Migrating MSMQ subscription messages

If a subscription queue is not configurate when using MSMQ subscription storage in NServiceBus versions 5 and 6, the subscription storage queue automatically defaults to NServiceBus.Subscriptions. However, as this queue name is not endpoint specific, endpoints deployed to the same server could potentially share the same subscriptions queue which is not a good practice.

Therefore, starting from NServiceBus.Transport.Msmq version 1, if a queue called NServiceBus.Subscriptions is detected, an exception will be thrown to prevent potential loss of messages.

To move messages from the NServiceBus.Subscriptions queue to the new queue, refer to the instructions outlined below.

Create the subscriptions queue

Create a transactional queue called .Subscriptions, substituting the actual name of the endpoint. This can be done by with PowerShell scripts, Windows MMC Snap-in, or other tools like QueueExplorer. When creating queues manually using other tools, ensure that the queues are marked transactional.

Using PowerShell

Use the CreateQueue function that's part of CreateQueues.ps1. This PowerShell script comes with the NServiceBus.Transport.Msmq NuGet package and is copied to a subfolder called NServiceBus.Transport.Msmq in the output folder of any project referencing it. Browse to the output folder to locate the scripts, for example, bin\Debug\net472\NServiceBus.Transport.Msmq.

2. Load the CreateQueues.ps1 PowerShell script and run the CreateQueue function as shown below:

    # CreateQueue -QueueName "EndpointName.Subscriptions" -Account $env:USERNAME

Move the subscription messages

Once the new queue is created, use a tool like QueueExplorer to locate the messages in the NServiceBus.Subscriptions queue and move them to the newly created subscriptions queue. If the NServiceBus.Subscriptionsqueue is shared among multiple endpoints, select only the messages intended for the endpoint that is being upgraded to the NServiceBus.Transport.Msmq package. Identify which messages must be moved by inspecting the message body and looking for the event information and by inspecting the subscriber queue name in the LABEL column.

Select the identified messages in the right-hand pane, then right-click and select Cut. Now select the newly created subscriptions queue by clicking on the name of the queue. Right-click on the messages pane and select Paste to move the messages.

Once all the subscription messages have been moved, delete the NServiceBus.Subscriptions queue.