I use Rails’ database session backend for LM. (for login, as well as “flash”) Without any sort of built in garbage collection the sessions table gets very large, very quickly. Beyond aesthetic issues, this can also cause MySQL’s key buffer to fill up. (which on Debian is by default set quite low)
So I wrote up a quick flush method, and saved it in a file
class CGI::Session::ActiveRecordStore::Session def self.flush_old_empty_sessions self.delete_all "DATE_SUB(NOW(),INTERVAL 6 HOUR) > updated_at and BIT_LENGTH(data) <= 688" end end
This says nuke all sessions which are over 6 hours old, and which are empty. (688 is the length of the serialized session with an empty flash)
MySQL specific, and susceptible to changes in either session structure or its serialization. But it was quick and easy and worked for me.
Then you simply need a cron job like:
ruby script/runner 'CGI::Session::ActiveRecordStore::Session.flush_old_empty_sessions'