Refactor client factory channel and interceptor lifetime

[JamesNK]

Fixes #1264
Fixes #842
Fixes #1044

Client factory currently recreates the channel for every client instance that is created. This wasn't ideal, but all the heavy state for in a channel was in the HttpHandler, which was cached.

Features added in the last year mean channel now has state. Retries keep track of failed calls for throttling, and load balancing opens its own sockets. Recreating channel for each client instance is no longer an option.

This PR:

• Changes the client factory to have a singleton channel for each configured client. That means multiple instances of the client will use the same channel.
• Updates interceptors to no longer always be singletons. There is now an InterceptorLifetime setting. By default, interceptors have a channel lifetime, so will be created once for a channel. But configuring an interceptor to have a client lifetime means it will get resolved per-client instance.

[captainsafia]

Nit: document this has a Channel lifetime by default?

[JamesNK]

Good idea.

I kind of want to rename InterceptorLifetime. It's more like a resolution scope. Someone could still register an interceptor as a singleton in DI and have a per-client interceptor be shared because it is a singleton in DI.

[captainsafia]

Is there a universe where we need to support a mix of interceptors registered on the obsolete Interceptors list and the new InterceptorRegistrations list?

[JamesNK]

No. The only way the old Interceptors collection could have interceptors is if someone manually added them (i.e. didn't use the interceptor extension methods).

This is for backward compatibility until the old collection gets removed.

[rizi]

@JamesNK when will a version with this merge wil be available?

And is there a way to use the this approach to set the interceptor NOT as singleton?

 .ConfigureChannel(o =>
    {
        var credentials = CallCredentials.FromInterceptor((context, metadata) =>...
}

Here is the complete sample of the approach using CallCredentials.FromInterceptor: :#1430

br

[JamesNK]

@JamesNK when will a version with this merge wil be available?

You can probably get it form the nightly feed now: https://github.com/grpc/grpc-dotnet#grpc-nuget-feed

Your link to the sample didn't work. Can you re-link it?

[rizi]

@JamesNK when will a version with this merge wil be available?

You can probably get it form the nightly feed now: https://github.com/grpc/grpc-dotnet#grpc-nuget-feed

Your link to the sample didn't work. Can you re-link it?

Sorry, here is the correct link:
https://docs.microsoft.com/en-us/aspnet/core/grpc/authn-and-authz?view=aspnetcore-5.0#bearer-token-authentication

[JamesNK]

The sample below will always create a single instance because the interceptor is being configured as the channel credentials:

services
    .AddGrpcClient<Greeter.GreeterClient>(o =>
    {
        o.Address = new Uri("https://localhost:5001");
    })
    .ConfigureChannel(o =>
    {
        var credentials = CallCredentials.FromInterceptor((context, metadata) =>
        {
            if (!string.IsNullOrEmpty(_token))
            {
                metadata.Add("Authorization", $"Bearer {_token}");
            }
            return Task.CompletedTask;
        });

        o.Credentials = ChannelCredentials.Create(new SslCredentials(), credentials);
    });

What do you want the lifetime of an interceptor to be?
Why do you want to have that lifetime?
Can you share the source code of what the interceptor would look like?

[rizi]

The sample below will always create a single instance because the interceptor is being configured as the channel credentials:

services
    .AddGrpcClient<Greeter.GreeterClient>(o =>
    {
        o.Address = new Uri("https://localhost:5001");
    })
    .ConfigureChannel(o =>
    {
        var credentials = CallCredentials.FromInterceptor((context, metadata) =>
        {
            if (!string.IsNullOrEmpty(_token))
            {
                metadata.Add("Authorization", $"Bearer {_token}");
            }
            return Task.CompletedTask;
        });

        o.Credentials = ChannelCredentials.Create(new SslCredentials(), credentials);
    });

What do you want the lifetime of an interceptor to be? Why do you want to have that lifetime? Can you share the source code of what the interceptor would look like?

I know that sample above creates a "singleton", but I want the interceptor to be resolved from the DI before every call, here is my issue I created a year ago, it's marked as fixed with your merge/pull request:
#842

[JamesNK]

A new interceptor will never be resolved before every call. But an interceptor that is registered with InterceptorScope.Client will be resolved every time a new client is created.

[rizi]

A new interceptor will never be resolved before every call. But an interceptor that is registered with will be resolved every time a new client is created.

That would be fine as long as the channel stays the same/it's not created each time a new client is created.

We have to provide/add a token for every call and this token changes from customer to customer. At the the moment we create a new client and a new channel for each request because we need the interceptor to be created as well because the interceptor gets a special info from the IOC so he can create the correct token and therefore this information must be received by the current IOC container/child container.

The problem is that always creating a new channel is quite expensive/the first call to the grpc service is quite slow. When we create the channel once all subsequent grpc service calls are quite fast. But we can't use this approach because we can't calculate the correct token.

Could you provide some more info how the InterceptorScope.Client scope can be configured? And will it be resolved using the current IOC/child container?

[JamesNK]

Unit test example here:

https://github.com/JamesNK/grpc-dotnet/blob/4dd048f1cb3160751cae2e8b171201027e4e6a70/test/Grpc.Net.ClientFactory.Tests/GrpcHttpClientBuilderExtensionsTests.cs#L374-L420

Interceptor is registered client factory using InterceptorScope.Client. And the interceptor type is registered with DI as scoped. That means the interceptor is created once per-scope, and can be injected with types from the dependency injection scope.

[rizi]

Unit test example here:

https://github.com/JamesNK/grpc-dotnet/blob/4dd048f1cb3160751cae2e8b171201027e4e6a70/test/Grpc.Net.ClientFactory.Tests/GrpcHttpClientBuilderExtensionsTests.cs#L374-L420

Interceptor is registered client factory using InterceptorScope.Client. And the interceptor type is registered with DI as scoped. That means the interceptor is created once per-scope, and can be injected with types from the dependency injection scope.

Thx for the Infos, just to be sure, the clients will be created per scope/request?

And the interceptor will be created per scope/request?

And the channel is only created once and shared between the clients? --> that would be very important for performance reason.

Br

[JamesNK]

• A client will be created every time it is resolved from DI, just like today.
• Clients will use the same channel each time they are created, e.g. every instance of GreeterClient will share a channel, and every instance of CounterClient will share a different channel.
• Interceptors can be configured to be resolved once for the channel (like today) or to be resolved each time a client is created using the current DI scope.

[rizi]

• A client will be created every time it is resolved from DI, just like today.
• Clients will use the same channel each time they are created, e.g. every instance of GreeterClient will share a channel, and every instance of CounterClient will share a different channel.
• Interceptors can be configured to be resolved once for the channel (like today) or to be resolved each time a client is created using the current DI scope.

Thx for your patience, I think that's exactly what I need.

One last question:
That means a channel for e.g GreeterClient is exactly created once, correct?

[JamesNK]

Created once per client type. If your app has GreeterClient and CounterClient then a maximum of two will be created.

Although I might change that so a single channel is created for both if no channel settings are changed. I'll need to think about that.

[amsga89]

builder.Services
.AddGrpcClient<Greeter.GreeterClient>(o =>
{
o.Address = new Uri("https://localhost:5001");
})
.AddInterceptor(InterceptorScope.Client);