Application gateway - rules- backend target change with REST/ logic app

Question

Application gateway - rules- backend target change with REST/ logic app

Mazurek, Jakub 100

hi!

I need a button to change the Application gateway - rules- backend target so I decided to go with the Logic app, I started working on in and am trying different REST http requests but none seem to be suited to the cause.

If I just get the appGW settings and just want to switch the target then the body is just huge and I'm getting lost in what to even change as there is a lot of fields that gets changed when I swap them manually and request the body again.

Is there some sort of easy guide to follow with that/ field to use?

Thanks in advance !

Praveen Bandaru 2,665 Reputation points Microsoft External Staff

2025-04-03T17:11:52.55+00:00
Hello Mazurek, Jakub

When working with REST API requests for Azure Application Gateway, especially for modifying backend targets, it can be overwhelming due to the extensive JSON payloads. Here are some steps and tips to simplify the process:

Focus on the backendAddressPools and requestRoutingRules sections in the Application Gateway configuration. These are the primary areas where backend targets are defined and associated with routing rules. Additionally, backendHttpSettingsCollection is crucial as it defines how requests are forwarded to the backend.

Instead of fetching the entire Application Gateway configuration, consider using PATCH requests to update only the specific fields you need. This reduces the complexity of the payload.

If REST API feels too cumbersome, leverage Azure CLI or PowerShell, which are more user-friendly for such tasks. For example, you can use the az network application-gateway rule update command to modify routing rules.

Refer to Microsoft's REST API documentation for Application Gateway for detailed information on the required fields and structure for creating or updating configurations.

The request routing rules guide can help you understand how rules are structured and associated with backend pools.

Use tools like Postman or Azure's API Management to test your REST API calls. This can help you isolate issues and verify the payload structure.

If you're using a Logic App, integrate it with Azure Functions or a custom script to handle the JSON payload manipulation dynamically. This way, you only need to pass the necessary parameters, and the script can construct the full payload for you.

If you wish you may upvote the feedback in the below forum requesting this feature. All the feedback you share in these forums will be monitored and reviewed by the Microsoft engineering teams responsible for building Azure.

Feedback link: https://feedback.azure.com/d365community

Hope the above answer helps! Please let us know do you have any further queries.

Please do consider to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Praveen Bandaru 2,665 Reputation points Microsoft External Staff

2025-04-04T17:22:44.4033333+00:00

Hello Mazurek, Jakub
Just checking in to see if below information was helpful. If you have any further updates on this issue, please feel free to post back.

Hope the above answer helps! Please let us know do you have any further queries.

Please do consider to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Praveen Bandaru 2,665 Reputation points Microsoft External Staff

2025-04-07T18:37:14.0233333+00:00

Hello Mazurek, Jakub
Just checking in to see if below information was helpful. If you have any further updates on this issue, please feel free to post back.

Hope the above answer helps! Please let us know do you have any further queries.

Please do consider to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Mazurek, Jakub 100 Reputation points

2025-04-08T08:22:47.77+00:00

Hi!
sorry for the delay, I was experimenting with the solutions you provided.

I have really hard time putting the changed values.

With AppGW//backendhealth? I can get the values I need and check it really easily but you can't patch or put into that and the only way I found to do that is to use the global appGW settings which is pretty bad- there is hundreds of lines in json and I only want to change one value that's nested pretty low.
Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-10T06:27:18.08+00:00

Hi @Mazurek, Jakub

I just wanted to follow up and see if you had a chance to review my response to your question. Please let us know if it was helpful, and feel free to reach out if you have any further queries.
Mazurek, Jakub 100 Reputation points

2025-04-24T08:22:05.73+00:00

I'm just trying the cmdlet and it seems like there is a lot of things required for it to work but even from my own account trying azure cli it seems like backend pool itself can't be just switched, it requires creation of new rule entirely and then it's possible to swap whole rule with cli, meaning port and priority will be different
Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-24T10:19:03.8533333+00:00

Can you please confirm whether you're making the change through the portal? Specifically, are you able to modify the backend target in the existing rule?

1 answer

Your answer

Praveen Bandaru 2,665 Reputation points Microsoft External Staff

2025-04-04T17:22:44.4033333+00:00

Hello Mazurek, Jakub
Just checking in to see if below information was helpful. If you have any further updates on this issue, please feel free to post back.

Hope the above answer helps! Please let us know do you have any further queries.

Please do consider to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Praveen Bandaru 2,665 Reputation points Microsoft External Staff

2025-04-07T18:37:14.0233333+00:00

Hello Mazurek, Jakub
Just checking in to see if below information was helpful. If you have any further updates on this issue, please feel free to post back.

Hope the above answer helps! Please let us know do you have any further queries.

Please do consider to “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Mazurek, Jakub 100 Reputation points

2025-04-08T08:22:47.77+00:00

Hi!
sorry for the delay, I was experimenting with the solutions you provided.

I have really hard time putting the changed values.

With AppGW//backendhealth? I can get the values I need and check it really easily but you can't patch or put into that and the only way I found to do that is to use the global appGW settings which is pretty bad- there is hundreds of lines in json and I only want to change one value that's nested pretty low.
Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-10T06:27:18.08+00:00

Hi @Mazurek, Jakub

I just wanted to follow up and see if you had a chance to review my response to your question. Please let us know if it was helpful, and feel free to reach out if you have any further queries.
Mazurek, Jakub 100 Reputation points

2025-04-24T08:22:05.73+00:00

I'm just trying the cmdlet and it seems like there is a lot of things required for it to work but even from my own account trying azure cli it seems like backend pool itself can't be just switched, it requires creation of new rule entirely and then it's possible to swap whole rule with cli, meaning port and priority will be different
Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-24T10:19:03.8533333+00:00

Can you please confirm whether you're making the change through the portal? Specifically, are you able to modify the backend target in the existing rule?

Answer 1

Hi @Mazurek, Jakub

The PUT request technically requires the full object to be included in the body.

As tested in my environment, when using a limited set of values in the request body, I received the following error:
User's image

However, when I use the full configuration (as shown below), I'm able to successfully update the Application Gateway.

{
  "location": "eastus",
  "tags": {
    "Environment": "Production"
  },
  "zones": [
    "1",
    "2",
    "3"
  ],
  "properties": {
    "sku": {
      "name": "Basic",
      "tier": "Basic",
      "capacity": 2
    },
    "enableHttp2": true,
    "gatewayIPConfigurations": [
      {
        "name": "appGatewayIpConfig",
        "properties": {
          "subnet": {
            "id": "/subscriptions/830e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/virtualNetworks/appgateway-vnet/subnets/default"
          }
        }
      }
    ],
    "frontendIPConfigurations": [
      {
        "name": "appGwPublicFrontendIpIPv4",
        "properties": {
          "privateIPAllocationMethod": "Dynamic",
          "publicIPAddress": {
            "id": "/subscriptions/8332e60e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/publicIPAddresses/Venkat-pip"
          }
        }
      }
    ],
    "frontendPorts": [
      {
        "name": "port_80",
        "properties": {
          "port": 80
        }
      }
    ],
    "backendAddressPools": [
      {
        "name": "Venkat-pool",
        "properties": {
          "backendAddresses": []
        }
      },
      {
        "name": "Venkat-pool-2",
        "properties": {
          "backendAddresses": [
            {
              "ipAddress": "10.0.0.15"
            },
            {
              "ipAddress": "10.0.0.16"
            }
          ]
        }
      }
    ],
    "backendHttpSettingsCollection": [
      {
        "name": "Demo",
        "properties": {
          "port": 80,
          "protocol": "Http",
          "cookieBasedAffinity": "Disabled",
          "pickHostNameFromBackendAddress": false,
          "requestTimeout": 20
        }
      }
    ],
    "httpListeners": [
      {
        "name": "sample",
        "properties": {
          "frontendIPConfiguration": {
            "id": "/subscriptions/8332bf5e60e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/applicationGateways/venkat-appgateway/frontendIPConfigurations/appGwPublicFrontendIpIPv4"
          },
          "frontendPort": {
            "id": "/subscriptions/8332bf56-7e60e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/applicationGateways/venkat-appgateway/frontendPorts/port_80"
          },
          "protocol": "Http",
          "requireServerNameIndication": false
        }
      }
    ],
    "requestRoutingRules": [
      {
        "name": "demo-pool",
        "properties": {
          "ruleType": "Basic",
            "priority": 100,
          "httpListener": {
            "id": "/subscriptions/83320e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/applicationGateways/venkat-appgateway/httpListeners/sample"
          },
          "backendAddressPool": {
            "id": "/subscriptions/8332b60e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/applicationGateways/venkat-appgateway/backendAddressPools/Venkat-pool-2"
          },
          "backendHttpSettings": {
            "id": "/subscriptions/833260e5f09a9/resourceGroups/Venkat-RG/providers/Microsoft.Network/applicationGateways/venkat-appgateway/backendHttpSettingsCollection/Demo"
          }
        }
      }
    ]
  }
}

Output: User's image

You can update the rule's backend target using just a CLI command

az network application-gateway rule update -g MyResourceGroup --gateway-name MyAppGateway -n MyRule --http-listener MyNewBackendListener

This is the simplest and safest method. No full JSON body required.

If you want to use a Logic App, you can create an Automation Runbook with the above CLI cmdlet and integrate the Runbook into your Logic App, so that you can make the change through the Logic App.

I hope this helps to resolve your issue. Please feel free to ask any questions if the solution provided isn't helpful.

Please don’t forget to close the thread by clicking "Accept the answer" wherever the information provided helps you, as this can be beneficial to other community members.

Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-11T04:39:53.4866667+00:00

Hi @Mazurek, Jakub

I just wanted to follow up and see if you had a chance to review my response to your question. Please let us know if it was helpful, and feel free to reach out if you have any further queries.
Venkat V 1,485 Reputation points Microsoft External Staff

2025-04-14T04:34:55.9733333+00:00

Hi @Mazurek, Jakub

If this answer helped you, please don’t forget to upvote and mark it as accepted to help others in the community.

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Application gateway - rules- backend target change with REST/ logic app

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