MapTraxTrainEventHub

Maps the Trax SignalR hub at a URL path. Clients connect here to receive train lifecycle events pushed by the UseSignalRHub sink.

Signature

public static HubEndpointConventionBuilder MapTraxTrainEventHub(
    this IEndpointRouteBuilder endpoints,
    string path = "/hubs/trax-events"
)

Parameter	Type	Required	Default	Description
`endpoints`	`IEndpointRouteBuilder`	Yes	N/A	Typically `WebApplication`
`path`	`string`	No	`"/hubs/trax-events"`	URL where clients open the SignalR connection

Prerequisites

The host must register SignalR services:

builder.Services.AddSignalR();

If AddSignalR() is missing, MapTraxTrainEventHub throws InvalidOperationException with guidance at startup. This fails fast before the host accepts requests rather than letting client connections fail later.

Example

var builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddSignalR();
builder.Services.AddTrax(trax =>
    trax.AddEffects(effects =>
        effects
            .UsePostgres(connStr)
            .UseBroadcaster(b => b.UseSignalRHub())));
 
var app = builder.Build();
app.MapTraxTrainEventHub();      // default "/hubs/trax-events"
// or
app.MapTraxTrainEventHub("/internal/trax-events");
app.Run();

Client examples

Blazor (C#)

@inject NavigationManager Nav
@implements IAsyncDisposable
 
@code {
    private HubConnection? _hub;
 
    protected override async Task OnInitializedAsync()
    {
        _hub = new HubConnectionBuilder()
            .WithUrl(Nav.ToAbsoluteUri("/hubs/trax-events"))
            .WithAutomaticReconnect()
            .Build();
 
        _hub.On<TraxClientEvent>("TrainEvent", async evt =>
        {
            // update component state, then re-render
            await InvokeAsync(StateHasChanged);
        });
 
        await _hub.StartAsync();
    }
 
    public async ValueTask DisposeAsync()
    {
        if (_hub is not null) await _hub.DisposeAsync();
    }
}

JavaScript / TypeScript

import { HubConnectionBuilder } from "@microsoft/signalr";
 
const connection = new HubConnectionBuilder()
    .withUrl("/hubs/trax-events")
    .withAutomaticReconnect()
    .build();
 
connection.on("TrainEvent", (evt) => {
    // evt: { metadataId, externalId, trainName, eventType, timestamp, failureReason }
});
 
await connection.start();

Payload shape

By default the hub sends a TraxClientEvent per matching lifecycle event. The shape is configurable via WithProjection. See UseSignalRHub for the field list.

SDK Reference

> UseSignalRHub | UseBroadcaster