NLB-7129: update metrics migration steps (#1426)

* NLB-7129: update metrics migration steps

* migration steps for transitioning to platform metrics

* update migration and clarify signal name usage

---------

Co-authored-by: Alan Dooley <a.dooley@f5.com>

Author: rishabh-f5

content/nginxaas-azure/monitoring/migrate-to-platform-metrics.md

@@ -17,20 +17,18 @@ Follow the steps in this section to migrate your deployment monitoring from Cust
 
 1. Verify that your NGINXaaS deployment meets the [pre-requisites]({{< ref "/nginxaas-azure/monitoring/enable-monitoring.md#prerequisites">}}) for Platform metrics to work.
 2. If the pre-requisites are met, Platform metrics are enabled by default on all NGINXaaS deployment. Verify that you are able to see the new metrics in Azure Monitor under the `Standard Metrics` namespace.
-3. Turn off legacy monitoring:
-
-   - Using the Azure portal
-     1. In the Azure portal, go to the **NGINX monitoring** page for your NGINXaaS deployment.
-     2. Turn off the **Send metrics to Azure Monitor** setting.
-     3. Select **Save**.
-
-   - Using Terraform
-     1. Set `diagnose_support_enabled` to false in the `azurerm_nginx_deployment` resource.
-     2. Run `terraform plan` followed by `terraform apply` to upgrade the deployment.
-
-   - Using the Azure CLI
-     Run the following command:
-     ```shell
-     az nginx deployment update --name myDeployment --resource-group \
-     myResourceGroup --enable-diagnostics="false"
-     ```
+3. **Migrate existing alert rules** to use Platform metrics instead of Custom metrics:
+
+   If you have existing alert rules configured for Custom metrics, you need to update them to use the equivalent Platform metrics signals.
+
+   1. In the [Azure portal](https://portal.azure.com), go to **Monitor** > **Alerts**.
+   2. Select **Alert rules**.
+   3. Select the alert rule you want to migrate, then select **Edit**.
+   4. In the **Conditions** tab, select the current **Signal name** to modify it.
+   5. Replace the Custom metrics signal with the corresponding Platform metrics signal:
+      - Platform metrics signals use the `NGINXaaS Standard Metrics` namespace
+   6. The metric name remains the same between Custom and Platform metrics (for example, `nginx.http.request.count`). No update to the signal name is needed.
+   7. Review and adjust the alert logic, thresholds, and conditions as needed.
+   8. Select **Review + create**, then **Create** to save the updated alert rule.
+
+   {{< call-out "note" >}}For a complete list of available Platform metrics, see the [metrics catalog]({{< ref "/nginxaas-azure/monitoring/metrics-catalog.md" >}}). To learn more about editing alert rules, refer to the [Edit an existing alert rule](https://learn.microsoft.com/en-us/azure/azure-monitor/alerts/alerts-create-metric-alert-rule#edit-an-existing-alert-rule) section in the Azure documentation.{{< /call-out >}}