Hi, I am deploying Azure Event Hub using the Azurerm Terraform provider and have also configured several alerts, such as highIncomingBytes and highEventHubSize . The threshold values for these alerts are based on the number of Throughput Units (TUs) assigned to the Event Hub. However, since Auto-Inflate is enabled, the TUs can increase automatically based on demand. In such cases, the alert thresholds should also be dynamically adjusted according to the current TU value. I would like to understand how I can detect changes in TU count , retrieve the correct value, and update the alert thresholds accordingly when deploying via Terraform. Your guidance on this would be greatly appreciated. Thank you for your time and support.

Hi @Bharata, Swapnil Welcome to Microsoft Q&A platform and thanks for posting your query here. To detect changes in the number of Throughput Units (TUs) and dynamically adjust your alert thresholds when Auto-Inflate is enabled for an Azure Event Hub namespace, you can follow these steps: Monitor Throughput Units Using Azure Metrics: Azure provides a metric called Throughput Unit under the Event Hub namespace monitoring. You can track this metric to observe changes in TU usage. This metric reflects the current number of TUs assigned to the namespace, including any changes due to Auto-Inflate. Retrieve Current TU Count Programmatically: Use Azure Monitor REST API or Azure CLI to query the Throughput Unit metric in near real-time. Alternatively, you can leverage the Azure Terraform provider's azurerm_monitor_metric_alert to capture the metric data and build custom workflows. Update Terraform Alert Thresholds Dynamically: Unfortunately, Terraform does not support dynamic metric-based configurations out of the box. However, you can achieve this by: -Integrating a scripting mechanism (e.g., a Python script or Azure Function) that fetches the current TU count via Azure Monitor API. -Use this script to calculate and update the alert thresholds dynamically based on the TU value. -Re-run the Terraform configuration to apply the updated thresholds. Consider Using Log Analytics or Alerts with Azure Monitor: Instead of manually adjusting alert thresholds, you can use dynamic thresholds in Azure Monitor. Dynamic thresholds automatically adjust based on historical data trends and might reduce the need for manual intervention. Reference: https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-auto-inflate?source=recommendations https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-scalability?source=recommendations Hope this helps. Do let us know if you any further queries. If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

How can we detect an increase in Throughput Units (TUs) when Auto-Inflate is enabled for an Azure Event Hub namespace?

Accepted answer

Smaran Thoomu 19,955 Reputation points Microsoft Vendor

2025-02-06T14:51:09.0833333+00:00
Hi @Bharata, Swapnil

Welcome to Microsoft Q&A platform and thanks for posting your query here.
To detect changes in the number of Throughput Units (TUs) and dynamically adjust your alert thresholds when Auto-Inflate is enabled for an Azure Event Hub namespace, you can follow these steps:

Monitor Throughput Units Using Azure Metrics: Azure provides a metric called Throughput Unit under the Event Hub namespace monitoring. You can track this metric to observe changes in TU usage. This metric reflects the current number of TUs assigned to the namespace, including any changes due to Auto-Inflate.

Retrieve Current TU Count Programmatically: Use Azure Monitor REST API or Azure CLI to query the Throughput Unit metric in near real-time. Alternatively, you can leverage the Azure Terraform provider's azurerm_monitor_metric_alert to capture the metric data and build custom workflows.

Update Terraform Alert Thresholds Dynamically: Unfortunately, Terraform does not support dynamic metric-based configurations out of the box. However, you can achieve this by:

-Integrating a scripting mechanism (e.g., a Python script or Azure Function) that fetches the current TU count via Azure Monitor API.

-Use this script to calculate and update the alert thresholds dynamically based on the TU value.

-Re-run the Terraform configuration to apply the updated thresholds.

Consider Using Log Analytics or Alerts with Azure Monitor: Instead of manually adjusting alert thresholds, you can use dynamic thresholds in Azure Monitor. Dynamic thresholds automatically adjust based on historical data trends and might reduce the need for manual intervention.

Reference: https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-auto-inflate?source=recommendations

https://learn.microsoft.com/en-us/azure/event-hubs/event-hubs-scalability?source=recommendations

Hope this helps. Do let us know if you any further queries.

If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
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1 person found this answer helpful.
Bharata, Swapnil 0 Reputation points

2025-02-06T17:13:26.7966667+00:00

@Smaran Thoomu Thank you very much for your detailed response and step-by-step guidance.

I was curious to know where I can find the Throughput Unit metric you mentioned. I checked the Metrics list under the Monitoring section for the Azure Event Hub namespace but couldn't find it. Could you please guide me on where to locate it?

Thank you!

Bharata, Swapnil 0 Reputation points

2025-02-06T17:15:52.6633333+00:00

@Smaran Thoomu Also I have gone through following metrics list that supported by Azure Event Hub Namespace. But unfortunately I didn't find metric named Throughput Unit

https://learn.microsoft.com/en-us/azure/azure-monitor/reference/supported-metrics/microsoft-eventhub-namespaces-metrics

Smaran Thoomu 19,955 Reputation points Microsoft Vendor

2025-02-10T09:01:05.8666667+00:00

Hi @Bharata, Swapnil

Thanks for your follow-up and for pointing this out. You’re absolutely right that the specific “Throughput Unit” metric isn’t listed in Azure Monitor metrics for Event Hub namespaces. I can see how that might be confusing when trying to track TU usage directly. Let me clarify a few things and offer some suggestions that could help:

Monitoring Throughput Unit (TU) Usage

Azure doesn’t provide a direct “Throughput Unit” metric in the Metrics blade of the Event Hub namespace. However, you can infer TU allocation indirectly by monitoring metrics such as:

Incoming Bytes: Reflects the volume of incoming data.

Outgoing Bytes: Reflects the volume of outgoing data.

Incoming Messages: The number of messages/events being processed.

When Auto-Inflate is enabled, TUs are scaled up automatically as these metrics increase, so tracking them gives you an idea of how TUs are being utilized.

Retrieving TU Allocation Directly

If you want to find the exact number of TUs allocated to your namespace at any given time, you can use the following methods:

Azure CLI Run the command:
az eventhubs namespace show --resource-group <ResourceGroupName> --name <NamespaceName>
Look for the sku.capacity value, which reflects the current TU count.

Azure Resource Manager (ARM) API Use the GET API call for the namespace:
GET /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.EventHub/namespaces/{namespaceName}
The sku.capacity property will give you the current TU count.

Azure Portal You can also check the current TU allocation under the “Settings” section for the Event Hub namespace in the Azure portal.

Adjusting Alert Thresholds Dynamically

Terraform doesn’t currently support automatically adjusting alert thresholds based on real-time metric values. However, you can implement a custom solution using a script or an Azure Function:

Query the current TU allocation periodically using the ARM API or Azure CLI.

Update the alert thresholds dynamically based on TU count.

Reapply the updated Terraform configuration to reflect the new thresholds.

If you’re looking for a simpler alternative, you might consider enabling dynamic thresholds for your alerts directly in Azure Monitor. These thresholds adjust automatically based on historical data patterns and might reduce the need for manual updates.

I hope this information helps. Let me know if you have any further questions.

Smaran Thoomu 19,955 Reputation points Microsoft Vendor

2025-02-11T12:18:43.72+00:00

@Bharata, Swapnil Following up to see if the above suggestion was helpful. And, if you have any further query do let us know.

Bharata, Swapnil 0 Reputation points

2025-02-11T12:25:54.2966667+00:00

@Smaran Thoomu I implemented the solution you suggested, using an Azure CLI command to retrieve the current Throughput Unit (TU) count and passing it to the Terraform template to redeploy the Azure Event Hub with the updated configuration. This approach worked successfully.

However, I observed an unexpected behavior—when redeploying the Terraform template, the zone_redundant flag changed its value. As a result, Terraform destroyed and recreated the Event Hub instead of applying only the necessary updates.

Would you know the reason behind this behavior?

Smaran Thoomu 19,955 Reputation points Microsoft Vendor

2025-02-12T10:19:21.62+00:00

Hi Bharata, Swapnil
Thanks for following up! I’m glad to hear that retrieving the Throughput Unit (TU) count using Azure CLI and passing it to Terraform worked for you!

Regarding the zone_redundant flag changing during redeployment, this typically happens because Terraform treats certain settings as immutable. If Terraform detects a difference in the configuration (even if it's not intentional), it may destroy and recreate the resource instead of just updating it.

Here are a few possible reasons why this is happening:

Terraform State vs. Azure Defaults – Sometimes, if a parameter like zone_redundant isn’t explicitly defined in your Terraform template, Azure might assign a default value. When you redeploy, Terraform notices the difference and thinks a full replacement is needed.

Implicit Dependency on SKU Changes – Since zone_redundant is tied to the SKU type, any indirect changes to SKU settings (e.g., TU count updates) might affect how Terraform interprets the configuration.

Terraform Provider Behavior – The AzureRM Terraform provider may require explicit settings for zone_redundant to prevent accidental changes.

How to Fix It

xplicitly define zone_redundant in your Terraform template to ensure it stays consistent across deployments.

Use terraform plan before applying changes to check if any unexpected updates are being triggered.

Check if the AzureRM provider version matters – older versions might handle this setting differently.

I hope this information helps. Let me know if you have any further questions.

Bharata, Swapnil 0 Reputation points

2025-02-12T13:03:31.13+00:00

@Smaran Thoomu Thank you so much for above information. After explicitly setting the zone_redundant value in the Terraform template, the Event Hub is now correctly updating its configuration instead of being recreated, as expected.

Smaran Thoomu 19,955 Reputation points Microsoft Vendor

2025-02-12T13:13:31.8333333+00:00

Bharata, Swapnil Glad to hear that setting zone_redundant fixed the issue! Let me know if you need any more help.
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How can we detect an increase in Throughput Units (TUs) when Auto-Inflate is enabled for an Azure Event Hub namespace?

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