SharePoint passing the wrong SPAppWebUrl

Question

I'm seeing something weird happening in my provider hosted app. When deploying the app via Visual Studio, the output says:

App was installed at https://app-bebd3cad51d715.repsajapps.com/sites/devcenter/Test_PHApp/.

Okay, fine. So now I open up my SharePoint dev site, click on the app and my app is opened. But... the JSOM calls I put in there are failing. I started bugfixing and found out that the URL to my app looks like this:

https://testapp.repsajweb.com/?SPHostUrl=https%3A%2F%2Fportal%2Erepsajdev%2Ecom%2Fsites%2Fdevcenter&SPLanguage=en%2DUS&SPClientTag=0&SPProductNumber=15%2E0%2E4641%2E1000&SPAppWebUrl=https%3A%2F%2Fapp%2Dcc98c8ad51d714%2Erepsajapps%2Ecom%2Fsites%2Fdevcenter%2FTest%5FPHApp

Let's take a closer look at that SPAppWebUrl querystring parameter and decode it:

https://app-cc98c8ad51d714.repsajapps.com/sites/devcenter/Test_PHApp

Hey... huh... it's a different one as where the app was originally deployed to? When browsing it, SharePoint says:

Cannot find site for request 'https://app-cc98c8ad51d715.repsajapps.com/_login/default.aspx?ReturnUrl=/sites/devcenter/Test_PHApp/_layouts/15/Authenticate.aspx?Source=%252Fsites%252Fdevcenter%252FTest%255FPHApp&Source=/sites/devcenter/Test_PHApp'.

Which seems legit since the app was deployed somewhere else.

So the question now is; why the heck would it include a different URL in the querystring, pointing to a site which does not exist?

Update: from the URL to the app, I got the app instance id. That can be used to retrieve the app instance using Get-SPAppInstance in Powershell. The instance has a AppWebFullUrl property which points to the correct URL (the one from VisualStudio).

Update 2: I removed and rebuilt my developer site, which didn't help. It seems the URL being used for the appweb changed, but it still point to a site which doesn't. I also tried a simple app from the MSDN examples, which behaves exactly the same. I then tried reprovisioning the subscription and app management service applications (removing the databases), which also did not make any difference.

Answer 1

Okay. After a LOT of trial & error, I finally found out the problem.

In my ULS logs, I noticed an error stating it could not find https://portal.repsajdev.com:11978/sites/devcenter. My AAM setup of SharePoint is as follows: I have a host header web app running at 443 (SSL) and port 11978. My named site collection was runnning at https://portal.repsajdev.com/sites/devcenter and http://portal.repsajdev.com:11978/sites/devcenter. Notice a subtle difference; SharePoint was looking for https at port 11978, whilst I was running http. So the error was correct: that site didn't exist.

WHY it was searching for that URL, I have no clue. I smells like a bug, but I'm not 100% sure of that. The fix was rather simple; I changed my mapping to include an additional https endpoint on port 117979 at which I could run https://portal.repsajdev.com:11979/sites/devcenter. After redeploying my app, things magically started to work.

So whilst I still have a hard time explaining what went wrong here, I do have it fixed. Hope this might help someone in the future.