Advanced - State Processing

[DamianSuess]

Details

This architecture update to advanced state processing overhauls the system, causing incompatibility with previous releases.

What do you get?

• NEW: Async/await states out the box
  • When async/await isn't used, users must exit state method via, ``
• NEW: DefaultStateTimeoutMs (default Timeout.Infinite)
  • Ensures there are no hung states waiting for a result; the show must go on!
• Update: DefaultTimeoutMs renamed to DefaultCommandTimeoutMs to keep it separate from regular states.
• Update: Improved Composite States - deep hierarchy nested states (aka: substate, child state, nested state)
  • Composite state calls OnEntering -> OnEnter, then the initial sub-state. Upon last sub-state, Composite's OnExit is called.
  • Last Sub-State informs parent of it's exiting result via Context.LastChildResult
• Cleanup: Cleaning up test cases and reorganizing TestData for proper reuse. Old code preserved in comments for now.

Benefits

The core framework has been used by Fortune 500 companies, small businesses, robotic frameworks, and more. Now open sourced by Xeno Innovations, Inc.

Improvements over the years have ensured the simplicity and flexibility to scale projects from Proof-of-Concept -> Enterprise general availability.

Sample State Construction

    // ---[ Build MS DI =---
    var services = new ServiceCollection()
      // Register Services
      .AddLogging(b => b.AddSimpleConsole())
      .AddSingleton<IEventAggregator, EventAggregator>()
      .AddSingleton<IDataService, DataService>()

      // Register States
      .AddTransient<EntryInitState>()
      .AddTransient<FetchState>()
      .AddTransient<WaitForMessageState>()
      .AddTransient<WorkflowParent>()
      .AddTransient<DoneState>()
      .AddTransient<ErrorState>()
      .BuildServiceProvider();

    // Factory uses MS-DI to construct states
    // Any DI container can be passed into `ActivatorUtilities.CreateInstance(MY_CONTAINER HERE)`
    Func<Type, object?> factory = t => ActivatorUtilities.CreateInstance(services, t);
    var aggregator = services.GetRequiredService<IEventAggregator>();

    // Supply MS DI factory and aggregator to the state machine
    // Omit `factory` to not use dependency injection
    var machine = new StateMachine<StateId>(factory, aggregator)
    {
      DefaultTimeoutMs = 3000,
    };

    machine.RegisterState<EntryInitState>(StateId.EntryInit, onSuccess: StateId.WorkflowParent);

    machine.RegisterComposite<WorkflowParent>(
      stateId: StateId.WorkflowParent,
      initialChildStateId: StateId.Fetch,
      onSuccess: StateId.Done,
      onError: StateId.Error,
      onFailure: StateId.Error);
    machine.RegisterSubState<FetchState>(
      StateId.Fetch,
      parentId: StateId.WorkflowParent,
      onSuccess: StateId.WaitForMessage);
    machine.RegisterSubState<WaitForMessageState>(
      StateId.WaitForMessage,
      parentId: StateId.WorkflowParent);

    machine.RegisterState<DoneState>(StateId.Done, onSuccess: null);
    machine.RegisterState<ErrorState>(StateId.Error);

    // Without an aggregator, OnMessage won't be called; the command state will timeout in 3000ms:
    var run = machine.RunAsync(StateId.EntryInit, CancellationToken.None);

    await run;