Override backend path not working as expected

Question

Override backend path not working as expected

Erik Magnusson 45

Hello,

I have an application gateway (WAF V2) using path based routing with several app services configured in the following way:

mydomain.com -> foo.azurewebsites.net

mydomain.com/bar* -> bar.azurewebsites.net

The root route to the foo app is working as expected but I'm having trouble routing to the bar app in a satisfactory manner.

According to this: https://learn.microsoft.com/en-us/azure/application-gateway/configuration-http-settings the overridden path should be forwarded to the backend service. Therefore I expect it to work in the following way:

Request for mydomain.com/bar -> Redirected to bar.azurewebsites.net

Request for mydomain.com/bar/login -> Redirected to bar.azurewebsites.net/login

Request for mydomain.com/bar/site.css -> Redirected to bar.azurewebsites.net/site.css

What is actually happening:

Request for mydomain.com/bar -> Redirected to bar.azurewebsites.net (working correctly)

Request for mydomain.com/bar/login -> Redirected to foo.azurewebsites.net/login (which doesn't exist)

Request for mydomain.com/bar/site.css -> Redirected to foo.azurewebsites.net/site.css (which doesn't exist)

It would seem the override is not actually forwarding the path to the backend but instead overriding the path before it hits the path based rule, leading to the requests being routed to the foo app instead of to the bar app.

As of now, the only way I've been able to solve the path based routing is by creating a virtual directory in the app service set to /bar and point this to the wwwroot or publishing in a sub directory. This is less than ideal however since one cannot remove the original path /.

Is there any way to achieve what I want to accomplish using path based routing and overriding path?

Thanks.

Priya Kumar 1,096 Reputation points Microsoft Employee

2023-03-02T14:13:01.0633333+00:00

Hello @Eric Magnusson

Thanks for reaching Q&A platform.

Would like to explain you the understanding about the “Path Based Routing” and “override backend path”.

· When the HTTP setting is attached to a basic request-routing rule:

|Original
request|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | |/home/|/override/|/override/home/| |/home/secondhome/|/override/|/override/home/secondhome/|

· When the HTTP setting is attached to a path-based request-routing rule:

|Original
request|Path rule|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | -------- | |/pathrule/home/|/pathrule*|/override/|/override/home/| |/pathrule/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/home/|/pathrule*|/override/|/override/home/| |/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/pathrule/home/|/pathrule/home*|/override/|/override/| |/pathrule/home/secondhome/|/pathrule/home*|/override/|/override/secondhome/| |/pathrule/|/pathrule/|/override/|/override/|

Document: https://learn.microsoft.com/en-us/azure/application-gateway/configuration-http-settings#override-backend-path

Please elaborate the issue, if your query is still not been answered.
Priya Kumar 1,096 Reputation points Microsoft Employee

2023-03-02T14:13:20.08+00:00

Hello @Eric Magnusson

Thanks for reaching Q&A platform.

Would like to explain you the understanding about the “Path Based Routing” and “override backend path”.

· When the HTTP setting is attached to a basic request-routing rule:

|Original
request|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | |/home/|/override/|/override/home/| |/home/secondhome/|/override/|/override/home/secondhome/|

· When the HTTP setting is attached to a path-based request-routing rule:

|Original
request|Path rule|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | -------- | |/pathrule/home/|/pathrule*|/override/|/override/home/| |/pathrule/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/home/|/pathrule*|/override/|/override/home/| |/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/pathrule/home/|/pathrule/home*|/override/|/override/| |/pathrule/home/secondhome/|/pathrule/home*|/override/|/override/secondhome/| |/pathrule/|/pathrule/|/override/|/override/|

Document: https://learn.microsoft.com/en-us/azure/application-gateway/configuration-http-settings#override-backend-path

Please elaborate the issue, if your query is still not been answered.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-02T16:15:47.0033333+00:00
@Erik Magnusson

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

I understand that you would like to use Path-Based Routing to route traffic across two app service domains.

I built a similar environment with two IIS VMs, with the second backend Pool is configured to receive requests that are for "mydomain.com/bar".

I was able to get this working successfully using Path-based rules and "Override backend path".

From your verbatim, I am afraid you are referring to Path based rules and Override backend path synonymously.

Did you configure "Override backend path" in the backend HTTP Settings of the AppGateway Rule?

If so, what value have you configured in the "Override backend path"?

Please let me know about the above.

Cheers,

Kapil
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-03T13:09:26.6833333+00:00

@Erik Magnusson

Could you please provide an update on this post?

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

Thanks,

Kapil
Erik Magnusson 45 Reputation points

2023-03-06T10:31:41.6133333+00:00

@KapilAnanth-MSFT

Thank you for your answer and sorry for the delay.

My intention was not to claim that bath-based routing and override backend path are synonymous. Essentially what I want to do is to set up a path-based routing and have the backend app service receive requests for its root path rather than the relative path indicated by the path-based rule.

I have used "/" as the override backend path value. My understanding is that this means the gateway would listen to requests for mydomain.com/bar and forward it to bar.azurewebsites.net. However, this is not happening. Instead, the requests are forwarded to foo.azurewebsites.net.

Thanks.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-06T13:44:21.1+00:00
@Erik Magnusson

Yes, your understanding is correct.

The combination of Path-based route and override backend path value as "/" should redirect mydomain.com/bar to bar.azurewebsites.net*

However, I am not able to repo the issue.

I have setup a similar environment and it is working as documented.

AppGw URL : http://www.contoso.com:8080

Accessing App1

AppGateway default (goes to App1)

Accessing App2

via App Gateway (fabrikam* - goes to App2)

App service 2

Accessing Subfolder in App2

via AppGw

App service 2

I would suggest you to check the configuration once again

Can you check if the behavior is same with HTTP (without TLS)?

Please check if "Pick host name from backend target" is enabled in backend HTTP Settings.

Can you also check the AccessLogs and check the parameters,
"originalRequestUriWithArgs_s" and "requestUri_s" ?

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-06T13:58:37.24+00:00

Hello @KapilAnanth-MSFT

Thank you for your quick answer!

The first request I make does seem to route me correctly to bar.azurewebsites.net. However, it's any subsequent, relative requests that cause problems. For example, no css files are loaded since the request is made to mydomain.com/style.css instead of mydomain.com/bar/styles.css. Since the first request will lead to foo.azurewebsites.net it won't find it since the file is obviously not there. The same goes for relative paths like /login.

"Pick host name from backend target" is enabled in backend HTTP Settings. I will check the rest of the configuration options you mentioned as well as setting up a test environment similar to yours to see if I get different results.

Thank you again.

Erik.
Erik Magnusson 45 Reputation points

2023-03-06T13:58:39.2033333+00:00

Hello @KapilAnanth-MSFT

Thank you for your quick answer!

The first request I make does seem to route me correctly to bar.azurewebsites.net. However, it's any subsequent, relative requests that cause problems. For example, no css files are loaded since the request is made to mydomain.com/style.css instead of mydomain.com/bar/styles.css. Since the first request will lead to foo.azurewebsites.net it won't find it since the file is obviously not there. The same goes for relative paths like /login.

"Pick host name from backend target" is enabled in backend HTTP Settings. I will check the rest of the configuration options you mentioned as well as setting up a test environment similar to yours to see if I get different results.

Thank you again.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-07T09:02:16.9033333+00:00
@Erik Magnusson

I wish you had told this earlier.

The issue is that "subsequent" requests, while using a Path based Rule does not work

I went ahead and configured my WebApp2 to have multiple pages.

Even here, I am not able to reproduce this error.

My webapp now has 3 pages, Page1(index), Page2 and CSS file.

When I access index page, CSS file loads properly

From index, I am successfully able to navigate to Page2

And also, from Page2, I am able to move back to index and forth

All this, without any change in the URL.

And I was using relative path

1.Accessing Index via AppGw

2.Going to Page2

3.Going back to Index

Next Steps:

Please check the AccessLogs for the parameters, "originalRequestUriWithArgs_s" and "requestUri_s" ?

One thing I do not understand is why the subsequent requests would go to mydomain.com/style.css instead of mydomain.com/bar/styles.css

Shouldn't the requests go to mydomain.com/bar/styles.css. In my case, (the "/fabrikam" part is not removed and is always there in the address bar)

Is the "/bar" from the URL getting removed once the first page loads from the address bar?

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-08T08:25:13.9533333+00:00

@KapilAnanth-MSFT

I apologize for being unclear in my original post. At the time, I was under the impression that the problem was of another character than it turned out to be. However, I have now managed to isolate the problem.

It arises as a result of the usage of the ~ sign in links, which in ASP.NET refers to the web root. Since the virtual path is "/", this is assumed to be the root, even if I publish in a sub directory like "/bar". The app will only recognize "/bar" as the root if I create an extra virtual path under that name. This, however, means that I will need two virtual paths in the same app and one of them, the "/" path, will point nowhere (since it can't be removed or changed). Also, overriding backend path is impossible in this case.

Another way would be to change every link across all projects to include their correct sub path, which is something I am hesitant to do for obvious reasons. In ASP.NET Core I can make use of the "base href"-element to accomplish this, but this option does not seem available in classic ASP.NET.

What I want to do is to have a sub folder recognized as web root without having to specify a virtual path under the same name, i.e. I want the path "/" to point to the application in "site\wwwroot\bar" and for this folder to be assigned as web root. Is this at all possible?

Thanks.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-08T09:29:38.4966667+00:00

@Erik Magnusson

I am glad you were able to isolate and mitigate the configuration.

I am afraid my expertise is with Azure Networking Products (AppGw, in this case) and have limited knowledge on App Services.

I would suggest you to create a new thread with the "Azure App Service" tag and the experts across community and Microsoft can shed some light on the sub folder question you have.

I shall now summarize our discussion and post it as an answer for a better reach across the community. I would highly appreciate if you could accept and upvote the same

Please let us know if I can be of further assistance here, I shall be glad to help as always :)

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-08T12:29:49.56+00:00

Thank you for your help! I will create a new thread concerning app services specifically.

Erik.

Accepted answer

0 additional answers

Your answer

Priya Kumar 1,096 Reputation points Microsoft Employee

2023-03-02T14:13:01.0633333+00:00

Hello @Eric Magnusson

Thanks for reaching Q&A platform.

Would like to explain you the understanding about the “Path Based Routing” and “override backend path”.

· When the HTTP setting is attached to a basic request-routing rule:

|Original
request|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | |/home/|/override/|/override/home/| |/home/secondhome/|/override/|/override/home/secondhome/|

· When the HTTP setting is attached to a path-based request-routing rule:

|Original
request|Path rule|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | -------- | |/pathrule/home/|/pathrule*|/override/|/override/home/| |/pathrule/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/home/|/pathrule*|/override/|/override/home/| |/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/pathrule/home/|/pathrule/home*|/override/|/override/| |/pathrule/home/secondhome/|/pathrule/home*|/override/|/override/secondhome/| |/pathrule/|/pathrule/|/override/|/override/|

Document: https://learn.microsoft.com/en-us/azure/application-gateway/configuration-http-settings#override-backend-path

Please elaborate the issue, if your query is still not been answered.
Priya Kumar 1,096 Reputation points Microsoft Employee

2023-03-02T14:13:20.08+00:00

Hello @Eric Magnusson

Thanks for reaching Q&A platform.

Would like to explain you the understanding about the “Path Based Routing” and “override backend path”.

· When the HTTP setting is attached to a basic request-routing rule:

|Original
request|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | |/home/|/override/|/override/home/| |/home/secondhome/|/override/|/override/home/secondhome/|

· When the HTTP setting is attached to a path-based request-routing rule:

|Original
request|Path rule|Override
backend path|Request
forwarded to back end| | -------- | -------- | -------- | -------- | |/pathrule/home/|/pathrule*|/override/|/override/home/| |/pathrule/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/home/|/pathrule*|/override/|/override/home/| |/home/secondhome/|/pathrule*|/override/|/override/home/secondhome/| |/pathrule/home/|/pathrule/home*|/override/|/override/| |/pathrule/home/secondhome/|/pathrule/home*|/override/|/override/secondhome/| |/pathrule/|/pathrule/|/override/|/override/|

Document: https://learn.microsoft.com/en-us/azure/application-gateway/configuration-http-settings#override-backend-path

Please elaborate the issue, if your query is still not been answered.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-02T16:15:47.0033333+00:00

@Erik Magnusson

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

I understand that you would like to use Path-Based Routing to route traffic across two app service domains.

I built a similar environment with two IIS VMs, with the second backend Pool is configured to receive requests that are for "mydomain.com/bar".

I was able to get this working successfully using Path-based rules and "Override backend path".

From your verbatim, I am afraid you are referring to Path based rules and Override backend path synonymously.

Did you configure "Override backend path" in the backend HTTP Settings of the AppGateway Rule?

If so, what value have you configured in the "Override backend path"?

Please let me know about the above.

Cheers,

Kapil
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-03T13:09:26.6833333+00:00

@Erik Magnusson

Could you please provide an update on this post?

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

Thanks,

Kapil
Erik Magnusson 45 Reputation points

2023-03-06T10:31:41.6133333+00:00

@KapilAnanth-MSFT

Thank you for your answer and sorry for the delay.

My intention was not to claim that bath-based routing and override backend path are synonymous. Essentially what I want to do is to set up a path-based routing and have the backend app service receive requests for its root path rather than the relative path indicated by the path-based rule.

I have used "/" as the override backend path value. My understanding is that this means the gateway would listen to requests for mydomain.com/bar and forward it to bar.azurewebsites.net. However, this is not happening. Instead, the requests are forwarded to foo.azurewebsites.net.

Thanks.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-06T13:44:21.1+00:00

@Erik Magnusson

Yes, your understanding is correct.

The combination of Path-based route and override backend path value as "/" should redirect mydomain.com/bar to bar.azurewebsites.net*

However, I am not able to repo the issue.

I have setup a similar environment and it is working as documented.

AppGw URL : http://www.contoso.com:8080

Accessing App1

AppGateway default (goes to App1)

Accessing App2

via App Gateway (fabrikam* - goes to App2)

App service 2

Accessing Subfolder in App2

via AppGw

App service 2

I would suggest you to check the configuration once again

Can you check if the behavior is same with HTTP (without TLS)?

Please check if "Pick host name from backend target" is enabled in backend HTTP Settings.

Can you also check the AccessLogs and check the parameters,
"originalRequestUriWithArgs_s" and "requestUri_s" ?

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-06T13:58:37.24+00:00

Hello @KapilAnanth-MSFT

Thank you for your quick answer!

The first request I make does seem to route me correctly to bar.azurewebsites.net. However, it's any subsequent, relative requests that cause problems. For example, no css files are loaded since the request is made to mydomain.com/style.css instead of mydomain.com/bar/styles.css. Since the first request will lead to foo.azurewebsites.net it won't find it since the file is obviously not there. The same goes for relative paths like /login.

"Pick host name from backend target" is enabled in backend HTTP Settings. I will check the rest of the configuration options you mentioned as well as setting up a test environment similar to yours to see if I get different results.

Thank you again.

Erik.
Erik Magnusson 45 Reputation points

2023-03-06T13:58:39.2033333+00:00

Hello @KapilAnanth-MSFT

Thank you for your quick answer!

The first request I make does seem to route me correctly to bar.azurewebsites.net. However, it's any subsequent, relative requests that cause problems. For example, no css files are loaded since the request is made to mydomain.com/style.css instead of mydomain.com/bar/styles.css. Since the first request will lead to foo.azurewebsites.net it won't find it since the file is obviously not there. The same goes for relative paths like /login.

"Pick host name from backend target" is enabled in backend HTTP Settings. I will check the rest of the configuration options you mentioned as well as setting up a test environment similar to yours to see if I get different results.

Thank you again.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-07T09:02:16.9033333+00:00

@Erik Magnusson

I wish you had told this earlier.

The issue is that "subsequent" requests, while using a Path based Rule does not work

I went ahead and configured my WebApp2 to have multiple pages.

Even here, I am not able to reproduce this error.

My webapp now has 3 pages, Page1(index), Page2 and CSS file.

When I access index page, CSS file loads properly

From index, I am successfully able to navigate to Page2

And also, from Page2, I am able to move back to index and forth

All this, without any change in the URL.

And I was using relative path

1.Accessing Index via AppGw

2.Going to Page2

3.Going back to Index

Next Steps:

Please check the AccessLogs for the parameters, "originalRequestUriWithArgs_s" and "requestUri_s" ?

One thing I do not understand is why the subsequent requests would go to mydomain.com/style.css instead of mydomain.com/bar/styles.css

Shouldn't the requests go to mydomain.com/bar/styles.css. In my case, (the "/fabrikam" part is not removed and is always there in the address bar)

Is the "/bar" from the URL getting removed once the first page loads from the address bar?

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-08T08:25:13.9533333+00:00

@KapilAnanth-MSFT

I apologize for being unclear in my original post. At the time, I was under the impression that the problem was of another character than it turned out to be. However, I have now managed to isolate the problem.

It arises as a result of the usage of the ~ sign in links, which in ASP.NET refers to the web root. Since the virtual path is "/", this is assumed to be the root, even if I publish in a sub directory like "/bar". The app will only recognize "/bar" as the root if I create an extra virtual path under that name. This, however, means that I will need two virtual paths in the same app and one of them, the "/" path, will point nowhere (since it can't be removed or changed). Also, overriding backend path is impossible in this case.

Another way would be to change every link across all projects to include their correct sub path, which is something I am hesitant to do for obvious reasons. In ASP.NET Core I can make use of the "base href"-element to accomplish this, but this option does not seem available in classic ASP.NET.

What I want to do is to have a sub folder recognized as web root without having to specify a virtual path under the same name, i.e. I want the path "/" to point to the application in "site\wwwroot\bar" and for this folder to be assigned as web root. Is this at all possible?

Thanks.

Erik.
KapilAnanth-MSFT 49,536 Reputation points Microsoft Employee Moderator

2023-03-08T09:29:38.4966667+00:00

@Erik Magnusson

I am glad you were able to isolate and mitigate the configuration.

I am afraid my expertise is with Azure Networking Products (AppGw, in this case) and have limited knowledge on App Services.

I would suggest you to create a new thread with the "Azure App Service" tag and the experts across community and Microsoft can shed some light on the sub folder question you have.

I shall now summarize our discussion and post it as an answer for a better reach across the community. I would highly appreciate if you could accept and upvote the same

Please let us know if I can be of further assistance here, I shall be glad to help as always :)

Cheers,

Kapil
Erik Magnusson 45 Reputation points

2023-03-08T12:29:49.56+00:00

Thank you for your help! I will create a new thread concerning app services specifically.

Erik.

Answer 1

@Erik Magnusson

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

I understand that you would like to use Path-Based Routing to route traffic across two app service domains.

Your requirement is that,

Request for mydomain.com/bar -> Redirected to bar.azurewebsites.net
Request for mydomain.com/bar/login -> Redirected to bar.azurewebsites.net/login
Request for mydomain.com/bar/site.css -> Redirected to bar.azurewebsites.net/site.css

The combination of Path-based route and override backend path value as "/" should redirect mydomain.com/bar to bar.azurewebsites.net*

The issue is that "subsequent" requests, while using a Path based Rule does not work and are going to "foo.azurewebsites.net"

I tried to repo this in my lab using JAVA WebApps, however, I am not able to repo the issue.

Later, you confirmed this is because of "~" sign in links, which in ASP.NET refers to the web root and also informed you were able to resolve this.

Since the virtual path is "/", this is assumed to be the root, even if we publish in a sub directory like "/bar". The app will only recognize "/bar" as the root if you create an extra virtual path under that name. This, however, means that you will need two virtual paths in the same app and one of them, the "/" path, will point nowhere (since it can't be removed or changed).

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

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.

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Override backend path not working as expected

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