Using WeBWorK LTI with Canvas

[lriddle]

We have been integrating WeBWorK as an external tool with Canvas via LTI. Students access their WeBWorK problem sets as a Canvas assignment, grade the problems in WeBWorK, then have the scores sent back to the Canvas gradebook. This was working fine until Saturday, May 16. On that day I was testing some WeBWorK problems for an upcoming summer course. Everything was going smoothly until that evening when all of a sudden WeBWorK started reporting that it was unsuccessful in sending the score to the LMS (i.e. Canvas). I believe this was because when WeBWorK tried to send the score to Canvas, it received the error message "Duplicate nonce detected". A problem I graded at 10:43 p.m. had the score successfully recorded in the Canvas gradebook. A problem I graded at 10:46 failed to have the score recorded in the Canvas gradebook. And every problem since then has not had the grade sent back to Canvas.

Has anyone else using Canvas and WeBWorK encountered a similar issue? Does anyone know how to fix this? We have tried contacting Canvas support but WeBWorK is not one of their "officially supported" external tools.

[lriddle · Accepted solution]

This issue has finally been resolved. Canvas was able to identify that our WeBWorK server was posting times that were more than 1 minute ahead of the timestamp Canvas had. Apparently Canvas only allows for 1 minute ahead and 5 minutes behind. After syncing the time on the WeBWorK server (as of today it was about 90 seconds ahead of the "official" time), I was able to grade a problem in WeBWorK and have the score successfully sent to the LMS. I guess on May 16 between 10:43 pm and 10:46 pm when grade feedback stopped working, our WW server's time must have crossed over the 1 minute ahead threshold.

[Stef_retired]

 @lriddle ‌

It was really thoughtful of you to take the time to come back here to share the solution! Thanks for being so helpful to your fellow community members, especially in these difficult times. Please check your direct messages for a small token of our appreciation. :0)

Thanks again for all that you do and keep up the good work!

Sincerely,

Canvas Community Team

[sarunas]

Hi,

We tried synchronizing our WeBWorK server time with either our local campus network NTP servers or with those from Ubuntu NTP pool (N.ubuntu.pool.ntp.org). We are still getting "Duplicate nonce detected" failures upon LTI grade passback. Failures are intermittent.

What time servers do you recommend to synchronize with?

Thank you,
Sarunas Burdulis (sarunas@math.dartmotuh.edu)
Dartmouth College