gRPC apps can make resilient API calls with client retry support

[JamesNK]

Automatically retrying some failed API calls (i.e. connection failure, transient server error) is a common task in apps. Polly is an OSS library often used to support retries with RESTful APIs. Unfortunately Polly doesn't work with gRPC.

There is a gRPC specification for retrying failed calls - https://github.com/grpc/proposal/blob/master/A6-client-retries.md

The spec is implemented by the two first-class gRPC implementations: grpc-go and grpc-java. It is partially implemented by ccore and its related bindings (C++, PHP, Python, C#). There is currently no retry support in grpc-dotnet.

Reasons to do:

• To maintain feature parity with other first-class gRPC implementations
• Support apps that need retry functionality to be resilient
• First-party customer demand

Dev features/work:

• Add API to get RST_STREAM value from HTTP exceptions - Add API to get RST_STREAM value from HTTP exceptions runtime#43239
• Add support for retries to gRPC client library - Add gRPC retry support grpc/grpc-dotnet#1189
• gRPC client update to read protocol error from new .NET 6 exceptions - gRPC client update to read protocol error from new .NET 6 exceptions grpc/grpc-dotnet#1241

[terrajobst]

What epic should this be listed under?

[danmoseley]

@JamesNK any requirements on the client networking stack here?

[JamesNK]

What epic should this be listed under?

It was under cloud native. @richlander removed it. What was the reason behind that?

[JamesNK]

@JamesNK any requirements on the client networking stack here?

Maybe. I will need to do some investigation then talk to client team

[danmoseley]

OK, please let us know if there are. cc @karelz

[Pilchie]

@glennc should this be parented somewhere in the Cloud Native Theme?

[Pilchie]

This is done now, right @JamesNK ?

[JamesNK]

Done! https://docs.microsoft.com/en-us/aspnet/core/grpc/retries?view=aspnetcore-6.0

A feature wasn't added in HttpClient, which is why some issues aren't closed, but I worked around it.

[mairaw]

Bulk closing .NET 6 epics and user stories. If you think this issue was closed in error, please reopen the issue and update it accordingly.