Catalina.out在由bash脚本编辑后未记录

Question

This is a tomcat7 installation with the default logging configuration, the catalina.out is only being rolled out when we restart the server. As it is prod server we can not restart it very often. We have a huge number of entries going to that file which causes our catalina.out to grow very high in few days until it consumes the whole diskspace.

As we don't want to change the logging configuration as it is puppetized and we would need to create devops tickets and all that slow stuff, I wrote a bash script that is being run every 5 min via crontab that will cut the log file by half when a limit is reached, the script is like the following:

 if [ $catalinaSize -gt $catalinaThreshold ]; then
  middle=$(wc -l $catalinaLoc | awk '{ print $1 }')
  middle=$(( $middle / 2 ))
  sed -i -e 1,${middle}d $catalinaLoc
  echo "+++ catalina.out was cut by half"

Basically this script checks the current size of the file and compares it to a threshold value, then it uses wc and awk to retrieve the number of lines in that file so it can use then sed for cutting the file by half.

I tested the script in other environments and it worked. The problem is that after some successful runs for several days in production, suddenly the catalina.out is not getting any log entries from tomcat since some days ago.

The explanation I think about is that Tomcat is not able to write into that file anymore because of the cut by half operation.

Is it possible to know what is preventing Tomcat to write into that file?

Answer 1

I suspect it is sed -i doing the damage: behind the scenes, it writes the output stream to a temp file, then moves the temp file to the original name. I suspect the file handle held by catalina no longer points to any file.

You'll have to find a way to actually edit the file, not replace it. This might be a valid replacement for sed :

printf "%s\n" "1,${middle}d" "wq" | ed "$catalinaLoc"

Tangentially, an easier way to get the number of lines:

middle=$(( $(wc -l < "$catalinaLoc") / 2 ))

When you redirect to wc , it no longer prints out the filename.