11.6 The worker

Shopfront.Worker/Program.cs:

using Shopfront;
using Shopfront.Extensions;
using Shopfront.Staff;
using Trax.Api.Auth;
using Trax.Effect.Data.Extensions;
using Trax.Effect.Data.Postgres.Extensions;
using Trax.Effect.Extensions;
using Trax.Effect.JunctionProvider.Logging.Extensions;
using Trax.Effect.Provider.Parameter.Extensions;
using Trax.Mediator.Extensions;
using Trax.Scheduler.Extensions;
 
var builder = WebApplication.CreateBuilder(args);
 
var connectionString =
    builder.Configuration.GetConnectionString("Shopfront")
    ?? throw new InvalidOperationException("ConnectionStrings:Shopfront is not set.");
 
builder.Services.AddShopfront(connectionString);
// The trains ask who the caller is. On the worker nobody is, and that is the answer they get.
builder.Services.AddTraxPrincipalAccessor();
 
builder.Services.AddTrax(trax =>
    trax.AddEffects(effects =>
            effects
                .UsePostgres(connectionString)
                .SaveTrainParameters()
                .AddJunctionLogger(serializeJunctionData: true)
                .AddDecisionRecording()
                .AddJunctionEvents()
                .AddLifecycleHook<StaffFailureHook>()
        )
        .AddMediator(mediator =>
            mediator
                .ScanAssemblies(typeof(ManifestNames).Assembly)
                // The hub authorized every job this worker runs before it was queued.
                .AllowMissingAuthorizationService()
        )
);
builder.Services.AddTraxWorker(worker => worker.WorkerCount = 2);
 
var app = builder.Build();
await app.RunAsync();

AddShopfront is the same call the hub makes. When a process starts, Trax checks the chain of every train it registered, including the ones it never runs, so every process that registers the library's trains registers their services too.
AddTraxPrincipalAccessor gives the trains a way to ask who the caller is. The hub gets it from its JWT sign-in; the worker has none, and the answer on the worker is nobody.
AllowMissingAuthorizationService says this process enforces no [TraxAuthorize]. Without it the worker refuses to start, because the library holds PlaceOrder, which declares one, and nothing here would check it. That is safe only because nothing reaches the worker but the jobs the hub queued, after the hub checked who queued them.
AddTraxWorker claims queued jobs from Postgres and runs them, two at a time. That is the cap: at most two fulfilments, or restocks, or any mix, run at once on this worker.

The worker reads the same configuration as the hub.

Shopfront.Worker/appsettings.json:

{
  "ConnectionStrings": {
    "Shopfront": "Host=localhost;Database=shopfront;Username=postgres;Password=shopfront"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  }
}

SDK Reference

AddTraxWorker | ITrainExecutionService | Queued work | Job submission | Structuring your application | Host tracking

Next: 11.7 Run both