Tutorial

11.5 The hub

Shopfront.Hub/Program.cs:

using Shopfront;
using Shopfront.Auth;
using Shopfront.Data;
using Shopfront.Extensions;
using Shopfront.Staff;
using Shopfront.Suppliers;
using Shopfront.Trains.LowStockCheck;
using Shopfront.Trains.Restock;
using Shopfront.Trains.StockReport;
using Trax.Api.Auth.Jwt;
using Trax.Api.Dashboard.Extensions;
using Trax.Api.GraphQL.Extensions;
using Trax.Effect.Data.Extensions;
using Trax.Effect.Data.Postgres.Extensions;
using Trax.Effect.Data.Services.DomainContext;
using Trax.Effect.Enums;
using Trax.Effect.Extensions;
using Trax.Effect.JunctionProvider.Logging.Extensions;
using Trax.Effect.Models.Manifest;
using Trax.Effect.Provider.Parameter.Extensions;
using Trax.Mediator.Extensions;
using Trax.Scheduler.Extensions;
using Trax.Scheduler.Services.JobSubmitter;
using Trax.Scheduler.Services.Scheduling;
 
var builder = WebApplication.CreateBuilder(args);
 
var connectionString =
    builder.Configuration.GetConnectionString("Shopfront")
    ?? throw new InvalidOperationException("ConnectionStrings:Shopfront is not set.");
var development = builder.Environment.IsDevelopment();
 
builder.Services.AddShopfront(connectionString);
 
if (development)
    builder.Services.AddTraxJwtAuth(jwt =>
        jwt.UseSymmetricKey(DevJwt.Issuer, DevJwt.Audience, DevJwt.Key)
    );
else
    builder.Services.AddTraxJwtAuth(
        builder.Configuration["Auth:Authority"]
            ?? throw new InvalidOperationException("Auth:Authority is not set."),
        builder.Configuration["Auth:Audience"]
            ?? throw new InvalidOperationException("Auth:Audience is not set.")
    );
builder.Services.AddAuthorization();
 
builder.Services.AddTrax(trax =>
    trax.AddEffects(effects =>
            effects
                .UsePostgres(connectionString)
                .SaveTrainParameters()
                .AddJunctionLogger(serializeJunctionData: true)
                .AddDecisionRecording()
                .AddJunctionEvents()
                .AddLifecycleHook<StaffFailureHook>()
        )
        .AddMediator(typeof(ManifestNames).Assembly)
        .AddScheduler(scheduler =>
        {
            // The hub hands every job to the worker through Postgres and runs none itself.
            scheduler.OverrideSubmitter(services =>
                services.AddScoped<IJobSubmitter, PostgresJobSubmitter>()
            );
 
            // In Development, retries come seconds apart, and a run whose worker died is given up
            // on after a minute rather than an hour, to be watched.
            if (development)
                scheduler
                    .DefaultRetryDelay(TimeSpan.FromSeconds(5))
                    .MaxRetryDelay(TimeSpan.FromSeconds(30))
                    .DefaultJobTimeout(TimeSpan.FromSeconds(30))
                    .StaleInProgressTimeout(TimeSpan.FromMinutes(1));
 
            return scheduler
                .Schedule<IStockReportTrain>(
                    ManifestNames.StockReport,
                    new StockReportInput(),
                    Cron.Daily(hour: 2),
                    options =>
                        options
                            // The shop's holidays: no count, and none the morning after.
                            .Exclude(
                                Exclude.Dates(new DateOnly(2026, 12, 25), new DateOnly(2027, 1, 1))
                            )
                            .OnMisfire(MisfirePolicy.DoNothing)
                            .Variance(TimeSpan.FromMinutes(10))
                )
                .ThenInclude<ILowStockCheckTrain>(
                    ManifestNames.LowStockCheck,
                    new LowStockCheckInput { Threshold = 3 }
                )
                .Schedule<IRestockTrain>(
                    ManifestNames.Restock,
                    new RestockInput { Threshold = 3 },
                    development ? Every.Minutes(1) : Every.Hours(1),
                    options => options.MaxRetries(2)
                );
        })
);
builder.Services.AddTraxGraphQL(graphql =>
    graphql
        .AddDbContext<ShopfrontDbContext>()
        .ExposeOperationQueries()
        .ExposeOperationMutations()
        .GateOperations(roles: Roles.Staff)
);
 
var app = builder.Build();
 
await app.Services.EnsureSchemaCreatedAsync<ShopfrontDbContext>();
 
app.UseAuthentication();
app.UseAuthorization();
app.UseTraxGraphQL();
app.UseTraxApiDashboard(dashboard => dashboard.AllowAnonymousShell());
 
if (development)
{
    app.MapGet(
            "/dev/token/{user}",
            (string user, bool staff = false) =>
                DevJwt.Mint(user, staff ? Roles.Staff : Roles.Customer)
        )
        .AllowAnonymous();
 
    // Takes this process's fake supplier down, or brings it back.
    app.MapPost(
            "/dev/supplier/{state}",
            (string state, FakeSupplier supplier) =>
            {
                supplier.IsDown = state == "down";
                return Results.NoContent();
            }
        )
        .AllowAnonymous();
}
 
await app.RunAsync();

Three things changed:

  • AddMediator(typeof(ManifestNames).Assembly) names the library. The trains are not in the hub's assembly any more, and a train in an assembly the mediator does not scan is not registered.
  • OverrideSubmitter(... PostgresJobSubmitter ...) is what makes the hub stop running jobs. A scheduler on Postgres runs its own workers by default; naming the submitter hands every job to the background_job table instead, for a worker to claim. The hub still runs PlaceOrder, which a customer waits on, itself.
  • DefaultJobTimeout and StaleInProgressTimeout are shortened in Development. They come back below.

SDK Reference

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


Next: 11.6 The worker