How to add transactionid code in the AppGW response error page

eenchev 0

Hi there,

Application gateway inserts six additional headers to all requests before it forwards the request to the backend. These headers are:

x-forwarded-for,

x-forwarded-port,

x-forwarded-proto,

x-original-host,

x-original-url,

x-appgw-trace-id

The X-appgw-trace-id is the transactionid which can be checked in the AppGW logs. In f5 LB for example there is an option to put the similarly called support ticket id of the request in the error page (when the WAF blocks certain request). This greatly helps identify quickly a customer issue. So, is there a way to put the Azure appgw transaction id in the error page in a similar way?

Thanks!

KapilAnanth-MSFT 48,081 Reputation points Microsoft Employee

2024-12-03T11:22:11.46+00:00
@eenchev ,

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

As of now, there are no out-of-box solution available to implement this.

You can check Rewrite HTTP headers with Application Gateway, to add, remove, or update HTTP request and response headers

However, currently, I don't see support for "x-appgw-trace-id" in the list of Server variables.

If you wish you may vote in Azure Feedback Hub forum requesting this feature in Server variable.

All the feedback shared in these forums are monitored and reviewed by the Microsoft engineering teams responsible for building Azure.

Additionally, you can also raise a feature request to include this in Application Gateway custom error pages

Thanks,

Kapil

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.
eenchev 0 Reputation points

2024-12-03T12:03:44.5933333+00:00

Hi Kapil,

Thanks for the prompt reply. In this case header rewrite feature won't be useful.

I think some variable or parameter/keyword needs to be included in the html error page which would translate to the actual transaction id. As I mentioned, maybe in a similar way as F5 have implemented it for custom error response with <%TS.request.ID()%>.

https://f5-agility-labs-waf.readthedocs.io/en/latest/class3/module3/lab30/lab3.html

If someone has played with custom error pages or has done something similar please share :)
KapilAnanth-MSFT 48,081 Reputation points Microsoft Employee

2024-12-03T12:48:38.1366667+00:00

@eenchev , I understand the issue.

While it may be not possible to include the Transaction ID into the header as of now, this should be comparatively easy to implement than including the response page.

As Rewrite Rules work at the App Gw level itself, it can parse the Transaction ID.

However, in case of error page (response page), it should pull it from the Azure Monitor logs(which takes some time to generate) and is not ideal.

As of now, I am not aware of any scenario where App gateway modifies the response.

In any case, you can still consider creating a feature request in Azure Feedback Hub forum elaborating your scenario

Cheers,

Kapil
eenchev 0 Reputation points

2024-12-03T13:11:55.9+00:00

Hi,

I am not sure if we are speaking for the same thing. In my opinion logs and azure monitor are not playing a role in this case. Rewrite rules are also in regard to the backend communication.

AppGW already adds this info in the headers after accepting the traffic. It is the x-appgw-trace-id header (transaction id naming used in azure logs). So this info is added at the time the request is being processed by Appgw. I was asking of a way to convey this field in the html error response.

If no other response is received I will consider opening a feature request.

Kind regards,

eenchev
KapilAnanth-MSFT 48,081 Reputation points Microsoft Employee

2024-12-03T14:13:10.55+00:00
@eenchev ,

Wrt,

Rewrite rules are also in regard to the backend communication.

Incorrect.

Rewrite Rules can also be used to influence response headers

This way, client can inspect the response headers (not the body) and arrive at the "x-appgw-trace-id"

For this to happen, Server variables need to support "x-appgw-trace-id"

So I suggested you can raise this is a feedback request

However, if you want the response body to contain the "x-appgw-trace-id",

Then yes, you should raise a feedback incident for this as well.

Thanks for your contribution on Q&A and appreciate much for taking the time to share your feedbacks :)

Cheers,

Kapil

1 answer

eenchev 0 Reputation points

2024-12-04T09:42:59.6133333+00:00

I found that WAF policy for Frontdoor has this already with the "{{azure-ref}}". So probably it can be done for the regional WAF.

Anyone wanting this feature please upvote here : https://feedback.azure.com/d365community/idea/f837b648-78ea-ee11-a73d-000d3adc65a4
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