Repro

• Create a Standard service bus namespace
• Update the appsettings.json with the connection string in both projects
• Run the ServiceBusSender project
  • This will create an azure-repro topic and a subscription1 subscription
  • It will send 10 messages to the topic
• Run the ServiceBusRepro project
• Observe that 1 message is received by the subscription, and the processor is then stuck

You will see the following output:

      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
      Content root path: /Users/xxx/Projects/ServiceBusRepro/ServiceBusRepro
info: ServiceBusRepro.Worker[0]
      Received message: b44c9cb1a1eb4bf79bca301c08b5b62d
info: ServiceBusRepro.Worker[0]
      Failed to process message: b44c9cb1a1eb4bf79bca301c08b5b62d, retrying

We expect the other messages to be processed (10 in total), but only 1 is processed and the processor is stuck.

Working when prefetch count is 0

Update the Worker.cs L:25 to set the prefetch count to 0:

await using var processor = _serviceBusClient.CreateProcessor(topic, subscription, new ServiceBusProcessorOptions()
{
    PrefetchCount = 0,
    AutoCompleteMessages = false
});

Run the project again, notice the 10 messages now are processed correctly.