Confluence migrator produces tomcat temporary files that pile up and consume the storage capacity

[Enygma2002]

I've noticed this a couple of times in the past as well. After a migration (successful or not), the storage space was being held unnecessarily by tomcat temporary files produced during the confluence migrator operation.

Here is a sample of such files (folders, actually):

root@<redacted>:/var/cache/tomcat9/Catalina/localhost/xwiki/xwiki-temp# du -sh ./* | sort -h
4.0K    ./attachment-cache
4.0K    ./fileuploads
4.0K    ./mail
4.0K    ./svg
8.0K    ./confluencexml11381264652467701880
260K    ./cache
1.9M    ./extension
16M     ./confluencexml17131234034864176337
193M    ./confluencexml13588404071641817193
210M    ./confluencexml10474309618099928849
210M    ./confluencexml11286449192267968704
210M    ./confluencexml18169229049098535180

Sample of the folder contents/structure (in case it's useful for investigating):

root@<redacted>:/var/cache/tomcat9/Catalina/localhost/xwiki/xwiki-temp/confluencexml18169229049098535180# ls -al
total 15984
drwx------   4 tomcat tomcat     4096 Jul 28 15:05 .
drwxr-x---  14 tomcat tomcat     4096 Jul 29 11:49 ..
drwxr-x--- 113 tomcat tomcat     4096 Jul 28 15:05 attachments
-rw-r-----   1 tomcat tomcat 16346204 Jul 28 15:05 entities.xml
-rw-r-----   1 tomcat tomcat      665 Jul 28 15:05 exportDescriptor.properties
drwxr-x---   6 tomcat tomcat     4096 Jul 28 15:05 tree
root@<redacted>:/var/cache/tomcat9/Catalina/localhost/xwiki/xwiki-temp/confluencexml18169229049098535180# du -sh ./* | sort -h
4.0K    ./exportDescriptor.properties
16M     ./entities.xml
74M     ./attachments
121M    ./tree
root@<redacted>:/var/cache/tomcat9/Catalina/localhost/xwiki/xwiki-temp/confluencexml18169229049098535180/tree# du -sh ./* | sort -h
296K    ./spaces
1.1M    ./userimpls
22M     ./pages
98M     ./objects

I don't know the details of how the migrator works, but, ideally, these files should not live longer than they are actually required and should be immediately discarded to free up resources.

On a system with limited storage capacity (e.g. a demo instance), they can very quickly cripple the XWiki instance, not only the migration execution.

I have seen a relatively/similar issue on the product side that related to the Extension Manager creating tomcat temporary files: https://jira.xwiki.org/browse/XCOMMONS-2063 (could be useful or not).