project. In this project type codegen is not working.

The provided WebApplication1 is in Non-SDK-style format. As far as I know, Roslyn Source Generators will not work with Non-SDK-style format projects.

I know that it not SDK Style. But i didn't know that Source Generators will not work with Non-SDK-styleprojects. Web Forms are not compatible with SDK-style project. I added a new class library (.NetStandard 2.0) to my solution and referenced it in the web forms project. This works.

It would be very nice, if you can take a look to integrate Nerdbank.MessagePack. I know it's only a RC version. The challenge is to make this working without reflection.

Thank you very much!