DuplicateDetection

Duplicate Detection

This sample illustrates the "duplicate detection" feature of Azure Service Bus.

The sample is specifically crafted to demonstrate the effect of duplicate detection when enabled on a queue or topic. The default setting is for duplicate detection to be turned off.

For setup instructions, please refer back to the main README file.

What is duplicate detection?

Enabling duplicate detection will keep track of the MessageId of all messages sent into a queue or topic during a defined time window.

If any new message is sent that carries a MessageId that has already been logged during the time window, the message will be reported as being accepted (the send operation succeeds), but the newly sent message will be instantly ignored and dropped. No other parts of the message are considered.

Read more about duplicate detection in the documentation.

Sample Code

The sample sends two messages that have the same MessageId and shows that only one of those messages is being enqueued and retrievable, if the queue has the duplicate-detection flag set.

The setup template creates the queue for this example by setting the requiresDuplicateDetection flag, which enables the feature, and it sets the duplicateDetectionHistoryTimeWindow to 10 minutes.

{
    "apiVersion": "[variables('apiVersion')]",
    "name": "DupdetectQueue",
    "type": "queues",
    "dependsOn": [
        "[concat('Microsoft.ServiceBus/namespaces/', 
            parameters('serviceBusNamespaceName'))]",
    ],
    "properties": {
	   "requiresDuplicateDetection": true,
       "duplicateDetectionHistoryTimeWindow" :  "T10M"
    },
    "resources": []
},

The sample is further documented inline in the Program.cs C# file.