Something interesting I have noticed today, after running my huge single index (49 mio. records / 137 GB index) for about a week and replicating today I recognized that the heap usage after replication did not go down as expected. Expected means if solr is started I have a heap size between 4 to 5 GB and during the week under heavy load it might go up to 10 GB. But after replication in offline mode it recovers to between 5 to 6 GB. But today it was not going under 8 GB, even with forced GC from jvisualvm. So I first dropped the caches and tried again, no success. Next I turned off swap which took quite a while and turned it back on. This forced all content from swap back into memory. After calling Perform GC from jvisualvm the heap dropped below 5 GB. Bingo!
This leads me to the conclusion that java GC is not "seeing" or "reaching" objects which are located in swap. Anyone else seen this? As I am not short on memory or have any other problems I don't need any solution, but if there are some users having memory problems with old objects in swap I would suggest a cronjob after replication with swapoff/swapon and GC afterwards. Bernd
