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--- title: Enable duplicate message detection - Azure Service Bus description: This article explains how to enable duplicate message detection using Azure portal, PowerShell, CLI, and programming languages (C#, Java, Python, and JavaScript) ms.topic: how-to ms.date: 04/19/2021 ms.custom: devx-track-azurepowershell, devx-track-azurecli, devx-track-arm-template, devx-track-python ms.devlang: azurecli --- # Enable duplicate message detection for an Azure Service Bus queue or a topic When you enable duplicate detection for a queue or topic, Azure Service Bus keeps a history of all messages sent to the queue or topic for a configure amount of time. During that interval, your queue or topic won't store any duplicate messages. Enabling this property guarantees exactly once delivery over a user-defined span of time. For more information, See [Duplicate detection](duplicate-detection.md). This article shows you different ways to enable duplicate message detection for a Service Bus queue or a topic. > [!NOTE] > - The basic tier of Service Bus doesn't support duplicate detection. The standard and premium tiers support duplicate detection. For differences between these tiers, see [Service Bus pricing](https://azure.microsoft.com/pricing/details/service-bus/). > - You can't enable or disable duplicate detection after the queue or topic is created. You can only do so at the time of creating the queue or topic. ## Using Azure portal When creating a **queue** in the Azure portal, select **Enable duplicate detection** as shown in the following image. You can configure the size of the duplicate detection window when creating a queue or topic. :::image type="content" source="./media/enable-duplicate-detection/create-queue.png" alt-text="Enable duplicate detection at the time of the queue creation"::: When creating a topic in the Azure portal, select **Enable duplicate detection** as shown in the following image. :::image type="content" source="./media/enable-duplicate-detection/create-topic.png" alt-text="Enable duplicate detection at the time of the topic creation"::: You can also configure this setting for an existing queue or topic, if you had enabled duplicate detection at the time of creation. ### Update duplicate detection window size for an existing queue or a topic To change the duplicate detection window size for an existing queue or a topic, on the **Overview** page, select **Change** for **Duplicate detection window**. #### Queue :::image type="content" source="./media/enable-duplicate-detection/window-size.png" alt-text="Set duplicate detection window size for a queue"::: #### Topic :::image type="content" source="./media/enable-duplicate-detection/window-size-topic.png" alt-text="Set duplicate detection window size for a topic"::: ## Using Azure CLI To **create a queue with duplicate detection enabled**, use the [`az servicebus queue create`](/cli/azure/servicebus/queue#az-servicebus-queue-create) command with `--enable-duplicate-detection` set to `true`. ```azurecli-interactive az servicebus queue create \ --resource-group myresourcegroup \ --namespace-name mynamespace \ --name myqueue \ --enable-duplicate-detection true \ --duplicate-detection-history-time-window P1D ``` To **create a topic with duplicate detection enabled**, use the [`az servicebus topic create`](/cli/azure/servicebus/topic#az-servicebus-topic-create) command with `--enable-duplicate-detection` set to `true`. ```azurecli-interactive az servicebus topic create \ --resource-group myresourcegroup \ --namespace-name mynamespace \ --name mytopic \ --enable-duplicate-detection true \ --duplicate-detection-history-time-window P1D ``` The above examples also set the size of the duplicate detection window by using the `--duplicate-detection-history-time-window` parameter. The window size is set to one day. The default value is 10 minutes and the maximum allowed value is seven days. To **update a queue with a new detection window size**, use the [`az servicebus queue update`](/cli/azure/servicebus/queue#az-servicebus-queue-update) command with the `--duplicate-detection-history-time-window` parameter. In this example, the window size is updated to seven days. ```azurecli-interactive az servicebus queue update \ --resource-group myresourcegroup \ --namespace-name mynamespace \ --name myqueue \ --duplicate-detection-history-time-window P7D ``` Similarly, to **update a topic with a new detection window size**, use the [`az servicebus topic update`](/cli/azure/servicebus/topic#az-servicebus-topic-update) command with the `--duplicate-detection-history-time-window` parameter. In this example, the window size is updated to seven days. ```azurecli-interactive az servicebus topic update \ --resource-group myresourcegroup \ --namespace-name mynamespace \ --name myqueue \ --duplicate-detection-history-time-window P7D ``` ## Using Azure PowerShell To **create a queue with duplicate detection enabled**, use the [`New-AzServiceBusQueue`](/powershell/module/az.servicebus/new-azservicebusqueue) command with `-RequiresDuplicateDetection` set to `$True`. ```azurepowershell-interactive New-AzServiceBusQueue -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -QueueName myqueue ` -RequiresDuplicateDetection $True ` -DuplicateDetectionHistoryTimeWindow P1D ``` To **create a topic with duplicate detection enabled**, use the [`New-AzServiceBusTopic`](/powershell/module/az.servicebus/new-azservicebustopic) command with `-RequiresDuplicateDetection` set to `true`. ```azurepowershell-interactive New-AzServiceBusTopic -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -Name mytopic ` -RequiresDuplicateDetection $True -DuplicateDetectionHistoryTimeWindow P1D ``` The above examples also set the size of the duplicate detection window by using the `-DuplicateDetectionHistoryTimeWindow` parameter. The window size is set to one day. The default value is 10 minutes and the maximum allowed value is seven days. To **update a queue with a new detection window size**, see the following example. In this example, the window size is updated to seven days. ```azurepowershell-interactive $queue=Get-AzServiceBusQueue -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -QueueName myqueue $queue.DuplicateDetectionHistoryTimeWindow='P7D' Set-AzServiceBusQueue -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -QueueName myqueue ` -QueueObj $queue ``` To **update a topic with a new detection window size**, see the following example. In this example, the window size is updated to seven days. ```azurepowershell-interactive $topic=Get-AzServiceBusTopic -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -Name mytopic $topic.DuplicateDetectionHistoryTimeWindow='P7D' Set-AzServiceBusTopic -ResourceGroup myresourcegroup ` -NamespaceName mynamespace ` -Name mytopic ` -TopicObj $topic ``` ## Using Azure Resource Manager template To **create a queue with duplicate detection enabled**, set `requiresDuplicateDetection` to `true` in the queue properties section. For more information, see [Microsoft.ServiceBus namespaces/queues template reference](/azure/templates/microsoft.servicebus/namespaces/queues?tabs=json). Specify a value for the `duplicateDetectionHistoryTimeWindow` property to set the size of the duplicate detection window. In the following example, it's set to one day. ```json { "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#", "contentVersion": "1.0.0.0", "parameters": { "serviceBusNamespaceName": { "type": "string", "metadata": { "description": "Name of the Service Bus namespace" } }, "serviceBusQueueName": { "type": "string", "metadata": { "description": "Name of the Queue" } }, "location": { "type": "string", "defaultValue": "[resourceGroup().location]", "metadata": { "description": "Location for all resources." } } }, "resources": [ { "type": "Microsoft.ServiceBus/namespaces", "apiVersion": "2018-01-01-preview", "name": "[parameters('serviceBusNamespaceName')]", "location": "[parameters('location')]", "sku": { "name": "Standard" }, "properties": {}, "resources": [ { "type": "Queues", "apiVersion": "2017-04-01", "name": "[parameters('serviceBusQueueName')]", "dependsOn": [ "[resourceId('Microsoft.ServiceBus/namespaces', parameters('serviceBusNamespaceName'))]" ], "properties": { "requiresDuplicateDetection": true, "duplicateDetectionHistoryTimeWindow": "P1D" } } ] } ] } ``` To **create a topic with duplicate detection enabled**, set `requiresDuplicateDetection` to `true` in the topic properties section. For more information, see [Microsoft.ServiceBus namespaces/topics template reference](/azure/templates/microsoft.servicebus/namespaces/topics?tabs=json). ```json { "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#", "contentVersion": "1.0.0.0", "parameters": { "service_BusNamespace_Name": { "type": "string", "metadata": { "description": "Name of the Service Bus namespace" } }, "serviceBusTopicName": { "type": "string", "metadata": { "description": "Name of the Topic" } }, "location": { "type": "string", "defaultValue": "[resourceGroup().location]", "metadata": { "description": "Location for all resources." } } }, "resources": [ { "apiVersion": "2018-01-01-preview", "name": "[parameters('service_BusNamespace_Name')]", "type": "Microsoft.ServiceBus/namespaces", "location": "[parameters('location')]", "sku": { "name": "Standard" }, "properties": {}, "resources": [ { "apiVersion": "2017-04-01", "name": "[parameters('serviceBusTopicName')]", "type": "topics", "dependsOn": [ "[resourceId('Microsoft.ServiceBus/namespaces/', parameters('service_BusNamespace_Name'))]" ], "properties": { "requiresDuplicateDetection": true, "duplicateDetectionHistoryTimeWindow": "P1D" } } ] } ] } ``` ## Next steps Try the samples in the language of your choice to explore Azure Service Bus features. - [Azure Service Bus client library samples for .NET (latest)](/samples/azure/azure-sdk-for-net/azuremessagingservicebus-samples/) - [Azure Service Bus client library samples for Java (latest)](/samples/azure/azure-sdk-for-java/servicebus-samples/) - [Azure Service Bus client library samples for Python](/samples/azure/azure-sdk-for-python/servicebus-samples/) - [Azure Service Bus client library samples for JavaScript](/samples/azure/azure-sdk-for-js/service-bus-javascript/) - [Azure Service Bus client library samples for TypeScript](/samples/azure/azure-sdk-for-js/service-bus-typescript/) Find samples for the older .NET and Java client libraries below: - [Azure Service Bus client library samples for .NET (legacy)](https://github.com/Azure/azure-service-bus/tree/master/samples/DotNet/Microsoft.Azure.ServiceBus/) - [Azure Service Bus client library samples for Java (legacy)](https://github.com/Azure/azure-service-bus/tree/master/samples/Java/azure-servicebus) [!INCLUDE [service-bus-track-0-and-1-sdk-support-retirement](../../includes/service-bus-track-0-and-1-sdk-support-retirement.md)]