Service Discovery Endpoint Not Resolving from Client Side Code #3818

NapalmCodes · 2024-04-18T14:47:02Z

NapalmCodes
Apr 18, 2024

Probably expected, but while attempting to write a demo application for Aspire that utilizes SignalR, I have discovered using the service discovery endpoint in a web application (client side code) for an api service hosting the hub that it is unable to connect to the hub. The address http://apiservice/myHub I am going to guess is only resolvable within the orchestrator as the localhost address to the api service works fine. This is all well and good until we have multiple replicas of the api service running locally and want to "load balance" across the replicas. I implemented the extension method from @davidfowl found here for a different project in my solution (sends the message to the hub) with success but obviously that is in orchestrator and does not help with the JS client library.

I get CORS errors utilizing the http://apiservice/myHub address in chrome so I enabled those features on the API for allowing all origins to no success. Again, I realize this is probably a "bad error" if the intent is not to use the service discovery URLs locally. However, I do get a response from this URL locally which surprised me a bit (albeit not very useful):

<html><head><title></title><meta name="revised" content="1.1.7" /></head><body></body></html>

I could probably use the C# client on server and have a pass through hub to the client, but this feels a bit heavy handed. Another choice maybe is yarp or something else to reverse proxy traffic to all the replicas.

I am just curious what the recommendation from the team might be on this.

Here is my client side code currently (nothing fancy, straight from MS Learn):

"use strict";

let connection = new signalR.HubConnectionBuilder().withUrl("http://apiservice/myHub", { withCredentials: false }).build();

connection.on("ReceiveMessage", function (msg) {
    console.log(JSON.stringify(msg));
});

connection.start().then(function () {
    console.log("Connection started");
}).catch(function (err) {
    return console.error(err.toString());
});

Server side (apiservice):

using System.Text;
using System.Text.Json;
using Microsoft.AspNetCore.Mvc;

var builder = WebApplication.CreateBuilder(args);

// Add service defaults & Aspire components.
builder.AddServiceDefaults();

builder.Services.AddSignalR(o =>
{
    o.EnableDetailedErrors = true;
});

// Add services to the container.
builder.Services.AddProblemDetails();

builder.Services.AddCors(options =>
{
    options.AddDefaultPolicy(
        cpBuilder =>
        {
            cpBuilder.AllowAnyOrigin()
                .AllowAnyHeader()
                .AllowAnyMethod();
        });
});

var app = builder.Build();

app.UseCors();

// Configure the HTTP request pipeline.
app.UseExceptionHandler();

app.MapDefaultEndpoints();
app.MapHub<NotificationHub>("/myHub")
    .RequireCors();

app.Run();

Answered by svause-stryker

Apr 25, 2024

Turns out using dotnet run works as expected. I am going to guess this is a rider plugin issue.

View full answer

davidfowl · 2024-04-18T15:52:40Z

davidfowl
Apr 18, 2024
Collaborator

Yes, this is expected. Service discovery only works when HTTP client is resolving the address.

Do you have 2 different processes?

19 replies

svause-stryker Apr 22, 2024

Maybe? I am definitely on preview 5. I am guessing preview 6 isn't available for public installation yet? I am happy to try it when I can install it.

davidfowl Apr 22, 2024
Collaborator

Wait a day 😄

svause-stryker Apr 25, 2024

Got around to trying preview 6. No such luck same behavior. Is it possible the issue is MacOS specific? I am using Rider with the Aspire plugin:

svause-stryker Apr 25, 2024

Turns out using dotnet run works as expected. I am going to guess this is a rider plugin issue.

Answer selected by NapalmCodes

davidfowl Apr 26, 2024
Collaborator

Make sure you file an issue

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