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LTI pass back grades to Blackboard

by Bianca Sosnovski -
Number of replies: 7

Hi everyone,

We reinstalled our Webwork server from scratch in the fall and added a SSL Certificate too. After these changes our LTI connection with Blackboard stopped passing back the grades to Blackboard, though login was still possible using a LTI link.

After looking around the system, we found out that the problem was with the handshake between the systems. It seems Blackboard had a weaker security key. The university just updated the systems and now Webwork is passing back  the grades again to Blackboard. But the following warning message always appear when a user submit an answer for a problem in an assignment for the first time and then it doesn't show no more.

Anyone has any idea what is causing this???

"WeBWorK Warnings

WeBWorK has encountered warnings while processing your request. If this occured when viewing a problem, it was likely caused by an error or ambiguity in that problem. Otherwise, it may indicate a problem with the WeBWorK system itself. If you are a student, report these warnings to your professor to have them corrected. If you are a professor, please consult the warning output below for more information.

Warning messages

• Argument "success" isn't numeric in subtraction (-) at /opt/webwork/webwork2/lib/WeBWorK/Authen/LTIAdvanced/SubmitGrade.pm line 337."

Thanks.

Re: LTI pass back grades to Blackboard

by Nathan Wallach -

Due to all the various debug versions of SubmitGrade.pm posted in the forums - it is hard for me to be certain what exact version you have installed.

If line 337 of your file is:

if ($oldScore ne "" && abs($score-$oldScore) < 0.001) { I suggest trying to change it to if ($oldScore ne "" && $oldScore ne "success" && abs($score-$oldScore) < 0.001) { which may solve the problem. Several lines before, the value of$oldScore is set, and apparently in certain circumstances the value obtained is the string "success" which should not be used in the numerical calculation at the end of the list of tests.

If that is not line 337 of your file, please send the file as an attachment in the forum so I can look at it.

Re: LTI pass back grades to Blackboard

by Bianca Sosnovski -
Hi Nathan,

Definitely, what you wrote is not what is in our SubmitGrade.pm file. The version of the file we have currently in our server is attached.

Thanks.

Re: LTI pass back grades to Blackboard

by Nathan Wallach -

I'm stumped.

The version of SubmitGrade.pm you sent seems to be the standard version in WW 2.15, and I cannot think of any reason why it would trigger the error message you reported.

The versions of SubmitGrade.pm which use a 2 stage process to avoid sending updates to the LMS when the grade did not change would have a subtraction to compare the old and new grades similar to what I sent you - and if the "success" string is appearing where a grade was expected on the first submission (before the LMS has a recorded grade) - that would seem to explain why the error could appear.

Are you certain that you looked at the file in the location where the server is taking the code from and not in a "clean" Git managed directory?

Re: LTI pass back grades to Blackboard

by Bianca Sosnovski -
Nathan,

Million apologies!! Sent you the incorrect file.
The spring semester didn't start yet but I'm already overwhelmed with work! I'm super tired 😔.

I had just switched the files in the server for the standard one in Webwork 2.15. The reason why I switched is that I remembered changed it to another version sometime ago to get a better error message with the issue I mentioned above in my original post here. I used a modified version as I mentioned in a reply to one of your posts here https://webwork.maa.org/moodle/mod/forum/discuss.php?d=4770#p14184
(the modified file is attached below)

After I switched back to the standard version, I didn't restart the Apache server so the change didn't take place and it continues showing the warning message. Now that I have started the server, no more warning message with the standard file SubmitGrade.pm in version 2.15.

The SubmitGrade file that was show the warning is the below.

I really appreciate you time with this.Thanks a lot.

Re: LTI pass back grades to Blackboard

by Nathan Wallach -

That file also seems to be a "standard one" but the version in the forum chain is what I had expected it to be. The earlier suggested patch had a bug which is fixed in the file attached here. (We all get tired.)

I modified the version from that forum chain to hopefully fix the bug, as well as to make the 2-round process where WW checks the old LMS grade to determine if an update is needed optional.

The new file is attached, and has been tested on my server.

There is a new control setting to enable in the course.conf file (or system wide) to turn on the 2-round process:

• \$lti_check_prior = 1;
• It defaults to being off.

Re: LTI pass back grades to Blackboard

by Bianca Sosnovski -

Thank you so much!

Re: LTI pass back grades to Blackboard

by Bianca Sosnovski -
Hi Nathan,

I finally had the chance to test the new file SubmitGrade.pm above and it is working.
Thank you again.