I've noticed this one issue that occurs on multiple DSpace instances running (4.x/5.x). When I take a look in the log folder I noticed that there are a number of solr log files which are missing.
I took at the Tomcat logs and I can see a reason why they are missing:
log4j:ERROR Unable to delete log file
log4j:ERROR Failed to rename [/opt/dspace/log/solr.log] to [/opt/dspace/log/solr.log.2015-07-13].
So it looks like it's failing to rotate.
This issue is quite common from what I can tell. For example looking back I can see may about 5 solr log files in the last 3 months.
I noticed that there are two places which write to solr.log.
Both of these files use different appenders
I noticed none of the other DSpace logs are getting lost such as dspace.log, cocoon.log etc. So I was wondering if it was related to having two appenders writing to the same file or if file size played any role in it.
From testing on a development environment I ruled out file size was an issue.
The next point I did was to remove the duplicate definitions so I removed it from log4j.properties (since log4j-solr.properties is required). The issue was still occurring.
What I did next was I took both file appenders and had them write to different log files so I could rule out if it was related to writing to the same file or it may help pinpoint which appender was failing to rotate.
As my assumption is that the appender that is used by log4j-solr.properties may be the issue here since all the other DSpace log files are working perfectly using the custom DSpace file appender.
So I had log4j.properties writing to solr.log and I had log4j-solr.properties writing to solr-standalone.log.
By making this change I could actually see that it wasn't failing as much. However the issue was still occurring and it only occurs with the solr-standalone.log file which makes me believe it is something to do with the file appender that log4j-solr.properties is using.
I'd be interested to hear if anyone else has seen this issue?
I'm currently still investigating the issue.