Developers can call gRPC services from .NET Framework

[JamesNK]

Problem:

MS guidance is to migrate WCF apps to gRPC where possible when moving from .NET Framework to .NET Core. Migrating multiple inter-connected apps is a big task and is difficult to do all at once. There is a transitionary period where older .NET Framework apps will hang around and need to use newer gRPC services. There needs to be a good gRPC client solution on .NET Framework.

Our new gRPC client, Grpc.Net.Client, supports .NET Core 3 and later. .NET Framework apps must use Grpc.Core on .NET Framework. Grpc.Core is functional, but its TLS stack is problematic because it doesn't integrate with Windows cert store and breaks guidance. This blocks some customers from calling gRPC from the .NET Framework, and complicates their migration from .NET Framework to .NET Core/.NET 5.

Solution:

Grpc.Net.Client could be updated to support .NET Framework by using WinHttpHandler as its HTTP stack. WinHttp doesn't have the TLS issues that Grpc.Core does and would unblock customers.

For Grpc.Net.Client to support .NET Framework, WinHttpHandler will need to be updated to support HTTP/2 trailing headers, and to verify that it supports bidirectional streaming:

• WinHttpHandler HTTP/2 trailing headers - WinHttpHandler HTTP/2 trailing headers runtime#44778
• Add .NET Standard 2.0 support to Grpc.Net.Client - Add .NET Standard 2.0 support for Grpc.Net.Client grpc/grpc-dotnet#1176

Future:

• WinHttpHandler - HTTP/2 bidirectional streaming - WinHttpHandler - HTTP/2 bidirectional streaming runtime#44784 ... 2021/1/6 status: Not supported by WinHttp yet

[danmoseley]

Making sure this is on @karelz radar.

[danmoseley]

@karelz is discussing and working on costing.

[karelz]

@danmosemsft I will remove the Team:Libraries label, as it is now present on the one depencency. This issue should track the end-to-end User Story, which will require changes in gRPC as well (to be added above by @JamesNK I assume).

[danmoseley]

(to be added above by @JamesNK I assume).

@JamesNK are you planning to add this? We presumably need to establish that either all dependencies are committed, or none.

[JamesNK]

Added grpc/grpc-dotnet#1176. Is it ok that it is not in a dotnet repo? I can create an issue in dotnet/aspnetcore if it is a problem.

PR to support .NET standard 2.0 is already mostly done - grpc/grpc-dotnet#1118. I wanted it to verify that WinHttp changes actually work end-to-end. Interop tests show that they do 🍰

[danmoseley]

@JamesNK it's probably a good idea to make a proxy issue in aspnetcore so it shows up in themesof.net.

[JamesNK]

The grpc/grpc-dotnet issue shows up on the website.

[danmoseley]

what wizardry is this? I guess we query that repo too. Great.

[shirhatti]

@karelz @JamesNK Based on our conversation today supporting unary + server streaming calls with WinHttpHandler will happen in 6.0. As such I'm marking this as P1.