Signals

Signals let the outside world talk to a running workflow: a human approval, a webhook, a payment confirmation. The workflow parks until the signal arrives, and signals are persisted so nothing is lost across restarts.

Waiting for a signal

[Workflow("approval")]
public sealed class ApprovalWorkflow
{
    [WorkflowRun]
    public async ValueTask<string> RunAsync(
        IWorkflowContext ctx,
        string request,
        CancellationToken cancellationToken
    )
    {
        var decision = await ctx.WaitForSignal<ApprovalDecision>("approval", cancellationToken);
        return decision.Approved ? $"{request} approved." : $"{request} rejected.";
    }
}

Sending a signal

Send through the handle you got when starting the workflow, or through the client with a run id:

await handle.SignalAsync(
    "approval",
    new ApprovalDecision(Approved: true, UserId: "era", Comment: "Ship it"),
    idempotencyKey: $"approval:{handle.WorkflowRunId:N}"
);

Delivery semantics