If an assignment has many large submissions, use of the "Download all submissions" feature in mod_assign can cause high system load, and severely affect system performance (appears to be worse with load-balanced servers using round-robin).

As creating the zip files can take a long time, the user may become impatient and click the link more than once. This causes multiple partial zip files to be created in dataroot/temp, rapidly filling disk space

rob@MoodleWeb1pp:/var/www/moodle-data/temp$ ls -lh assignment_*
rw------ 1 www-data www-data 0 Jan 22 15:34 assignment_7oJUKn
rw------ 1 www-data www-data 669M Jan 22 15:38 assignment_7oJUKn.OiwJ4T
rw------ 1 www-data www-data 2.8G Jan 22 15:52 assignment_7oJUKn.tXoNJJ
rw------ 1 www-data www-data 0 Jan 22 15:51 assignment_Ayq4Kh
rw------ 1 www-data www-data 662M Jan 22 15:52 assignment_Ayq4Kh.Ar6CQZ
rw------ 1 www-data www-data 71M Jan 22 15:52 assignment_Ayq4Kh.cargSW
rw------ 1 www-data www-data 0 Jan 22 15:47 assignment_fRR4xX
rw------ 1 www-data www-data 663M Jan 22 15:51 assignment_fRR4xX.6XQ2It
rw------ 1 www-data www-data 742M Jan 22 15:52 assignment_fRR4xX.KAmfpb
rw------ 1 www-data www-data 0 Jan 22 15:38 assignment_Ki518s
rw------ 1 www-data www-data 669M Jan 22 15:47 assignment_Ki518s.RVRyBm
rw------ 1 www-data www-data 354M Jan 22 15:50 assignment_Ki518s.XlU2B9
rw------ 1 www-data www-data 0 Jan 22 15:29 assignment_wrkSjO
rw------ 1 www-data www-data 647M Jan 22 15:30 assignment_wrkSjO.aMiyAs
rw------ 1 www-data www-data 7.1G Jan 22 15:50 assignment_wrkSjO.wAsdQZ

Two possible way to mitigate this:

• add a check on the aggregate file size for all submissions to an assignment, and cancel the download if this exceeds a configurable limit (notifying the user to
• set a flag in the user's session while a download is running, and update code to ignore further download requests if the link is clicked again.