NserviceBus - What happens to a message if the server is offline

Question

I went thought NServiceBus documentation including the durable messaging one. What I understand is that when the server is offline the messages continue to go into the server's input queue which get picked up when server comes back online.

But what if the server is completely down and the input queue is not accessible?

I'm using Bus.Send from the client.

Answer 1

It depends on what transport you're using.

In the case of a brokered message queue, like Azure Service Bus, as long as that service is available, the fact the machine that will eventually retrieve the messages is offline is irrelevant, as that machine is simply asking the external queuing service for messages. The same goes for a transport like SQL Server.

In the case of a transport like MSMQ, which is a store a forward style queue, the messages will remain in a local outgoing queue until the remote machine becomes available.

Answer 2

Can you double check that you are looking in the correct spot? If you aren't getting an error out of NServiceBus when you Send, then MSMQ is installed. If it can't be reached or the service is stopped you should get errors.

The Outbound queues are in a different place as illustrated here: http://blogs.msdn.com/cfs-filesystemfile.ashx/__key/communityserver-components-postattachments/00-09-06-31-16/outgoingempty.JPG

As RMD indicated, this is an advantage of the store and forward MSMQ transport.. the local outbound queue should just stack these up until the remote server is available.

Thx. Joe