How do I get my app working?

[phesse]

I am an administrator of Canvas at my college, and I have an issue with getting an app to work in Canvas.

The essence of my project is to display an external web page within Canvas. After going through the tutorials and reading the documentation, and with help from others, I was able to get the app set up. I created the xml configuration file and stored it on our public-facing server along with the webpage (it's for taking attendance). I created the app and that seemed to work, but when I click on it, I get an empty page. Nothing is displayed.

I first thought the problem was related to the documentation that states the webpage to display must be displayable in an iframe. I found a solution on google which involved creating a web.config file in the same folder as the webpage, with code to make the page displayable. This didn't work. I could not even display the webpage in a browser.

Can someone help? I would think this would have been done before by someone. I've been told that Canvas's attendance system is pretty basic, so it follows that some customers would need to bring their external attendance system into Canvas seamlessly.

Any help would be much appreciated.

[kona]

I'm sure of the answer to this question, but I'm going to share it with the Canvas Developers​ group in the Community to see if they can help.

[tdelillo]

 @phesse ​ - While this may be an issue with the app setup, when I see the words "empty page", my first thought is browser security issue. The "Browser Privacy Settings" section of the Which browsers does Canvas support?​ document will tell you how to determine if your content is being blocked by the browser.

[phesse]

Thanks Tracey. I checked my browser (Chrome) and it's the right version.

More information: In the developer console I got the message "Refused to display <the webpage> in a frame because it set X-Frame-Options to SAMEORIGIN". I found that there's a setting in IIS that sets X-Frame-Options (HTTP Response Headers section). By default (i.e. if the setting isn't in there) the option is set to SAMEORIGIN. I added the setting and set it to ALLOW-FROM https://Dunwoody/instructure/com, re-created the app and tried it again. This time I got the error "The page cannot be displayed because and internal server error has occurred." In the developer console, the message is "POST...500 (Internal Server Error)." I tried accessing the page in my browser and get the error message "Failed to load resource: the server responded with a status of 500 (internal server error).

Hope this helps. I'm still digging on my end but please pass along any help you can provide.

[garth]

LTI apps must be hosted using HTTPS.

Are you using HTTPS, or only HTTP?

[phesse]

I'm using HTTPS

[phesse]

Update:

The previous test I described above was done on our production server. Today we were able to get our test server public-facing, so we could run the test again. This time it worked - the webpage displayed in the iframe in Canvas. However, the following message was displayed in the developer console in Chrome: "Invalid x-frame-options header encountered when loading https://...'Allow from https://dunwoody.instructure.com' is not a recognized directive. The header will be ignored." Has anyone seen this error before, and if so, is it something we should be concerned with?

My problem is still not resolved. The webpage won't display on our production server. Please let me know if you have any ideas.

[garth]

I woudl start by comparing the web server and application configuration between your dev server and your production server.

What is the difference, besides the URL?

Do you have your dev URL hardcoded somewhere in your app that could be causing trouble?

Is your LTI XML file referencing the correct URL?

[Robbie_Grant]

 @phesse ,

We are giving the Canvas Admins area a little bit of love (especially questions that are really, really old) and just want to check in with you.  This will also bring this question new attention. 

Were you able to find an answer to your question? I am going to go ahead and mark this question as answered because there hasn't been any more activity in a while so I assume that you have the information that you need. If you still have a question about this or if you have information that you would like to share with the community, by all means, please do come back and leave a comment.  Also, if this question has been answered by one of the previous replies, please feel free to mark that answer as correct.

Robbie

[phesse]

Yes you can mark it answered. It was one of those cases where it solved itself I suspect. The problem just stopped occurring after a while.

Thanks for checking in.

Pete

Pete Hesse

Programmer/Database Analyst

Dunwoody College of Technology

Direct: 612.381.3397

phesse@dunwoody.edu<mailto:phesse@dunwoody.edu>