Thanks for the information. Why maintenance - as the log files get rolled daily, the old ones will be moved or deleted, in which case sincedb will have inode entries for files that don't exist anymore. Also any new log file may get created using same inode number of a deleted/moved file, therefore getting ignored by Logstash due to the presence of inode number in sincedb.
If Logstash overwrites the entire sincedb file with a in memory snapshot, its going to cause real issues for me.