Change Client address at runtime

[adamradocz]

Hi,

I'm using ASP.NET Core on .NET 6 framework. The client factory is configured in the DIC and the address is passed by the IOptionMonitor. When the configuration is updated I'm still getting the a client from the DIC with the old address.

How should I handle a scenario in runtime when the server address is changed?

Thanks!

[JamesNK]

Could you give a code sample of what you're doing with IOptionMonitor and the address? Are you using this approach with other configuration and updating IOptionMonitor does work?

[adamradocz]

Here's a sample code. The second client still uses the same channel even though the clientOptions contains the new address.
Do you want me to upload the sample project?

using GrpcClient.Models;
using GrpcServer;
using Microsoft.Extensions.Options;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddGrpc();
builder.Services.Configure<ClientOptions>(builder.Configuration.GetSection(nameof(ClientOptions)));

builder.Services.AddGrpcClient<Greeter.GreeterClient>((serviceProvider, factoryOptions) => 
{
    var clientOptions = serviceProvider.GetRequiredService<IOptionsMonitor<ClientOptions>>();
    factoryOptions.Address = clientOptions.CurrentValue.ServerAddress;
});


var app = builder.Build();

// Current client
var clientOptions = app.Services.GetRequiredService<IOptionsMonitor<ClientOptions>>();
app.Logger.LogInformation("Address: {Address}", clientOptions.CurrentValue.ServerAddress);
var client = app.Services.GetRequiredService<Greeter.GreeterClient>();

// Waiting to change the Uri in the appsettings.json
app.Logger.LogInformation("Waiting for 30 seconds...");
await Task.Delay(TimeSpan.FromSeconds(30));

// New client
app.Logger.LogInformation("Address: {Address}", clientOptions.CurrentValue.ServerAddress);
var newClient = app.Services.GetRequiredService<Greeter.GreeterClient>();

app.Run();

[adamradocz]

@JamesNK any news about this?

[JamesNK]

No. There aren't any plans to do this right now.

.NET features that use configuration generally use a snapshot of those settings when they start. Few support runtime changes. It would be a significant amount of work to change the gRPC client factory to support it, so we'll probably only do it if there is a lot of community interest in this feature.

For advanced scenarios like this, I suggest managing a channel and client in custom code and not using gRPC client factory.

[a-priestley]

I have an application that would benefit from this capability.

Is there no way to restart the client service when detecting a change using Options Monitor?

[mindonwarp]

Well, I just came to the issues page to post the same question and saw that one already existed. My use case would be to allow the user to set the server address via a text box in a UI, allowing them to connect to several different services know at runtime.

It looks like right now there are only two options:

1. Change the address, save it to a config file, restart the whole app,
2. Don't use the provided client factory

How unfortunate 😢 Consider this my +1 to ".. a lot of community interest in this feature."

[James2195]

We've just come across this issue too. Our use case is that the gRPC server is running in a windows service. So when the service goes down and has to restart it may not necessarily be able to reacquire the same hosting port. So we need the clients to dynamically update to point to whichever new port it's able to host on.
I've been going down the path of creating a custom client factory which creates a new channel if the address changes but it seems that since everything is marked as internal in the gRPC library I've ended up with a lot of code copied across into our repo.