[Azure Application Gateway]Modify existing routing rule to add path based routing

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[Azure Application Gateway]Modify existing routing rule to add path based routing

Arun Menon 25

Hey,

While attempting to incorporate a new routing rule in the Azure portal, I observe the option for path-based routing. However, when I attempt to modify an existing rule, the Azure portal does not seem to provide the provision for adding a path-based rule. Is it not permissible to include path-based routing to an existing rule ?

Azure portal when adding new rule:

User's image

Azure portal when modifying existing rule: User's image

Tushar Kumar 3,371 Reputation points MVP

2023-11-17T09:53:43.17+00:00

Hi Arun,

You can try doing the same using powershell check out the answer by @KapilAnanth-MSFT here : https://learn.microsoft.com/en-us/answers/questions/1221790/update-path-based-rules-under-path-based-routing-i

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Tushar Kumar 3,371 Reputation points MVP

2023-11-17T09:53:43.17+00:00

Hi Arun,

You can try doing the same using powershell check out the answer by @KapilAnanth-MSFT here : https://learn.microsoft.com/en-us/answers/questions/1221790/update-path-based-rules-under-path-based-routing-i

Answer 1

GitaraniSharma-MSFT 50,021 Microsoft Employee Moderator

Hello @Arun Menon ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

I understand that when you try to create a new routing rule in the Azure Application gateway, you get the option for path-based routing, however, when you try to modify an existing rule, it doesn't provide the option to add path-based rules and you would like to know if this is by design.

Yes, this is by design.

When you create a new rule, you choose between basic and path-based :

Basic - if you want to forward all requests on the associated listener (for example, blog.contoso.com/)* to a single backend pool.
Path-based - if you want to route requests from specific URL paths to specific backend pools. The path pattern is applied only to the path of the URL, not to its query parameters.

When you create a rule in Azure Application Gateway, you define its type (basic or path-based) at the time of creation. Once a rule is created, you cannot directly modify its type or change it from basic to path-based or vice versa. You can only edit the settings of the existing rule based on the type on which it was created.

enter image description here

If you need to change the rule type, you have to create a new rule with the desired type and associate the desired listeners and backend pools.

Refer: https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-components#request-routing-rules

https://learn.microsoft.com/en-us/azure/application-gateway/configuration-request-routing-rules

Kindly let us know if the above helps or you need further assistance on this issue.

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.

Alex 495 Reputation points

2023-12-01T14:33:16.5366667+00:00

Hello @GitaraniSharma-MSFT ,

Wouldn't this design cause downtime to the site?

Lets consider this use case, initially we just wanted a basic rule routing all traffic to the backend, but later, if we want to modify the same rule to have some path-based routes to different backends, deleting and recreating the rule would make that listener go down, right?
Is there a way to do this configuration without causing that downtime? similar to other configurations of AppGw (like instance count, etc) can be done on the fly without impact.

Thank you.
GitaraniSharma-MSFT 50,021 Reputation points Microsoft Employee Moderator

2023-12-06T15:12:16.7066667+00:00
Hello @Alex ,

Changes to instance size or count aren't disruptive, and the gateway remains active during this time, but other changes applied on the Application gateway takes some time. So, except the instance count change, all other changes/updates require some time and are not on the fly.

Is there a way to do this configuration without causing that downtime?

The only way I can think to minimize the downtime is as below:

Create a dummy listener.

Create a path-based rule using the dummy listener and the required paths with the existing backend pool and backend settings.

Once the path-based rule is fully configured, delete the basic rule and associate the original listener to the newly created path-based rule.

This should minimize the downtime.

Regards, Gita
Alex 495 Reputation points

2023-12-11T04:40:06.4233333+00:00

Thank you, @GitaraniSharma-MSFT . Let me try this out.

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[Azure Application Gateway]Modify existing routing rule to add path based routing

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