Service Bus Provider

The Service Bus provider uses Azure Service Bus for orchestration messaging. It's suitable for scenarios requiring Service Bus integration or existing Service Bus infrastructure.

Installation

dotnet add package Microsoft.Azure.DurableTask.ServiceBus

Configuration

Basic Setup

The Service Bus provider requires separate stores for messaging (Service Bus) and history/state (Azure Storage):

using DurableTask.ServiceBus;
using DurableTask.ServiceBus.Settings;
using DurableTask.ServiceBus.Tracking;
using DurableTask.Core;
using Microsoft.Extensions.Logging;

string serviceBusConnectionString = "Endpoint=sb://mynamespace.servicebus.windows.net/;SharedAccessKeyName=...;SharedAccessKey=...";
string storageConnectionString = "DefaultEndpointsProtocol=https;AccountName=...;AccountKey=...";
string taskHubName = "MyTaskHub";

using ILoggerFactory loggerFactory = LoggerFactory.Create(builder =>
{
    builder.AddConsole();
    builder.SetMinimumLevel(LogLevel.Information);
});

// Create the instance store (Azure Table Storage for history)
var instanceStore = new AzureTableInstanceStore(taskHubName, storageConnectionString);

// Create the blob store (Azure Blob Storage for large messages/sessions)
var blobStore = new AzureStorageBlobStore(taskHubName, storageConnectionString);

// Configure settings
var settings = new ServiceBusOrchestrationServiceSettings();

// Create the orchestration service
var service = new ServiceBusOrchestrationService(
    serviceBusConnectionString,
    taskHubName,
    instanceStore,
    blobStore,
    settings);

await service.CreateIfNotExistsAsync();

var worker = new TaskHubWorker(service, loggerFactory);
var client = new TaskHubClient(service, loggerFactory: loggerFactory);

Using Managed Identity

The Service Bus provider supports managed identity authentication (.NET Standard 2.0+):

using Azure.Identity;
using DurableTask.ServiceBus;
using DurableTask.ServiceBus.Settings;
using DurableTask.ServiceBus.Tracking;

string serviceBusNamespace = "mynamespace.servicebus.windows.net";
Uri storageEndpoint = new Uri("https://mystorageaccount.table.core.windows.net");
Uri blobEndpoint = new Uri("https://mystorageaccount.blob.core.windows.net");
string taskHubName = "MyTaskHub";

var credential = new DefaultAzureCredential();

// Create stores with managed identity
var instanceStore = new AzureTableInstanceStore(taskHubName, storageEndpoint, credential);
var blobStore = new AzureStorageBlobStore(taskHubName, blobEndpoint, credential);

var settings = new ServiceBusOrchestrationServiceSettings();

// Create Service Bus connection with managed identity
var service = new ServiceBusOrchestrationService(
    serviceBusNamespace,  // Just the hostname, not a connection string
    credential,
    taskHubName,
    instanceStore,
    blobStore,
    settings);

Configuration Options

ServiceBusOrchestrationServiceSettings

Setting	Description	Default
MaxTaskOrchestrationDeliveryCount	Max delivery attempts for orchestration messages	10
MaxTaskActivityDeliveryCount	Max delivery attempts for activity messages	10
MaxTrackingDeliveryCount	Max delivery attempts for tracking messages	10
MaxQueueSizeInMegabytes	Maximum queue size for Service Bus queues	1024
PrefetchCount	Message prefetch count	50
TaskOrchestrationDispatcherSettings	Orchestration dispatcher configuration	See below
TaskActivityDispatcherSettings	Activity dispatcher configuration	See below
MessageCompressionSettings	Message compression configuration	Disabled
JumpStartSettings	Jump start (stale instance recovery) settings	Enabled

Dispatcher Settings

Dispatcher settings control concurrency:

var settings = new ServiceBusOrchestrationServiceSettings
{
    TaskOrchestrationDispatcherSettings =
    {
        MaxConcurrentOrchestrations = 100,
        CompressOrchestrationState = true
    },
    TaskActivityDispatcherSettings =
    {
        MaxConcurrentActivities = 100
    }
};

Architecture

Service Bus Resources

The provider creates these Service Bus entities:

Entity Type	Name Pattern	Purpose
Orchestrator Queue	{taskhub}/orchestrator	Orchestration messages
Worker Queue	{taskhub}/worker	Activity messages
Tracking Queue	{taskhub}/tracking	Tracking events

Storage Resources

In addition to Service Bus, the provider uses Azure Storage:

Resource	Name Pattern	Purpose
Instance History Table	InstanceHistory00{taskhub}	Orchestration state and execution history
Jump Start Table	JumpStart00{taskhub}	Pending orchestrations for stale instance recovery
Blob Container	{taskhub}-dtfx	Large messages and session state

Limitations

• Requires both Service Bus and Azure Storage
• Limited query capabilities compared to Azure Storage provider
• Less commonly used — smaller community and fewer examples
• No built-in monitoring dashboard

Next Steps

• Choosing a Backend — Compare all providers
• Durable Task Scheduler — Recommended managed alternative
• Azure Storage Provider — Alternative self-managed option