Part 4: Bulk subscriptions

Configure bounded bulk delivery for high-throughput pub/sub consumers

The bulk subscription example combines bulk publishing with a subscription configured for high-throughput ingestion.

Configure batching

Set BulkSubscribe and its limits on the topic attribute:

[DaprTopic(
    "pubsub",
    "telemetry",
    BulkSubscribe = true,
    MaxMessagesCount = 50,
    MaxAwaitDurationMs = 500)]
public sealed class TelemetryBulkHandler : ITopicHandler<DeviceTelemetry>
{
    public Task<TopicResponseAction> HandleAsync(
        DeviceTelemetry reading,
        TopicContext context,
        CancellationToken cancellationToken)
    {
        if (reading.TemperatureCelsius < -273.15 ||
            reading.HumidityPercent is < 0 or > 100)
        {
            return Task.FromResult(TopicResponseAction.Drop);
        }

        return Task.FromResult(TopicResponseAction.Success);
    }
}

MaxMessagesCount bounds the batch size and MaxAwaitDurationMs bounds how long Dapr waits before delivering a partial batch. Choose values based on throughput, latency, and broker behavior. The handler remains responsible for the individual message decision.

Publish single events or batches

await client.PublishEventAsync("pubsub", "telemetry", reading, cancellationToken);

var response = await client.BulkPublishEventAsync(
    "pubsub",
    "telemetry",
    readings,
    options: null,
    cancellationToken: cancellationToken);

Inspect response.FailedEntries when bulk publishing because a batch can contain partial failures.

The unit tests cover valid telemetry and invalid temperature and humidity values. The integration tests publish readings and batches through a real Dapr pub/sub harness to validate the generated bulk subscription configuration and delivery semantics.

dotnet test examples\Messaging\04-BulkSubscribe\BulkSubscribe.Example04.Tests\BulkSubscribe.Example04.Tests.csproj

Next

Last modified September 13, 2026: Updated documentation to include tutorial documentation going through implementation, unit and integration testing for Dapr.Messaging (8c51cf06b)