Hey there, MLDBM::Sync is finally available in CPAN, also at: http://www.perl.com/CPAN-local/modules/by-module/MLDBM/ Below is a bit of the README... Its a locking wrapper around MLDBM I developed for the purpose of creating safe fast DBM storage for multi-process environments. DBM's like DB_File & SDBM_File can become corrupt if not properly locked and have their i/o flushed, though DB_File is much more sensitive to this. Further, there's a special wrapper around SDBM_File which gets around its 1024 byte limit, called MLDBM::Sync::SDBM_File, see benchmarks below. --Josh _________________________________________________________________ Joshua Chamas Chamas Enterprises Inc. NodeWorks >> free web link monitoring Huntington Beach, CA USA http://www.nodeworks.com 1-714-625-4051 NAME MLDBM::Sync (BETA) - safe concurrent access to MLDBM databases SYNOPSIS use MLDBM::Sync; # this gets the default, SDBM_File use MLDBM qw(DB_File Storable); # use Storable for serializing use MLDBM qw(MLDBM::Sync::SDBM_File); # use extended SDBM_File, handles values > 1024 bytes # NORMAL PROTECTED read/write with implicit locks per i/o request tie %cache, 'MLDBM::Sync' [..other DBM args..] or die $!; $cache{"AAAA"} = "BBBB"; my $value = $cache{"AAAA"}; # SERIALIZED PROTECTED read/write with explicity lock for both i/o requests my $sync_dbm_obj = tie %cache, 'MLDBM::Sync', '/tmp/syncdbm', O_CREAT|O_RDWR, 0640; $sync_dbm_obj->Lock; $cache{"AAAA"} = "BBBB"; my $value = $cache{"AAAA"}; $sync_dbm_obj->UnLock; DESCRIPTION This module wraps around the MLDBM interface, by handling concurrent access to MLDBM databases with file locking, and flushes i/o explicity per lock/unlock. The new Lock()/UnLock() API can be used to serialize requests logically and improve performance for bundled reads & writes. my $sync_dbm_obj = tie %cache, 'MLDBM::Sync', '/tmp/syncdbm', O_CREAT|O_RDWR, 0640; $sync_dbm_obj->Lock; ... all accesses to DBM LOCK_EX protected, and go to same file handles ... $sync_dbm_obj->UnLock; MLDBM continues to serve as the underlying OO layer that serializes complex data structures to be stored in the databases. See the MLDBM the BUGS manpage section for important limitations. BENCHMARKS In the distribution ./bench directory is a bench_sync.pl script that can benchmark using the various DBMs with MLDBM::Sync. The MLDBM::Sync::SDBM_File DBM is special because is uses SDBM_File for fast small inserts, but slows down linearly with the size of the data being inserted and read, with the speed matching that of GDBM_File & DB_File somewhere around 20,000 bytes. So for DBM key/value pairs up to 10000 bytes, you are likely better off with MLDBM::Sync::SDBM_File if you can afford the extra space it uses. At 20,000 bytes, time is a wash, and disk space is greater, so you might as well use DB_File or GDBM_File. Note that MLDBM::Sync::SDBM_File is ALPHA as of 2/27/2001. The results for a dual 450 linux 2.2.14, with a ext2 file system blocksize 4096 mounted async on a SCSI disk were as follows: === INSERT OF 50 BYTE RECORDS === Time for 100 write/read's for SDBM_File 0.12 seconds 12288 bytes Time for 100 write/read's for MLDBM::Sync::SDBM_File 0.14 seconds 12288 bytes Time for 100 write/read's for GDBM_File 2.07 seconds 18066 bytes Time for 100 write/read's for DB_File 2.48 seconds 20480 bytes === INSERT OF 500 BYTE RECORDS === Time for 100 write/read's for SDBM_File 0.21 seconds 658432 bytes Time for 100 write/read's for MLDBM::Sync::SDBM_File 0.51 seconds 135168 bytes Time for 100 write/read's for GDBM_File 2.29 seconds 63472 bytes Time for 100 write/read's for DB_File 2.44 seconds 114688 bytes === INSERT OF 5000 BYTE RECORDS === (skipping test for SDBM_File 1024 byte limit) Time for 100 write/read's for MLDBM::Sync::SDBM_File 1.30 seconds 2101248 bytes Time for 100 write/read's for GDBM_File 2.55 seconds 832400 bytes Time for 100 write/read's for DB_File 3.27 seconds 839680 bytes === INSERT OF 20000 BYTE RECORDS === (skipping test for SDBM_File 1024 byte limit) Time for 100 write/read's for MLDBM::Sync::SDBM_File 4.54 seconds 13162496 bytes Time for 100 write/read's for GDBM_File 5.39 seconds 2063912 bytes Time for 100 write/read's for DB_File 4.79 seconds 2068480 bytes === INSERT OF 50000 BYTE RECORDS === (skipping test for SDBM_File 1024 byte limit) Time for 100 write/read's for MLDBM::Sync::SDBM_File 12.29 seconds 16717824 bytes Time for 100 write/read's for GDBM_File 9.10 seconds 5337944 bytes Time for 100 write/read's for DB_File 11.97 seconds 5345280 bytes
