MassTransit

MassTransit is a free, open-source distributed application framework for .NET. It enables applications to communicate with each other using message-based communication over a variety of transports.

Elsa provides integration with MassTransit to allow you to dispatch workflow execution requests to a queue for asynchronous execution. Additionally, Elsa provides a MassTransit activity that allows you to send messages to a queue from within a workflow.

Installing MassTransit

To use MassTransit with Elsa, you must first install the following NuGet package:

dotnet add package Elsa.MassTransit --prerelease

Configuring MassTransit

To configure MassTransit, use the UseMassTransit extension method on the IModule argument:

services.AddElsa(elsa => 
{
    elsa.UseMassTransit();
});

MassTransit requires a transport provider to be installed. See MassTransit Transports for more information. If you do not specify a transport provider, MassTransit will use the InMemory transport provider by default.

Elsa provides two optional but convenient packages that install the required transport provider and MassTransit:

• Elsa.MassTransit.AzureServiceBus: Installs the Azure Service Bus transport provider and MassTransit.
• Elsa.MassTransit.RabbitMq: Installs the RabbitMQ transport provider and MassTransit.

Azure Service Bus

To use the Azure Service Bus transport provider, install the Elsa.MassTransit.AzureServiceBus package:

dotnet add package Elsa.MassTransit.AzureServiceBus --prerelease

Next, configure the Azure Service Bus transport provider:

services.AddElsa(elsa => 
{
    elsa.UseMassTransit(massTransit => 
    {
        massTransit.UseAzureServiceBus(
            "connection-string", 
            serviceBusFeature => serviceBusFeature.ConfigureServiceBus = bus => 
            { 
                bus.PrefetchCount = 4;
                bus.LockDuration = TimeSpan.FromMinutes(5);
                bus.MaxConcurrentCalls = 32;
                bus.MaxDeliveryCount = 8;
                // etc.
            }
        );
    });
});

The ConfigureServiceBus delegate allows you to configure the ServiceBusBusFactoryConfigurator instance.

RabbitMQ

To use the RabbitMQ transport provider, install the Elsa.MassTransit.RabbitMq package:

dotnet add package Elsa.MassTransit.RabbitMq --prerelease

Next, configure the RabbitMQ transport provider:

services.AddElsa(elsa => 
{
    elsa.UseMassTransit(massTransit => 
    {
        massTransit.UseRabbitMq(
            "amqp://guest:guest@localhost:5672/elsa", 
            rabbitMqFeature => rabbitMqFeature.ConfigureRabbitMq = bus => 
            { 
                bus.PrefetchCount = 4;
                bus.Durable = true;
                bus.AutoDelete = false;
                bus.ConcurrentMessageLimit = 32;
                // etc. 
            }
        );
    });
});

The ConfigureRabbitMq delegate allows you to configure the RabbitMqBusFactoryConfigurator instance.