# 15.4 The hub serves the storefront

Three things change in the hub. It registers the storefront's documents, it lets the storefront's
origin call it, and it can write its client manifest.

`Shopfront.Hub/Program.cs`:

```csharp compile=app file=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.Api.GraphQL.PersistedOperations.Extensions;
using Trax.Effect.Configuration.ClientExport;
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.JunctionProvider.Progress.Extensions;
using Trax.Effect.Models.Manifest;
using Trax.Effect.Provider.Parameter.Extensions;
using Trax.StateMachine.Persistence;
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();

// The storefront is served from another origin, which the browser asks the hub to allow.
builder.Services.AddCors(cors =>
    cors.AddDefaultPolicy(policy =>
        policy
            .WithOrigins(
                builder.Configuration["Storefront:Origin"]
                    ?? throw new InvalidOperationException("Storefront:Origin is not set.")
            )
            .AllowAnyHeader()
            .AllowAnyMethod()
    )
);
builder.Services.AddScoped<ISnapshotPrincipal, TraxCallerSnapshotPrincipal>();

builder.Services.AddTrax(trax =>
    trax.AddEffects(effects =>
            effects
                .UsePostgres(connectionString)
                .SaveTrainParameters()
                .AddJunctionLogger(serializeJunctionData: true)
                .AddJunctionProgress()
                .AddDecisionRecording()
                .AddJunctionEvents()
                .AddLifecycleHook<StaffFailureHook>()
        )
        .AddStateMachines(typeof(ManifestNames).Assembly)
        .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)
        // Shadow mode: everything runs, and what would be refused is logged.
        .UsePersistedOperations(persisted =>
            persisted
                .SingleNode()
                .RequirePersisted(false)
                .LogNonPersistedRequests(true)
                // The storefront's documents, which trax client writes and the build copies here.
                .ClientDocuments(Path.Combine(AppContext.BaseDirectory, "trax.documents.json"))
        )
);

var app = builder.Build();

// An export of the client manifest opens no database.
if (!TraxClientExport.Requested)
    await app.Services.EnsureSchemaCreatedAsync<ShopfrontDbContext>();

app.UseCors();
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();
}

// Serves, or with --trax-export-client writes the client manifest and exits.
await app.RunTraxAsync(args);
```

What changed:

- **`ClientDocuments(...)`** registers the documents in `trax.documents.json` at start. The file is
  read from beside the hub's build, where the project copies it.
- **`AddCors` and `UseCors()`.** The page is served from `http://localhost:5173` and calls the hub
  on `http://localhost:5080`, so the browser asks the hub first whether that origin may call it.
  The origin is configuration, so a deployed storefront names its own. The socket checks the same
  list: a WebSocket from an origin the policy does not name is refused.
- **`RunTraxAsync(args)`** in place of `RunAsync()`. Started with `--trax-export-client <path>`, the
  hub runs its startup checks, writes the manifest to the path and exits. Otherwise it serves, as
  before.
- **`TraxClientExport.Requested`** says whether this start is an export. An export opens no
  database, so the schema is not created during one.

`Shopfront.Hub/Shopfront.Hub.csproj`:

```xml file=Shopfront.Hub/Shopfront.Hub.csproj
<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
    <RootNamespace>Shopfront</RootNamespace>
  </PropertyGroup>

  <ItemGroup>
    <!-- The host tests start the hub. -->
    <InternalsVisibleTo Include="Shopfront.Tests" />
  </ItemGroup>

  <ItemGroup>
    <!-- The storefront's documents, registered at start. trax client writes the file. -->
    <None
      Include="..\web\src\trax\trax.documents.json"
      Link="trax.documents.json"
      CopyToOutputDirectory="PreserveNewest"
      Condition="Exists('..\web\src\trax\trax.documents.json')"
    />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\Shopfront.Core\Shopfront.Core.csproj" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Trax.Api.Auth.Jwt" />
    <PackageReference Include="Trax.Api.Dashboard" />
    <PackageReference Include="Trax.Api.GraphQL" />
    <PackageReference Include="Trax.Api.GraphQL.PersistedOperations" />
    <PackageReference Include="Trax.Effect.JunctionProvider.Logging" />
    <PackageReference Include="Trax.Effect.JunctionProvider.Progress" />
    <PackageReference Include="Trax.Effect.Provider.Parameter" />
    <PackageReference Include="Trax.Scheduler" />
  </ItemGroup>
</Project>
```

`Shopfront.Hub/appsettings.json`:

```json file=Shopfront.Hub/appsettings.json
{
  "ConnectionStrings": {
    "Shopfront": "Host=localhost;Database=shopfront;Username=postgres;Password=shopfront"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning",
      "Trax.Effect.JunctionProvider.Logging.Services.JunctionLoggerProvider.JunctionLoggerProvider": "Debug"
    }
  },
  "Storefront": {
    "Origin": "http://localhost:5173"
  },
  "AllowedHosts": "*"
}
```

## SDK Reference

> [Generated clients](/docs/statemachine/call-a-machine-from-typescript) | [trax client](/docs/reference/cli) | [Client manifest](/docs/sdk-reference/statemachine-api/client-manifest) | [Fetch only what a component needs](/docs/api/fetch-only-what-a-component-needs) | [Run progress](/docs/sdk-reference/graphql-api/run-progress)

---

Next: [15.5 Generate the client](/docs/book/a-generated-client/generate-the-client)