How to specify the sender subscription in a message in azure service bus topic subscription?

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In azure servicebus I have a topic with a subscription. When this topic recieved a message, the subscription must forward the message to a logging-queue. How can I specify that the forwarded message is from this topic? I need the name of topic in the forwarded message.

I tried this but does not work. I dont know if Im doing wrong.

az servicebus topic subscription rule create --resource-group myresourcegroup --namespace-name mynamespace --topic-name mytopic --subscription-name mysubscription --name myrule --sql-action-expression myproperty=myvalue
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azureazureservicebusservicebusazure-servicebus-topicsazure-servicebus-subscriptions
Can you not add topic name as one of the custom properties in the message itself while sending? - Gaurav Mantri
No I dont think so. I did not find any option which do that in topic rules or subscription rules. Is that possible to do? if so how? - milan-W
Not through the rules but when you send a message you can define zero or more custom properties. For example, if you're using Azure Service Bus SDK for .Net, Message class has a property called. UserProperties. You can add topic name there and send the message to the topic. More on UserProperties can be found here: docs.microsoft.com/en-us/dotnet/api/…. - Gaurav Mantri
Yeah, Ofc I do that. In the message property I added TopicName. But since I have several Topics, so I want that the name of the Topic which forwards a message to be set while forwarding. The message has a TopicName property which is empty when a user send the message to the topic, and it is OK. But when the topic got the message, the subscription in the topic must forward the message to a queue. In this forwarding I need the name of topic in the message. I want something like Set TopicName=%topicname% just befor forwarding. - milan-W
I think you're confusing between a Topic and a Subscription. If I am not mistaken, you need the name of the Subscription from where the message is forwarded to as a message sent to a topic can be received by 0 or more subscriptions based on the filtering rules. - Gaurav Mantri

1 Answers

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Messages that have specific characteristics must be processed in different ways. To enable this processing, you can configure subscriptions to find messages that have desired properties and then perform certain modifications to those properties. While Service Bus subscriptions see all messages sent to the topic, you can only copy a subset of those messages to the virtual subscription queue.

This filtering is accomplished using subscription filters. Such modifications are called filter actions. When a subscription is created, you can supply a filter expression that operates on the properties of the message, both the system properties (for example, Label) and custom application properties (for example, StoreName.)

For a full working example, see the TopicSubscriptionWithRuleOperationsSample sample on GitHub.