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Update Send Signal to use Dispatch mode

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This fixes potential deadlock and race conditions when a workflow receiving the signal immediately sends a signal back.
This commit is contained in:
Sipke Schoorstra 2021-08-19 20:29:12 +02:00
parent c4b1cf1ee9
commit 014fcf3ca4
1 changed files with 9 additions and 2 deletions
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11
src/core/Elsa.Core/Activities/Signaling/Activities/SendSignal/SendSignal.cs
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@ -3,6 +3,7 @@ using Elsa.Activities.Signaling.Services;
using Elsa.ActivityResults;
using Elsa.Attributes;
using Elsa.Expressions;
using Elsa.Persistence;
using Elsa.Services;
using Elsa.Services.Models;
@ -20,10 +21,12 @@ namespace Elsa.Activities.Signaling
public class SendSignal : Activity
{
private readonly ISignaler _signaler;
private readonly IWorkflowInstanceStore _workflowInstanceStore;
public SendSignal(ISignaler signaler)
public SendSignal(ISignaler signaler, IWorkflowInstanceStore workflowInstanceStore)
{
_signaler = signaler;
_workflowInstanceStore = workflowInstanceStore;
}
[ActivityInput(Hint = "An expression that evaluates to the name of the signal to trigger.", SupportedSyntaxes = new[] { SyntaxNames.JavaScript, SyntaxNames.Liquid })]
@ -37,7 +40,11 @@ namespace Elsa.Activities.Signaling
protected override async ValueTask<IActivityExecutionResult> OnExecuteAsync(ActivityExecutionContext context)
{
await _signaler.TriggerSignalAsync(Signal, Input, correlationId: CorrelationId, cancellationToken: context.CancellationToken);
// Persist the workflow before sending the signal. This fixes a use case where a responding workflow sends a response signal handled by this workflow in a separate branch for example.
await _workflowInstanceStore.SaveAsync(context.WorkflowInstance, context.CancellationToken);
// Trigger the signal synchronously. If we dispatched the signal instead, we don;t have to explicitly save the workflow instance. For future reconsideration.
await _signaler.DispatchSignalAsync(Signal, Input, correlationId: CorrelationId, cancellationToken: context.CancellationToken);
return Done();
}
}