Switchknife.Hosting 0.1.0

Switchknife.Hosting

PollingService, a BackgroundService that does one thing on a timer and never stops the host. Since .NET 6 an exception that leaves ExecuteAsync stops the whole host by default, so a poller that lets one database timeout through takes every endpoint in the process down with it. This base class catches what a poll throws, logs it, backs off and tries again.

public sealed class FeedPoller(FeedClient feeds, IOptions<FeedOptions> options, TimeProvider time, ILogger<FeedPoller> logger)
    : PollingService(time, logger)
{
    protected override string Name => "feeds";
    protected override TimeSpan Interval => options.Value.PollInterval;   // read before every wait

    protected override Task PollAsync(CancellationToken cancellationToken) => feeds.FetchNewAsync(cancellationToken);
}

builder.Services.AddSingleton(TimeProvider.System);
builder.Services.AddHostedService<FeedPoller>();

What the loop does:

1. Polls once on start, then waits. There is no initial delay and no jitter.
2. After a poll that returns: calls OnSucceededAsync, then waits Interval.
3. After a poll that throws anything, an OperationCanceledException from a timeout included: logs a warning {Name} poll failed ({Failures} in a row); next poll in {Delay} with the exception, calls OnFailedAsync(exception), then waits Backoff(Interval, failures, MaxBackoff): the interval doubled per consecutive failure after the first, at most MaxBackoff (default 5 minutes). One success resets the count.
4. A hook that throws is logged as an error, {Name} {Hook} failed, and the loop goes on; a failed OnSucceededAsync does not count as a failed poll.
5. When the host stops, the poll or the wait in progress is cancelled through its token and ExecuteAsync returns without an error. An exception a poll throws once the host is stopping is not caught.

Testing: every wait goes through the TimeProvider passed in, so FakeTimeProvider (Microsoft.Extensions.TimeProvider.Testing) drives the loop without real time passing.

Native AOT: works. samples/Switchknife.AotSmoke runs a poller in a real host under Native AOT: the first poll throws, the host keeps running, the second poll succeeds, the host stops cleanly.

Limits:

• One poll at a time; the next wait starts after the poll and its hook end, so the period is the poll's duration plus the wait, not a fixed rate.
• No scope per poll: resolve scoped services yourself with IServiceScopeFactory inside PollAsync.
• Interval and MaxBackoff are not validated, and an exception from their getters is not caught: both are configuration errors.