Prompter

A lil' helper library for Service Fabric actor's reminders.

It adds two things we found ourselves implementing over and over again:

• Safe unregistering of reminders

  No more try/catch blocks! Huzzah!

• Single-use reminders

  You're meant to unregister reminders, even if you're using the fire-once approach (dueTime: TimeSpan.FromMilliseconds(-1)). This makes that process automatic with PromptOnce. This is currently listed as a functional bug, but this will get you around it.

• Correlation IDs

  We use found it super useful to have an ID we could track across all of our services. This let's you track a GUID across reminders.

Usage

internal sealed class OrderActor : PromptableActor, IOrderActor
{
    public async Task PlaceOrder(OrderRequest req)
    {
        // Some internal logic, whatever
        var token = await SetOrderState(req);

        // Register a prompt to come back in seven days
        await PromptOnce(token, TimeSpan.FromDays(7));
    }

    protected override async Task OnPrompt(string name, byte[] context, TimeSpan due, TimeSpan period, Guid cid)
    {
        var token = name;
        var order = await GetOrderState(name);
        await SendEmailReminder(order);
    }
}

Setup

Install it from NuGet (Install-Package Prompter) and use one of the two options for integration.

A. Inheritance

internal sealed class MyActor : PromptableActor, IMyActor { }

B. Pretending you have traits

Setup a callback:

private Task OnPrompt(string name, byte[] context, TimeSpan due, TimeSpan period, Guid cid)
{
    // Do stuff
}

then add it to your actor's constructor:

private readonly Prompt _prompt;

public ActorFixture(ActorService svc, ActorId id)
: base(svc, id)
{
    _prompt = new Prompt(
        OnPrompt,
        GetReminder,
        RegisterReminderAsync,
        UnregisterReminderAsync,
        this);
}

and link the reminder callback to Prompter:

public Task ReceiveReminderAsync(string reminderName, byte[] state, TimeSpan dueTime, TimeSpan period) =>
    _prompt.ReceivePrompt(reminderName, state, dueTime, period);

It's awful, isn't it? I couldn't figure out a nicer way layer it on but I'm open to suggestions. (We have a bunch of these 'traits' we wanted to use and didn't like the idea of bundling them all into one base class.)

Logging

You should be logging everything like crazy, so I chucked in logs here too. That's why you (should) pass in the current actor when constructing Prompt. (I don't do anything else with it, I swear!)

The provider is Prompter-Prompt and it logs registers, unregisters and receives.