NAME CHI::Driver::LMDB - use OpenLDAPs LMDB Key-Value store as a cache backend. VERSION version 0.001000 SYNOPSIS use CHI; my $cache = CHI->new( driver => 'LMDB', root_dir => 'some/path', namespace => "My::Project", ); See "CHI" documentation for more details on usage. ATTRIBUTES "dir_create_mode" What mode (if any) to use when creating "root_dir" if it does not exist. ->new( # Default is 775 = rwxr-xr-x dir_create_mode => oct 666, ); "root_dir" The prefix directory the "LMDB" data store will be installed to. ->new( root_dir => 'some/path' ) Default is: OSTEMPDIR/chi-driver-lmdb-$EUID "cache_size" The size in bytes for each database. This is a convenience wrapper for "mapsize" which supports suffixes: cache_size => 5 # 5 bytes cache_size => 5k # 5 Kilobytes cache_size => 5m # 5 Megabytes ( default ) This is also designed for syntax compatibility with "CHI::Driver::FastMmap" "single_txn" single_txn => 1 SPEED: For performance benefits, have a single transaction that lives from the creation of the CHI cache till its destruction. However, WARNING: this flag is currently a bit dodgy, and CHI caches being kept alive till global destruction WILL trigger a "SEGV", and potentially leave your cache broken. You can avoid this by manually destroying the cache with: undef $cache Prior to global destruction. "db_flags" Flags to pass to "OpenDB"/"LMDB_File->open". See "LMDB_File"'s constructor options for details. use LMDB_File qw( MDB_CREATE ); db_flags => MDB_CREATE # default "tx_flags" Flags to pass to "LMDB::Env->new" See "LMDB::Env"'s constructor options for details. Default is 0 tx_flags => 0 # no flags "put_flags" Flags to pass to "->put(k,v,WRITE_FLAGS)". See LMDB_File->put options for details. "mapsize" Passes through to "LMDB::Env->new( mapsize => ... )" Default value is taken from "cache_size" with some "m/k" math if its set. "maxreaders" TODO: Currently not defined due to rt#98821 Passes through to "LMDB::Env->new( maxreaders => ... )" "maxdbs" Passes through to "LMDB::Env->new( maxdbs => ... )" Defines how many CHI namespaces ( Databases ) a path can contain. Default is 1024. "mode" Passes through to "LMDB::Env->new( mode => ... )" Defines the permissions on created DB Objects. Defaults to "oct 600" == "-rw-------" "flags" Passes through to "LMDB::Env->new( flags => ... )" PERFORMANCE If write performance is a little slow for you ( due to the defaults being a single transaction per SET/GET operation, and transactions being flushed to disk when written ), there are two ways you can make performance a little speedy. Single Transaction Mode. If you pass "single_txn => 1" the cache will be given a single transaction for the life of its existence. However, pay attention to the warnings about cleaning up properly in "single_txn". Also, this mode is less ideal if you want to have two processes sharing a cache, because the data won't be visible on the other one till it exits! ☺ "NOSYNC" Mode. You can also tell LMDB NOT to call "sync" at the end of every transaction, and this will greatly improve write performance due to IO being greatly delayed. This greatly weakens the databases consistency, but that seems like a respectable compromise for a mere cache backend, where a missing record is a performance hit, not a loss of data. use LMDB_File qw( MDB_NOSYNC MDB_NOMETASYNC ); ... my $cache = CHI->new( ... flags => MDB_NOSYNC | MDB_NOMETASYNC ); This for me cuts down an operation that takes 30 seconds worth of writes down to 6 ☺. Comparison vs FastMmap FastMmap is still faster for reads. Here is a simple comparison for runs of my "dep_changes.pl" utility which does a respectable amount of cache look-ups. Google Docs Image For writes, whether or not FastMmap is faster depends on settings. * "NOSYNC" + "single_txn = 1" tends to give faster performance than "FastMmap". * "NOSYNC" + "single_txn = 0" gives comparable performance to "FastMmap" * "SYNC" + "single_txn = 1" tends to give slightly worse performance than "FastMmap" Google Docs Image However, * "SYNC" + "single_txn = 0" gives much worse performance than all of the above. Google Docs Image AUTHOR Kent Fredric COPYRIGHT AND LICENSE This software is copyright (c) 2014 by Kent Fredric . This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.