NAME

Bot::Cobalt::DB - Locking Berkeley DBs with serialization

SYNOPSIS

use Bot::Cobalt::DB;

## ... perhaps in a Cobalt_register ...
my $db_path = $core->var ."/MyDatabase.db";
my $db = Bot::Cobalt::DB->new(
  file => $db_path,
);

## Open (and lock):
$db->dbopen;

## Do some work:
$db->put( SomeKey => $some_deep_structure );

for my $key ($db->dbkeys) {
  my $this_hash = $db->get($key);
}

## Close and unlock:
$db->dbclose;

DESCRIPTION

Bot::Cobalt::DB provides a simple object-oriented interface to basic DB_File (Berkeley DB 1.x) usage.

BerkDB is a fast and simple key/value store. This module uses JSON to store nested Perl data structures, providing easy database-backed storage for Bot::Cobalt plugins.

Constructor

new() is used to create a new Bot::Cobalt::DB object representing your Berkeley DB:

my $db = Bot::Cobalt::DB->new(
  file => $path_to_db,

 ## Optional arguments:

  # Database file mode
  perms => $octal_mode,

  ## Locking timeout in seconds
  ## Defaults to 5s:
  timeout => 10,

  ## Normally, references are serialized transparently.
  ## If raw is enabled, no serialization filter is used and you're
  ## on your own.
  raw => 0,
);

Opening and closing

Database operations should be contained within a dbopen/dbclose:

## open, put, close:
$db->dbopen || croak "dbopen failure";
$db->put($key, $data);
$db->dbclose;

## open for read-only, read, close:
$db->dbopen(ro => 1) || croak "dbopen failure";
my $data = $db->get($key);
$db->dbclose;

Methods will fail if the DB is not open.

If the DB for this object is open when the object is DESTROY'd, Bot::Cobalt::DB will attempt to close it safely.

Locking

Proper locking is done -- that means the DB is 're-tied' after a lock is granted and state cannot change between database open and lock time.

The attempt to gain a lock will time out after five seconds (and "dbopen" will return boolean false).

The lock is cleared on "dbclose".

If the Bot::Cobalt::DB object is destroyed, it will attempt to dbclose for you, but it is good practice to keep track of your open/close calls and attempt to close as quickly as possible.

Methods

dbopen

dbopen opens and locks the database. If 'ro => 1' is specified, this is a LOCK_SH shared (read) lock; otherwise it is a LOCK_EX exclusive (write) lock.

Try to call a dbclose as quickly as possible to reduce locking contention.

dbopen() will return false (and possibly warn) if the database could not be opened (probably due to lock timeout).

is_open

Returns a boolean value representing whether or not the DB is currently open and locked.

dbclose

dbclose closes and unlocks the database.

put

The put method adds an entry to the database:

$db->put($key, $value);

The value can be any data structure serializable by JSON::MaybeXS.

Note that keys should be properly encoded:

my $key = "\x{263A}";
utf8::encode($key);
$db->put($key, $data);

get

The get method retrieves a (deserialized) key.

$db->put($key, { Some => 'hash' } );
## . . . later on . . .
my $ref = $db->get($key);

del

The del method removes a key from the database.

$db->del($key);

dbkeys

dbkeys will return a list of keys in list context, or the number of keys in the database in scalar context.

dbdump

You can serialize/export the entirety of the DB via dbdump.

## YAML::Syck
my $yamlified = $db->dbdump('YAML');
## YAML::XS
my $yamlified = $db->dbdump('YAMLXS');
## JSON::MaybeXS
my $jsonified = $db->dbdump('JSON');

See Bot::Cobalt::Serializer for more on freeze() and valid formats.

A tool called cobalt2-dbdump is available as a simple frontend to this functionality. See cobalt2-dbdump --help

FORMAT

Bot::Cobalt::DB databases are Berkeley DB 1.x, with NULL-terminated records and values stored as JSON. They're intended to be easily portable to other non-Perl applications.

AUTHOR

Jon Portnoy <avenj@cobaltirc.org>