The Assignments List shows the progress of each assignment. This is a very useful feature, but also a very expensive one in terms of server resources required.

To prevent it from conflicting with more urgent needs such as actually running the quizzes, we updated the progress bars only once per day, in the middle of the night when the servers were not otherwise busy. This worked well, but it reduced the utility somewhat.

We have now moved the updating routine into a queuing system called Celery (no idea why!), which tracks actual server load and slots little bits of low-priority tasks into the gaps when the CPUs are not busy.

I’m really pleased with the results. Except perhaps at very busy times, updating appears instant.