Azure Service bus Queue Size & Topic Size

Question

I want understand the following points regarding the azure service bus more. Need inputs on this.

In Azure Service Bus

Queue Size/Topic Size = Active Messages + Dead Letter Messages + Forward To/Transfer Messages (until they are forwarded) + Scheduled Messages + Transfer Dead letter

What will happen if a message is sent to queue/topic after it reaches the maximum size?

I have configured a Forward to on a subscription(With True Filter) to an another topic and made the topic inactive. When I sent a message on to the topic, since the Forward Topic is not active it has to increase the Transfer Dead Letter Message count ( as per Microsoft Doc https://learn.microsoft.com/en-us/azure/service-bus-messaging/message-counters) but instead it is increasing the Dead Letter Message count.

4.What are the scenarios when filters on subscriptions evaluation failed?

Answer 1

@net 6 newbie Thanks for reaching out.

Service Bus entity consist of?

Total Service Bus size you can add up the sizes of all the messages in the entity (i.e. queue/topic/subscriptions) which are

• ActiveMessageCount: Number of messages in the queue or subscription that are in the active state and ready for delivery.
• ScheduledMessageCount: Number of messages in the scheduled state**.**
• DeadLetterMessageCount: Number of messages in the dead-letter queue
• TransferMessageCount: Number of messages pending transfer into another queue or topic

TransferDeadLetterMessageCount: Number of messages that failed to transfer into another queue or topic and have been moved into the transfer dead-letter queue

Let's say you have a topic and three subscriptions and send one message delivered to all three subscriptions then the total size will be 3 messages size in all subscription.

What will happen if a message is sent to queue/topic after it reaches the maximum size?

If a message is sent to a Service Bus queue or topic after it reaches the maximum size, the message will be rejected, and an exception will be received by the calling code.

I have configured a Forward to on a subscription(With True Filter) to an another topic and made the topic inactive. When I sent a message on to the topic, since the Forward Topic is not active it has to increase the Transfer Dead Letter Message count ( as per Microsoft Doc https://learn.microsoft.com/en-us/azure/service-bus-messaging/message-counters) but instead it is increasing the Dead Letter Message count.

I believed you are talking about Disabled topic state. So in this case as the topic itself is not active so it will increase the dead letter message count as internally when we try to send the message depending on the entity state as disabled. If your entity state was active and it fails to deliver the message in case entity size reached etc then your transfer dead letter message count would have increased.

What are the scenarios when filters on subscriptions evaluation failed?

There could be several scenarios when filters on subscriptions evaluation failed. One of the common scenarios is when the filter expression is not well-formed or contains syntax errors. Another scenario is when the filter expression references a property that does not exist or is not supported by the Service Bus. Additionally, if the filter expression references a user-defined property, but the message does not have that property set, the evaluation will fail. Finally, if the filter expression references a system property, but the message does not have that property set, the evaluation will also fail.

Feel free to get back to me if you have any queries or concerns.

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