We have just come out of our exam period where we ran one campus based STACK based exam with all the students (~270) starting at the same time and most ending at the same time.
We experienced a number of performance issues which we are working through - mostly when all students hit begin at the start and submit at the end.
During the exam, a number of students complained of receiving autosave error messages (like this https://docs.moodle.org/311/en/Using_Quiz#/media/File:Quiz_disconnect.png). I'm trying to understand the behaviour of autosaving during STACK exams. Our autosave timing is set to every 1 minute. I see that the autosave behaviour is partly implemented here: https://github.com/moodle/moodle/blob/master/mod/quiz/yui/src/autosave/js/autosave.js, but this relates to timing triggers on the TINYMCE editor. STACK quizzes use simple HTML input fields for capturing student responses.
Can anyone shed light on the autosave behaviour within STACK questions? For example, is the autosave timing defaulting only to the master setting of every 1 minute (default period) OR is there some randomisation introduced to ensure all the student's browsers are not synced to autosave at the same time every minute thoughout the exam?
Our server monitoring showed moderate-low CPU stress during the exam (but very high peaks at start and end). I do not know if there were any local network issues at the time, but I have no evidence for it.
Any insights or advice appreciated.
Thanks,
Stuart