On Thu 29 Oct 2009, Mahesh Khambadkone wrote: > As it seldom changes, we dont want to use a database for these > 'config values', yet need a way to retain in memory and dirty its' > value from time to time.
Have a look at MMapDB which I have just uploaded to CPAN. I wrote this module some time ago exactly for that case: configuration data that seldom changes. Before I have used BerkeleyDB. But that is a bit touchy when it comes to sudden process death. I wanted something simple, stable and fast. So an MMapDB database cannot be modified by a connected process because it is mapped read-only. Changing data means rewriting the database file and reconnect the new one. This also means the whole database is shared memory between all connected processes. There is a tie() based interface. So, even dumping human readable data is simple: perl -MMMapDB -MData::Dumper -e ' print Dumper(MMapDB->new(filename=>shift)->start->main_index); ' /etc/opt/TRANSCONFIG/transconfig.mmdb And a more complicated but faster interface: perl -MMMapDB -le ' # open the DB my $db=MMapDB->new(filename=>shift)->start; # get data record positions my @pos=$db->index_lookup($db->mainidx, qw!actn opi /svn!); # fetch a data item print $db->data_record($pos[0])->[2]; ' /etc/opt/TRANSCONFIG/transconfig.mmdb One even can store large values there and pass references to them around and thus avoid copying and mallocing that happens normally when you do $x=$y: perl -MMMapDB -MDevel::Peek -e ' my $db=MMapDB->new(filename=>shift)->start; my @pos=$db->index_lookup($db->mainidx, qw!actn opi /svn!); # get a reference to the data item to avoid copying my $v=\$db->data_record($pos[0])->[2]; print $$v, "\n"; Dump $$v ' /etc/opt/TRANSCONFIG/transconfig.mmdb File: '/opt/svnbook'.$MATCHED_PATH_INFO SV = PV(0x9d4b50) at 0x7c9248 REFCNT = 1 FLAGS = (POK,READONLY,pPOK) PV = 0x7f956388d240 "File: '/opt/svnbook'.$MATCHED_PATH_INFO" CUR = 39 LEN = 0 You see $v points to a read-only variable. The PV pointer of this variable references the string inside the read-only mapped database file. Now you can do $x=$v and only the reference is copied. Torsten -- Need professional mod_perl support? Just hire me: torsten.foert...@gmx.net
