microsoft/aspire · warning · OperationCanceledException

Resource ' ' failed to wait for dependencies before the…

Error message

Resource '{resource.Name}' failed to wait for dependencies before the operation was cancelled.

What it means

Wraps an OperationCanceledException raised while waiting for dependency resources, producing a clearer cancellation message via BuildCancellationErrorMessage and rethrowing OperationCanceledException. It signals that the AppHost/resource start was cancelled before dependencies finished waiting.

Solutions

Check whether cancellation was user-initiated (Ctrl+C) — if so, no fix needed; this is expected shutdown behavior.
If cancellation is unintended, extend timeouts in test harnesses / hosting environments and avoid disposing the AppHost prematurely.
Diagnose why the dependency was slow: slow image pulls or health checks can make startup outlast the operator's patience.
Catch OperationCanceledException around AppHost startup/run in host processes to shut down gracefully.

Defensive patterns

Strategy: try-catch

Try / catch

try
{
    await app.StartAsync();
}
catch (OperationCanceledException ex) when (ex.Message.Contains("failed to wait for dependencies"))
{
    logger.LogWarning(ex, "AppHost startup was cancelled while waiting for dependencies.");
}

Prevention

Avoid stopping the AppHost while dependencies are still starting.
Use adequate timeouts in test harnesses that start AppHosts.
Pre-pull large container images to shorten dependency waits.
Treat this as expected on Ctrl+C; only investigate if cancellation is unintended.

When it happens

Trigger: Ctrl+C / AppHost shutdown, debugger stop, or an already-cancelled CancellationToken reaching WaitForDependenciesAsync while one or more Task dependencies are still pending.

Common situations: User cancels the AppHost while a dependency is still starting; Ctrl+C during `aspire run`; test harnesses with short timeouts canceling orchestration; host shutdown triggered by another resource failing fast.

Understand the failure class

Background: Request timed out: what client-side request timeouts mean across libraries (Request timed out, TIMED_OUT, APITimeoutError) — this error's family across 39 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/4e6d171379716d80. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/ApplicationModel/ResourceNotificationService.cs:588

            finally
            {
                pendingDependencyLock.Release();
            }

            if (clearRemainingDependencies)
            {
                await ClearWaitingForDependenciesAsync(resource).ConfigureAwait(false);
            }
        }
        catch (OperationCanceledException ex)
        {
            activity.SetError(ex);

            var errorMessage = BuildCancellationErrorMessage(
                $"Resource '{resource.Name}' failed to wait for dependencies before the operation was cancelled.",
                resource.Name);

            throw new OperationCanceledException(errorMessage, ex, ex.CancellationToken);
        }
        catch (Exception ex)
        {
            activity.SetError(ex);
            throw;
        }
    }

    private Task PublishWaitingForDependenciesAsync(IResource resource, IEnumerable<string> dependencyNames)
    {
        var waitingFor = dependencyNames
            .Where(static dependencyName => !string.IsNullOrWhiteSpace(dependencyName))
            .Distinct(StringComparers.ResourceName)
            .ToArray();

        // Explicit-start resources should not auto-transition to Waiting even if they have dependencies
        // (they should be considered Waiting only after an attempt is made to start them).
        // Resources with no instances managed by Aspire do not "start" from Aspire's perspective,

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