maps fills up /tmp with temporary image files

[dirks]

Steps to reproduce

• Enable the maps application on an nextcloud instance
• Have smb storages mounted via nextcloud external storage that has many images

Expected behaviour:

• maps does not create copies of images in /tmp file system
• maps does not fill the /tmp file system

Actual behaviour:

• in /tmp many oc_tmp_*-.JPG, oc_tmp_*-.tif files and empty oc_tmp_* files are created which eventually fill up /tmp
• the files are deleted after some time and a new set of files is created
• in our monitoring we observe a saw tooth pattern like this
• when disabling maps the saw tooth pattern stops. The last block in the graph is after disabling maps followed by manual deletion of the files after a grace period (shouldn't the app clean up when it disabled?).

If your /tmp partition is not separate from / this leads to problems (e.g. redis can not write back to disk). As a workaround I created a separate /tmp partition with 10 GB, this is what you see in the monitoring, before the root file system was used, which had ~4 GB of free space which were then filled by oc_tmp* files.

I do not know why the files are copied and deleted again shortly after. My guess is, this is connected to external smb shares since I saw a lot of traffic from the smb server to the nextcloud instance, but it might be unrelated.

Also, this instance has some memory available (12 GB of memory of which 5 to 10 GB where available all the time), which could have been used, but instead the files were written out to disk.

Server configuration

• Ubuntu 18.04
• Apache 2.4.29
• postgresql 10
• php 7.2
• nextcloud 18.0.7.1

Server is behind (apache) reverse proxy with ssl offloading.

Please let me know if you need additional information.

[tacruc]

I think there is not much we can do, except adding an option to ignoring the smb file system.