Calling Publish() on MassTransit IPublishEndpoint with Azure Service Bus doesn't return

Question

I experience issues publishing messages to Azure Service Bus using Mass Transit. Calling await Publish() on either IBus or IPublishEndpoint doesnt return. When i switching provider to InMemory it returns as expected.

To narrow down the issue, i used the MassTransit AzureServiceBus sample application https://github.com/MassTransit/Sample-AzureServiceBus . Only setting the connection string in appsettings.json and leaving the default Startup configuration pointing to ASB

services.AddMassTransit(x =>
{
    x.SetKebabCaseEndpointNameFormatter();

    x.UsingAzureServiceBus((_, cfg) =>
    {
        cfg.Host(Configuration.GetConnectionString("AzureServiceBus"));

        cfg.Send<OrderShipped>(s => s.UseSessionIdFormatter(c => c.Message.OrderId.ToString("D")));
    });
});

When hitting the Put() endpoint in ShipmentController the await _publishEndpoint.Publish() call doesn't return. return Ok() is never reached.

namespace Sample.Api.Controllers
{
    using System;
    using System.Threading.Tasks;
    using Contracts;
    using MassTransit;
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.Extensions.Logging;


    [ApiController]
    [Route("[controller]")]
    public class ShipmentController :
        ControllerBase
    {
        readonly ILogger<ShipmentController> _logger;
        readonly IPublishEndpoint _publishEndpoint;

        public ShipmentController(ILogger<ShipmentController> logger, IPublishEndpoint publishEndpoint)
        {
            _logger = logger;
            _publishEndpoint = publishEndpoint;
        }

        [HttpPut]
        public async Task<IActionResult> Put(Guid orderId)
        {
            await _publishEndpoint.Publish(new OrderShipped
            {
                OrderId = orderId,
                Timestamp = DateTimeOffset.Now
            });

            return Ok(new {OrderId = orderId});
        }
    }
}

When switching to InMemory the await _publishEndpoint.Publish() in ShipmentController returns as expected.

services.AddMassTransit(x =>
{
    x.SetKebabCaseEndpointNameFormatter();

    x.UsingInMemory((context, cfg) =>
    {
        cfg.Send<OrderShipped>(s => s.UseSessionIdFormatter(c => c.Message.OrderId.ToString("D")));
    });
});

Answer 1

You should be looking at the logs, but my guess is that your bus is unable to connect to Azure. Firewalls, etc. can be the root cause, it has nothing to do with MassTransit itself.

You should also be passing the CancellationToken from the controller to Publish , so that the call will be canceled if the controller signals cancellation.

Answer 2

I saw the requests on port 5671 being refused in Wireshark. Switching TransportType to AmqpWebSockets (port 443) as suggested here https://stackoverflow.com/a/60333992/1573728 did the trick, so definitely Firewall issue.

services.AddMassTransit(x =>
{
    x.SetKebabCaseEndpointNameFormatter();

    x.UsingAzureServiceBus((_, cfg) =>
    {
        cfg.Host(Configuration.GetConnectionString("AzureServiceBus"), cfg => cfg.TransportType = ServiceBusTransportType.AmqpWebSockets);

        cfg.Send<OrderShipped>(s => s.UseSessionIdFormatter(c => c.Message.OrderId.ToString("D")));
    });
}

In my opinion MassTransit should have thrown an Exception at some point since it wasn't able to publish, or simply because of a timeout.