Wrong http hostname in app service diagnostic settings export

fhtino 161

I have an App Service (linux) with multiple custom domains. Everything is working fine. I can access my site with different names: https://mysite.azurewebsites.net https://www.mydomainA.com https://www.mydomainB.org etc.

On the App Service, I have also activated the Diagnostic Settings export to Storage Account and to Log Analytics. In the StorageAccount I can find the json-lines .pt1h files and in the LogAnalytics data are stored in AppServiceHTTPLogs.

Problem: in both cases, json files and AppServiceHTTPLogs, the field CsHost is always filled with "mysite.azurewebsites.net" instead of the real hostnames used by browsers to reach my site: "www.mydomainA.com" and "www.mydomainB.org"

Is this the expected beahavior (I hope not)? Is there a way to fill the log (json and loganalytics) with the right hostname?

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VenkateshDodda-MSFT 23,786 Reputation points Microsoft Employee

2023-01-23T08:49:27.6733333+00:00

@fhtino Thank you for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.

Is this the expected beahavior (I hope not)?

No, all the requests that were passed through specific hostname will be get recorded in CsHost column.
To reproduce this behavior, I have created sample asp.net application hosted on app service (running on windows app service plan, dotnetv6.0) created couple of host bindings and enabled the diagnostic settings to log analytics workspace and to storage account as well.

While querying the AppserviceHTTPLogs from log analytics workspace, we are able to see the different hostname bindings in CsHost column through which the request is being served as shown below.

Even in storage account logs also I am able to see the different hostname bindings as well as shown below.

could please check whether the hostname bindings for the webapp were configured correctly or not and also are the above requests that you have shown are they making request from the correct hostname?
fhtino 161 Reputation points

2023-01-23T16:52:27.23+00:00

@VenkateshDodda-MSFT Thank you for your support.

The Custom Domains mapping is perfectly working. Also https certificates are OK.

Users (thousands) are reaching my sites using custom domains . And the web application is working correctly.

More info: mine is a Linux app-service, running php 8.1. Your tests used a .netcore app. Is behavior on php 8.1 different?
fhtino 161 Reputation points

2023-01-26T16:42:53.71+00:00

@VenkateshDodda-MSFT do you have any feedback?
VenkateshDodda-MSFT 23,786 Reputation points Microsoft Employee

2023-01-27T04:57:25.77+00:00

@fhtino Thanks for sharing more information on this apologize for the delay in my response.

I have created a web app(running on Linux with php8.1) and looked at the AppServiceHTTPLogs from both log analytics and from .json file stored in storage account.In CsHost column we can see only either the webapp root url(app-name.azurewebsites.net) or scm URL (app-name.scm.azure.websites.net) instead of the webapp hostnames.

I am checking with the team internally on this will get back to you once we have any updates.
VenkateshDodda-MSFT 23,786 Reputation points Microsoft Employee

2023-02-01T06:36:43.4433333+00:00

@fhtino We received your feedback that the answer provided on the thread was not helpful.

Thank you for taking time to share your feedback.

Kindly let us know how we can help you further on the thread to your satisfaction. We are here to help you and strive to make your experience better and greatly value your feedback.

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Looking forward to your reply. Much appreciate your feedback!

Accepted answer

VenkateshDodda-MSFT 23,786 Reputation points Microsoft Employee

2023-01-31T06:16:35.66+00:00

@fhtino Thanks for your patience on this! I have checked with our App Service engineering team, they have confirmed that it's a bug, and the fix will be released in the next update (over few months | we don't have an exact ETA to share).

As and when I have more information, I'll share the update here.

At this moment, we don't have any workaround to add those custom hostname's in AppserviceHTTPLogs for Linux apps.

Once again, thanks for reporting this issue. We appreciate your patience!

Feel free to reach back to me if you have any further questions on this.
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fhtino 161 Reputation points

2023-02-01T05:34:49.8866667+00:00

@VenkateshDodda-MSFT is there any public github issue or something similar to track this bug and check progress?

VenkateshDodda-MSFT 23,786 Reputation points Microsoft Employee

2023-02-01T06:39:47.96+00:00

@fhtino Thanks for your response. You can use this thread to track the updates on this issue, as soon as I have more updates from engineering team I will post here.

I am also checking with team internally to see if there is any GitHub issue or blog post to track.
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