Scheduled messages delivery when service bus is down

Question

In continuation with my previous post Azure Service Bus Disaster recovery for messages

I want to know what happens to scheduled messages in service bus if service bus is down (temporarily or disaster occurs). Are they still in service bus backup?

Consider a scenario where service bus was down in a region for some time, I assume messages are not getting lost since downtime was not significant. We can recover them when service bus is up back again.

I see in the below article it says https://docs.microsoft.com/en-us/azure/service-bus-messaging/service-bus-geo-dr

"The fact that no data is replicated means that currently active sessions are not replicated. Additionally, duplicate detection and scheduled messages may not work. New sessions, new scheduled messages and new duplicates will work."

I see scheduled messages getting lost in case of active-passive failover scenario since replication is not present.

But what happens to the scheduled messages if we want to recover them from original pre-failover active service bus. Will they still be present in the service bus?

Answer 1

I want to know what happens to scheduled messages in service bus if service bus is down (temporarily or disaster occurs). Are they still in service bus backup?

These are fundamentally two different scenarios. When temporary outage is taking place, all of the scheduled messages are retained and will show up in the queue when the namespace becomes available. With disaster recovery, on the other hand, we're talking about a catastrophic event where you'll fail over to another namespace.

A disaster is defined as the permanent, or longer-term loss of a Service Bus cluster, Azure region, or datacenter.

As of today, this will not carry over data plane and messages, scheduled or not, will not be transitioned over either. In case the original namespace does recover after the disaster, you will be able to access the scheduled messages that were sent prior to the disaster taking place.