Gradebook not displaying correctly

[Jorge Herskovic]

Hi,

I have a course with a large number of students and a large number of assignments. When the instructor opens the gradebook, some rows known to have grades show up blank. If you click on the student's name, it shows the grades correctly. If you export the gradebook to CSV, it's filled out correctly. But I can't get the online version of the gradebook to display properly.

We're using the old gradebook, not the new one, FWIW.

Ideas very welcome.

Jorge Herskovic

MD Anderson Cancer Center

[Jorge Herskovic]

We're still seeing these problems at random. 

/api/v1/courses/[number]/students/submissions?[stuff] errors out while the gradebook is loading, which makes nginx return a 502-bad gateway, which stops the execution and renders the gradebook incomplete. 

Still trying to trace the error to actual Canvas code.

[Christopher Bennell]

Are you seeing the error in your error_reports page or nginx/apache/passenger logs?

[Jorge Herskovic]

Figured it out. I was able to find a concurrent message in the nginx error logs that pointed me in the right direction. It may be worth pointing out that we run Canvas under unicorn + nginx. And nginx is pretty strict about the size of the headers it receives from upstream.

Some grade entries were over the size of the accepted headers and made nginx return a 502. Why this happened only in the gradebook, only in certain courses, and only for certain submissions within those courses, I don't know.

In the end, adding

    fastcgi_buffers 16 16k;

    fastcgi_buffer_size 64k;

    proxy_buffer_size   128k;

    proxy_buffers   4 256k;

    proxy_busy_buffers_size   256k;

 to the http block of nginx.conf solved the problem. It's worth pointing out that just increasing the fastcgi buffer size, as one may expect, isn't enough. The proxy buffers need to be addressed too.

On Wednesday, June 20, 2018 at 2:30:14 PM UTC-5, Jorge Herskovic wrote: