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The future of gRPC in C# belongs to grpc-dotnet

Update 2021-05-03: The maintenance period for Grpc.Core has been extended until May 2023. See announcement for more info on the future of Grpc.Core.

TL;DR grpc-dotnet (the Grpc.Net.Client and Grpc.AspNetCore.Server nuget packages) is now the recommended gRPC implementation for .NET/C#. The original gRPC C# implementation (the Grpc.Core nuget package) will enter maintenance mode and won’t be getting any new features and will only receive important bug fixes and security fixes going forward. The ultimate plan is to phase out Grpc.Core completely at some point in the future. This announcement describes the reasons why we have decided to do so and lays out the plan in more detail.

In September 2019 we announced general availability of a new gRPC C# implementation that is no longer based on the gRPC C core native library and that’s using the HTTP/2 protocol implementation that was added in .NET Core 3 and ASP.NET Core 3. We refer to this implementation as “grpc-dotnet”.

When we were introducing the grpc-dotnet implementation, we announced that both gRPC C# implementations (the new pure C# grpc-dotnet implementation and the original gRPC C# implementation based on C core native library) would co-exist side by side, letting the users choose which implementation works best for them. That made a lot of sense since grpc-dotnet was brand new back then and required a just-released .NET Core framework, while the original gRPC C# implementation had been stable for a long time, had lots of users and worked on even very old .NET Framework versions. Things needed some time to settle.

Since then, the new grpc-dotnet implementation has come a long way: it has been adopted by many users and became very popular, it has been used by a lot of applications in production environments, and has also added a lot of interesting new features. In addition, its main prerequisite, the .NET Core 3 framework, has been around for a while now and its adoption numbers are growing.

At the same time, while the original gRPC C# implementation (often referred to as “Grpc.Core”, the name of its nuget package) definitely has its place and it is hugely popular, we are now nearing a point where some of the design decisions that made perfect sense back in 2016 (when gRPC C# was released as GA) no longer have the weight they used to. For example, we decided to base the gRPC C# implementation on a native library because in 2016, there was no usable C# HTTP/2 library that we could depend on. By depending on the C core native library instead, we were able to deliver a stable, high performance gRPC library much faster than if we had to implement everything in C# from scratch. But from today’s perspective, taking a native dependency doesn’t make that much sense anymore since HTTP/2 support is now built into the .NET Core framework. The benefits of having a native dependency are diminishing, while the maintenance burden of having one is staying the same.

Out of the two stable C# implementations, the grpc-dotnet implementation is definitely the one that has more future potential. It is a more modern implementation that is well-integrated with the modern versions of .NET and it’s likely going to be more aligned with where the C# community will be a few years from now. It is also a pure C# implementation (no native components), which makes it much more contribution friendly, leads to better debuggability and it is simply also something that C# enthusiasts like to see.

Because the maintenance costs of having two official implementations of gRPC for C# are nontrivial and because grpc-dotnet seems to be the best choice for all users in the long run, we would like to announce the intent to phase out the original gRPC C# implementation (nuget package Grpc.Core) in favor of the more modern and more forward-looking grpc-dotnet implementation.

The details of the plan are described in the following sections, along with further explanation why it makes sense. To help understand the consequences of the decision to phase out Grpc.Core, we have also come up with a list of frequently asked questions and provided answers to them.

What makes grpc-dotnet the preferred implementation

Simply said, grpc-dotnet seems to be a better bet for the future. Some of the most important points were already mentioned. Here is a more detailed list of reasons why we believe grpc-dotnet will serve the users’ needs better:

  • It’s a more modern implementation, based on features of the recent version of the .NET framework. As such, it will probably be the more viable one of the two implementations in the future.

  • It’s more aligned with where the C# / .NET community is now and in the future. Staying aligned with where the community is heading seems to be the best bet for the future of gRPC in C#.

  • The implementation is much more agile and contribution friendly - because it’s internally based on well known primitives / APIs (ASP.NET core serving APIs and HTTP2 client) and it’s implemented in pure C#, the code is much more accessible to C# developers (both to users that just want to understand how things work and to potential contributors who would author PRs). The grpc-dotnet codebase is relatively small, it takes seconds to build, running the tests is easy and quick. In the long run, easier development and contribution friendliness should make up for some of the features that are missing today and make it a superior choice for the users – that is, lowering the barrier to contribute and fix/improve stuff translates into more stuff being fixed and better user experience after some time.

  • Having a library that is implemented in pure C# is something that’s generally favored by the .NET community, compared to an implementation that depends on a native component. While C# has good support for interoperating with native libraries, it is a technique that most C# developers are not familiar with and it looks like a black box to them. Native interop is tricky to get it right and has many downsides (e.g. more complicated development and build process, complex debugging, hard to maintain, hard to get community contributions, hard to provide support for multiple platforms). With Grpc.Core we were able to overcome most of these challenges (so things work these days), but it has been a lot of effort, the solutions are sometimes complex and fragile and maintaining it is costly and requires a lot of expertise.

    NOTE: the Google.Protobuf library for C# is already written purely in C# (no native components), so having a pure C# implementation of gRPC gets rid of native components from developers’ microservice stack completely

Why not keep Grpc.Core forever?

Developing two implementations of gRPC in C# isn’t free. It costs valuable resources and we believe that the engineering time would be better spent on making gRPC in C# easier to use and on adding new features (and fixing bugs of course), rather than needing to work on two different codebases that both serve the same purpose. Also, having two separate implementations necessarily fragments the user base to some extent and splits the contributors’ efforts into two. Also just the simple act of users needing to choose which of the two implementations they want to bet on comes with uncertainty and inherent risk (none of which we want for our users).

By making grpc-dotnet the recommended implementation and by making the Grpc.Core implementation “maintenance only” (and eventually phasing it out), we are aiming to achieve the following goals:

  • Free up engineering resources to work on better features and better usability.
  • Unify the gRPC C# user base. This will lead to directing all community work and contributions toward a single implementation. It also removes the inherent friction caused by the user needing to choose which of the two official implementations to use.
  • Address some of the well known pain points of Grpc.Core that would be too difficult to address by other means.
  • Futureproof C#/.NET implementation of gRPC by staying aligned with the .NET community.

The plan

Phase 1: Grpc.Core becomes “Maintenance Only”

When: Effective immediately (May 2021)

From now on, we are no longer going to provide new features or enhancements for Grpc.Core. Important bugs and security issues will continue to be addressed in a normal way.

We will publish Grpc.Core releases normally, with the usual 6 weekly cadence.

The releases will be based on the newest grpc C core native library build, so all new features that don’t require C# specific work will also be included.

Phase 2: Grpc.Core becomes “Deprecated”

When: 1 year from now (May 2022)

Once this milestone is reached, Grpc.Core will no longer be officially supported and all the users will be strongly advised to only use grpc-dotnet from this point onwards.

The Grpc.Core nuget packages will remain available in the nuget.org repository, but no more fixes will be provided (= not even security fixes).

Future of Grpc.Tools and Grpc.Core.Api nuget packages

Both packages will continue to be fully supported, since they are strictly speaking not part of Grpc.Core and they are also used by grpc-dotnet.

  • the Grpc.Tools nuget package which provides the codegen build integration for C# projects will continue to be supported (and will potentially get improvements) – as it’s used by both Grpc.Core and grpc-dotnet. This package is independent of C core.
  • Grpc.Core.Api package is a prerequisite for grpc-dotnet so it will potentially evolve over time as well (but it’s a pure C# API only package and since it only contains the public API surface, changes are very infrequent)

Q & A

I’m a current Grpc.Core user, what does this mean for me?

While we are going to continue supporting Grpc.Core for a while (see the deprecation schedule for details), you’ll have to migrate your project to grpc-dotnet if you wish to continue getting updates and bug fixes in the future.

How do I migrate my existing project to grpc-dotnet?

Since Grpc.Core and grpc-dotnet are two distinct libraries, there are going to be some code changes necessary in your project. Since both implementations share the same API for invoking and handling RPCs (we’ve intentionally designed them to be that way), we believe that the code changes necessary should be fairly minimal. For many applications you’ll simply need to change the way you configure your gRPC channels and servers; that is usually only a small portion of your app’s implementation and tends to be separate from the business logic.

For more tips on how to migrate from Grpc.Core to grpc-dotnet, see Migrating gRPC services from C-core to ASP.NET Core.

We plan to publish a more detailed migration guide in the future to facilitate the migration from Grpc.Core to grpc-dotnet.

I’d like to use gRPC in C# for a new project. Which implementation should I choose?

We strongly recommend only using grpc-dotnet for new projects. We are going to stop supporting Grpc.Core in the future.

Does this mean I need to stop using Grpc.Core right now?

No, Grpc.Core will continue to be supported for a while (see the deprecation schedule). There should be enough time for you to assess the situation and plan your migration.

I’m not using gRPC directly in my code, but I’m using the Google Cloud Client Libraries (which do use Grpc.Core under the hood). How does this impact me?

This deprecation does not currently impact existing users of Google Cloud Client Libraries.

Since Grpc.Core is an integral part of these client libraries, security and bug fixes for Grpc.Core will continue to be provided for Google Cloud Client Libraries.

The client libraries for which the extended support will be provided:

Note that the extended support of Grpc.Core will only be provided for Grpc.Core when used as part of these client libraries. For other use cases than the Google Cloud Client Libraries, Grpc.Core won’t be officially supported past the deprecation date and users must migrate existing workloads to grpc-dotnet before the deprecation happens.

Where can I find the list of supported features?

Our documentation on github has a comparison of supported features.

I have an important Grpc.Core use case that is not covered by this document.

We welcome your feedback! Write to us through the grpc-io Google Group, or any other of the main gRPC community channels.