Azure Service Bus Configuration
MassTransit fully supports Azure Service Bus, including many of the advanced features and capabilities.
Minimal Example
To configure Azure Service Bus, use the connection string (from the Azure portal) to configure the host as shown below.
namespace ServiceBusConsoleListener;using System.Threading.Tasks;using MassTransit;using Microsoft.Extensions.Hosting;public class Program{ public static async Task Main(string[] args) { await Host.CreateDefaultBuilder(args) .ConfigureServices((hostContext, services) => { services.AddMassTransit(x => { x.UsingAzureServiceBus((context, cfg) => { cfg.Host("connection-string"); }); }); }) .Build() .RunAsync(); }}Broker Topology
With Azure Service Bus (ASB), which supports topics and queues, messages are sent or published to topics and ASB routes those messages through topics to the appropriate queues.
Configuration
Azure Service Bus queues includes an extensive set a properties that can be configured. All of these are optional, MassTransit uses sensible defaults, but the control is there when needed.
services.AddMassTransit(x =>{ x.UsingAzureServiceBus((context, cfg) => { cfg.Host("connection-string"); cfg.ReceiveEndpoint("input-queue", e => { // all of these are optional!! e.PrefetchCount = 100; // number of messages to deliver concurrently e.ConcurrentMessageLimit = 100; // default, but shown for example e.LockDuration = TimeSpan.FromMinutes(5); // lock will be renewed up to 30 minutes e.MaxAutoRenewDuration = TimeSpan.FromMinutes(30); }); });});Host Settings
| Property | Type | Description |
|---|---|---|
| TokenCredential | Use a specific token-based credential, such as a managed identity token, to access the namespace. You can use the DefaultAzureCredential to automatically apply any one of several credential types. | |
| TransportType | Change the transport type from the default (AMQP) to use WebSockets |
Receive Settings
| Property | Type | Description |
|---|---|---|
| PrefetchCount | int | The number of unacknowledged messages that can be processed concurrently (default based on CPU count) |
| MaxConcurrentCalls | int | How many concurrent messages to dispatch (transport-throttled) |
| LockDuration | TimeSpan | How long to hold message locks (max is 5 minutes) |
| MaxAutoRenewDuration | TimeSpan | How long to renew message locks (maximum consumer duration) |
| RequiresSession | bool | If true, a message SessionId must be specified when sending messages to the queue |
| MaxDeliveryCount | int | How many times the transport will redeliver the message on negative acknowledgment. This is different from retry, this is the transport redelivering the message to a receive endpoint before moving it to the dead letter queue. |
For example, to configure the transport type to use AMQP over Web Sockets:
cfg.Host(connectionString, h =>{ h.TransportType = ServiceBusTransportType.AmqpWebSockets;});Additional Examples
Example with Azure Managed Identity
The following example shows how to configure Azure Service Bus using an Azure Managed Identity:
services.AddMassTransit(x =>{ x.UsingAzureServiceBus((context, cfg) => { cfg.Host(new Uri("sb://your-service-bus-namespace.servicebus.windows.net")); });});During local development, in the case of Visual Studio, you can configure the account to use under Options -> Azure Service Authentication. Note that your Azure Active Directory user needs explicit access to the resource and have the 'Azure Service Bus Data Owner' role assigned.
Performance
We really recommend that you use the Premium subscription levels for production workloads. We have performed our own testing using MassTransit Benchmark on a P4 instance. It is also critical that your application is in the same DC as the ASB instance. From a home test using a 1Gb fiber connection we could not get over 600/second. When running in the same DC as the ASB we were able to acheive 6k/second. This test was done with one instance writing to ASB and another instance reading from ASB, as adding consumption over the same AMQP connection killed throughput.