10.4 Tell staff when scheduled work fails

A lifecycle hook runs on a run's transitions: started, completed, failed, cancelled. One that reacts to a failure is how staff hear about a scheduled run nobody was watching. It runs for every train, so it picks out the ones a manifest ran.

Staff/StaffFailureHook.cs:

using Trax.Effect.Models.Metadata;
using Trax.Effect.Services.TrainLifecycleHook;
 
namespace Shopfront.Staff;
 
// Tells staff about every failed run of scheduled work. A failed order is the customer's to see.
public class StaffFailureHook(IStaffNotifier staff) : ITrainLifecycleHook
{
    public Task OnFailed(Metadata metadata, Exception exception, CancellationToken ct) =>
        metadata.ManifestId is null
            ? Task.CompletedTask
            : staff.Notify($"{metadata.Name} failed: {exception.Message}", ct);
}

A hook's failure is logged and never fails the run it was told about.

The supplier joins the shop's services, once, so the Development switch and the train see the same one.

Extensions/ShopfrontServiceCollectionExtensions.cs:

using Microsoft.EntityFrameworkCore;
using Shopfront.Auth;
using Shopfront.Data;
using Shopfront.Failures;
using Shopfront.Fraud;
using Shopfront.Inventory;
using Shopfront.Payments;
using Shopfront.Staff;
using Shopfront.Suppliers;
using Trax.Core.Decisions;
using Trax.Effect.Services.FailureClassifier;
 
namespace Shopfront.Extensions;
 
public static class ShopfrontServiceCollectionExtensions
{
    // Everything Shopfront's trains need, apart from Trax itself.
    public static IServiceCollection AddShopfront(
        this IServiceCollection services,
        string connectionString
    ) =>
        services
            // One context per scope, built for that scope's caller: a pool would share it.
            .AddDbContextFactory<ShopfrontDbContext>(
                options => options.UseNpgsql(connectionString),
                ServiceLifetime.Scoped
            )
            .AddScoped<IShopfrontDbContext>(sp =>
                sp.GetRequiredService<IDbContextFactory<ShopfrontDbContext>>().CreateDbContext()
            )
            .AddScoped<IShopfrontCaller, TraxShopfrontCaller>()
            .AddScoped<Catalogue>()
            .AddSingleton<IPaymentProvider, FakePaymentProvider>()
            .AddSingleton<IFailureClassifier, ShopfrontFailureClassifier>()
            .AddSingleton<IDecider>(FraudRules.Live())
            .AddSingleton<ICandidateFraudDecider, StricterFraudRules>()
            .AddSingleton<IStaffNotifier, LoggingStaffNotifier>()
            .AddSingleton<FakeSupplier>()
            .AddSingleton<ISupplier>(sp => sp.GetRequiredService<FakeSupplier>());
}

SDK Reference

Schedule | AddScheduler | How retries work | Resolve a dead letter | AddLifecycleHook

Next: 10.5 Schedule it, with retries