I'ts been 10 days since I migrated about 400 user accounts from our previous Zimbra 9 server to a fresh Carbonio installation. Since the migration was completed and the server online, I've noticed that the thread count for the server has started increasing. In just a week it has grown (almost linearly) from under 1000 to more than 3000 threads, And I don't know how to stop it and where will it reach. 

Further investigation let me see that it has something to do with /usr/share/carbonio/carbonio-tasks.jar. It seems that those processes never stop.

running ps auxH lists right now more than 1500 identical lines with this data about the threads running:

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
carboni+ 6411 0.0 4.1 9406808 1354964 ? Sl Aug19 0:00 /opt/zextras/common/bin/java -Djava.net.preferIPv4Stack=true -Xms1024m -Xmx2048m -DTASKS_LOG_LEVEL=warn -jar /usr/share/carbonio/carbonio-tasks.jar

 The only difference between them is the start time of each one. There are about 200 threads launched everyday, and they remain there. But all have the same PID,VSZ, RSS 

A temporary solution I've found is to restart the carbonio-tasks service

service carbonio-tasks restart

That way the number of threads has decreased to a much more reasonable amount, and carbonio-tasks.jar threads are only 39 right now. 

Is there something I can do to solve this issue, some setting that I'm missing?

Thanks a lot for your help