Perl and BerkleyDB
In our Mailservers (Postfix) we use a lot of policy-servers, which are custom perl servers, eg granting sender permissions to external mailservers or building live-statistics of mail throughput. However, i recently ran into some problems starting one of those which uses a berkley database backend (aka bdb via BerkleyDB and BerkeleyDB::Env with DB_INIT_MPOOL from CPAN). On manual starting, i always got “Lock table is out of available locker entries”, which could not really be the case, because the perl-policy-server was the one and only accessing this database and the server has just been setup – so no traffic, a single newborn thread. Checking with db_stat revealed that bdb really thinks, all locks are in use:
1025 Last allocated locker ID 0x7fffffff Current maximum unused locker ID 5 Number of lock modes 1000 Maximum number of locks possible 1000 Maximum number of lockers possible 1000 Maximum number of lock objects possible 500 Number of current locks 501 Maximum number of locks at any one time 1000 Number of current lockers 1000 Maximum number of lockers at any one time 33 Number of current lock objects 34 Maximum number of lock objects at any one time 1504 Total number of locks requested 1004 Total number of locks released 0 Total number of locks upgraded 1000 Total number of locks downgraded 0 Lock requests not available due to conflicts, for which we waited 0 Lock requests not available due to conflicts, for which we did not wait 0 Number of deadlocks 0 Lock timeout value 0 Number of locks that have timed out 0 Transaction timeout value 0 Number of transactions that have timed out 712KB The size of the lock region 0 The number of region locks that required waiting (0%)
Well, the solution was to clear the environment directory on restart, because the statistics are (of course) persistent! So i removed any “__db.*”-file in the environment directory and everything worked like a charm again.