[ViewVC] Diff of: cvs/BDB/BDB.pm

Comparing BDB/BDB.pm (file contents):
Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	BDB::AIO - Asynchronous Berkeley DB access	3	BDB - Asynchronous Berkeley DB access
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB::AIO;	7	use BDB;
		8
		9	my $env = db_env_create;
		10
		11	mkdir "bdtest", 0700;
		12	db_env_open
		13	$env,
		14	"bdtest",
		15	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL
		16	\| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		17	0600;
		18
		19	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		20
		21	my $db = db_create $env;
		22	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE
		23	\| BDB::READ_UNCOMMITTED, 0600;
		24	db_put $db, undef, "key", "data", 0, sub {
		25	db_del $db, undef, "key";
		26	};
		27	db_sync $db;
		28
		29	# when you also use Coro, management is easy:
		30	use Coro::BDB;
		31
		32	# automatic event loop intergration with AnyEvent:
		33	use AnyEvent::BDB;
		34
		35	# automatic result processing with EV:
		36	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		37
		38	# with Glib:
		39	add_watch Glib::IO BDB::poll_fileno,
		40	in => sub { BDB::poll_cb; 1 };
		41
		42	# or simply flush manually
		43	BDB::flush;
		44
8		45
9	=head1 DESCRIPTION	46	=head1 DESCRIPTION
10		47
11	=head2 EXAMPLE	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		49	The BDB API is very similar to the C API (the translation has been very faithful).
		50
		51	See also the example sections in the document below and possibly the eg/
		52	subdirectory of the BDB distribution. Last not least see the IO::AIO
		53	documentation, as that module uses almost the same asynchronous request
		54	model as this module.
		55
		56	I know this is woefully inadequate documentation. Send a patch!
		57
12		58
13	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
14		60
15	Every request method creates a request. which is a C data structure not	61	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	62	directly visible to Perl.
55		101
56	=back	102	=back
57		103
58	=cut	104	=cut
59		105
60	package BDB::AIO;	106	package BDB;
61		107
62	no warnings;	108	no warnings;
63	use strict 'vars';	109	use strict 'vars';
64		110
65	use base 'Exporter';	111	use base 'Exporter';
66		112
		113	our $VERSION;
		114
67	BEGIN {	115	BEGIN {
68	our $VERSION = '0.1';	116	$VERSION = '1.81';
69		117
70	our @BDB_REQ = qw();	118	our @BDB_REQ = qw(
		119	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		120	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
		121	db_env_log_archive
		122	db_open db_close db_compact db_sync db_upgrade
		123	db_put db_exists db_get db_pget db_del db_key_range
		124	db_txn_commit db_txn_abort db_txn_finish
		125	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		126	db_sequence_open db_sequence_close
		127	db_sequence_get db_sequence_remove
		128	);
		129	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		130	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	131	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	132	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	133	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	134	max_poll_time max_poll_reqs
		135	);
75		136
76	require XSLoader;	137	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	138	XSLoader::load ("BDB", $VERSION);
78	}	139	}
79		140
		141	=head1 BERKELEYDB FUNCTIONS
		142
		143	All of these are functions. The create functions simply return a new
		144	object and never block. All the remaining functions take an optional
		145	callback as last argument. If it is missing, then the function will be
		146	executed synchronously. In both cases, C<$!> will reflect the return value
		147	of the function.
		148
		149	BDB functions that cannot block (mostly functions that manipulate
		150	settings) are method calls on the relevant objects, so the rule of thumb
		151	is: if it's a method, it's not blocking, if it's a function, it takes a
		152	callback as last argument.
		153
		154	In the following, C<$int> signifies an integer return value,
		155	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		156	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		157	floating point value.
		158
		159	Most C<SV *> types are generic perl scalars (for input and output of data
		160	values).
		161
		162	The various C<DB_ENV> etc. arguments are handles return by
		163	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		164	appended C<_ornull> this means they are optional and you can pass C<undef>
		165	for them, resulting a NULL pointer on the C level.
		166
		167	The C<SV *callback> is the optional callback function to call when the
		168	request is completed. This last callback argument is special: the callback
		169	is simply the last argument passed. If there are "optional" arguments
		170	before the callback they can be left out. The callback itself can be left
		171	out or specified as C<undef>, in which case the function will be executed
		172	synchronously.
		173
		174	For example, C<db_env_txn_checkpoint> usually is called with all integer
		175	arguments zero. These can be left out, so all of these specify a call
		176	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		177	callback to be called:
		178
		179	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		180	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		181	db_env_txn_checkpoint $db_env, sub { };
		182
		183	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		184	executed synchronously:
		185
		186	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		187	db_env_txn_checkpoint $db_env, 0, 0, 0;
		188	db_env_txn_checkpoint $db_env, 0;
		189
		190	=head2 BDB functions
		191
		192	Functions in the BDB namespace, exported by default:
		193
		194	$env = db_env_create (U32 env_flags = 0)
		195	flags: RPCCLIENT
		196
		197	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		198	open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM
		199	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		200	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		201	flags: FORCE
		202	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		203	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		204	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		205	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		206	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		207	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	db_env_log_archive (DB_ENV env, SV listp, U32 flags = 0, SV *callback = &PL_sv_undef)
		209
		210	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		211	flags: XA_CREATE
		212
		213	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		214	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		215	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		216	flags: DB_NOSYNC
		217	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		218	db_compact (DB db, DB_TXN_ornull txn = 0, SV start = 0, SV stop = 0, SV unused1 = 0, U32 flags = DB_FREE_SPACE, SV unused2 = 0, SV *callback = &PL_sv_undef)
		219	flags: FREELIST_ONLY FREE_SPACE
		220	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		221	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		222	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		223	flags: APPEND NODUPDATA NOOVERWRITE
		224	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0) (v4.6)
		225	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		226	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		227	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		228	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		229	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		230	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		231	flags: TXN_NOSYNC TXN_SYNC
		232	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		233
		234	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		235	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		236	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		237	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		238	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		239	flags: CURRENT FIRST GET_BOTH GET_BOTH_RANGE GET_RECNO JOIN_ITEM LAST NEXT NEXT_DUP NEXT_NODUP PREV PREV_DUP PREV_NODUP SET SET_RANGE SET_RECNO READ_UNCOMMITTED MULTIPLE MULTIPLE_KEY RMW
		240	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		241	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		242
		243	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		244	flags: CREATE EXCL
		245	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		246	db_sequence_get (DB_SEQUENCE seq, DB_TXN_ornull txnid, int delta, SV seq_value, U32 flags = DB_TXN_NOSYNC, SV callback = &PL_sv_undef)
		247	flags: TXN_NOSYNC
		248	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		249	flags: TXN_NOSYNC
		250
		251	=head3 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		252
		253	This is not actually a Berkeley DB function but a BDB module
		254	extension. The background for this exytension is: It is very annoying to
		255	have to check every single BDB function for error returns and provide a
		256	codepath out of your transaction. While the BDB module still makes this
		257	possible, it contains the following extensions:
		258
		259	When a transaction-protected function returns any operating system
		260	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		261	transaction. This flag is also set by Berkeley DB functions themselves
		262	when an operation fails with LOCK_DEADLOCK, and it causes all further
		263	operations on that transaction (including C<db_txn_commit>) to fail.
		264
		265	The C<db_txn_finish> request will look at this flag, and, if it is set,
		266	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		267	if it isn't set to something else yet). If it isn't set, it will call
		268	C<db_txn_commit> and return the error normally.
		269
		270	How to use this? Easy: just write your transaction normally:
		271
		272	my $txn = $db_env->txn_begin;
		273	db_get $db, $txn, "key", my $data;
		274	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		275	db_txn_finish $txn;
		276	die "transaction failed" if $!;
		277
		278	That is, handle only the expected errors. If something unexpected happens
		279	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		280	requests (db_put in this case) will simply be skipped (they will fail with
		281	LOCK_DEADLOCK) and the transaction will be aborted.
		282
		283	You can use the C<< $txn->failed >> method to check wether a transaction
		284	has failed in this way and abort further processing (excluding
		285	C<db_txn_finish>).
		286
		287	=head2 DB_ENV/database environment methods
		288
		289	Methods available on DB_ENV/$env handles:
		290
		291	DESTROY (DB_ENV_ornull *env)
		292	CODE:
		293	if (env)
		294	env->close (env, 0);
		295
		296	$int = $env->set_data_dir (const char *dir)
		297	$int = $env->set_tmp_dir (const char *dir)
		298	$int = $env->set_lg_dir (const char *dir)
		299	$int = $env->set_shm_key (long shm_key)
		300	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		301	$int = $env->set_flags (U32 flags, int onoff = 1)
		302	$int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
		303	$int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
		304	$env->set_errfile (FILE *errfile = 0)
		305	$env->set_msgfile (FILE *msgfile = 0)
		306	$int = $env->set_verbose (U32 which, int onoff = 1)
		307	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		308	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		309	$int = $env->set_mp_max_openfd (int maxopenfd);
		310	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		311	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		312	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		313	$int = $env->set_lk_max_lockers (U32 max)
		314	$int = $env->set_lk_max_locks (U32 max)
		315	$int = $env->set_lk_max_objects (U32 max)
		316	$int = $env->set_lg_bsize (U32 max)
		317	$int = $env->set_lg_max (U32 max)
		318	$int = $env->mutex_set_increment (U32 increment)
		319	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		320	$int = $env->mutex_set_max (U32 max)
		321	$int = $env->mutex_set_align (U32 align)
		322
		323	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		324	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		325	$txn = $env->cdsgroup_begin; (v4.5)
		326
		327	=head3 Example:
		328
		329	use AnyEvent;
		330	use BDB;
		331
		332	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		333	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		334
		335	BDB::min_parallel 8;
		336
		337	my $env = db_env_create;
		338
		339	mkdir "bdtest", 0700;
		340	db_env_open
		341	$env,
		342	"bdtest",
		343	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		344	0600;
		345
		346	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		347
		348
		349	=head2 DB/database methods
		350
		351	Methods available on DB/$db handles:
		352
		353	DESTROY (DB_ornull *db)
		354	CODE:
		355	if (db)
		356	{
		357	SV env = (SV )db->app_private;
		358	db->close (db, 0);
		359	SvREFCNT_dec (env);
		360	}
		361
		362	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		363	$int = $db->set_flags (U32 flags)
		364	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		365	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		366	Hash: DUP DUPSORT
		367	Queue: INORDER
		368	Recno: RENUMBER SNAPSHOT
		369
		370	$int = $db->set_encrypt (const char *password, U32 flags)
		371	$int = $db->set_lorder (int lorder)
		372	$int = $db->set_bt_minkey (U32 minkey)
		373	$int = $db->set_re_delim (int delim)
		374	$int = $db->set_re_pad (int re_pad)
		375	$int = $db->set_re_source (char *source)
		376	$int = $db->set_re_len (U32 re_len)
		377	$int = $db->set_h_ffactor (U32 h_ffactor)
		378	$int = $db->set_h_nelem (U32 h_nelem)
		379	$int = $db->set_q_extentsize (U32 extentsize)
		380
		381	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		382	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		383	$seq = $db->sequence (U32 flags = 0)
		384
		385	=head3 Example:
		386
		387	my $db = db_create $env;
		388	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		389
		390	for (1..1000) {
		391	db_put $db, undef, "key $_", "data $_";
		392
		393	db_key_range $db, undef, "key $_", my $keyrange;
		394	my ($lt, $eq, $gt) = @$keyrange;
		395	}
		396
		397	db_del $db, undef, "key $_" for 1..1000;
		398
		399	db_sync $db;
		400
		401
		402	=head2 DB_TXN/transaction methods
		403
		404	Methods available on DB_TXN/$txn handles:
		405
		406	DESTROY (DB_TXN_ornull *txn)
		407	CODE:
		408	if (txn)
		409	txn->abort (txn);
		410
		411	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		412	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		413
		414	$bool = $txn->failed
		415	# see db_txn_finish documentation, above
		416
		417
		418	=head2 DBC/cursor methods
		419
		420	Methods available on DBC/$dbc handles:
		421
		422	DESTROY (DBC_ornull *dbc)
		423	CODE:
		424	if (dbc)
		425	dbc->c_close (dbc);
		426
		427	$int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
		428
		429	=head3 Example:
		430
		431	my $c = $db->cursor;
		432
		433	for (;;) {
		434	db_c_get $c, my $key, my $data, BDB::NEXT;
		435	warn "<$!,$key,$data>";
		436	last if $!;
		437	}
		438
		439	db_c_close $c;
		440
		441
		442	=head2 DB_SEQUENCE/sequence methods
		443
		444	Methods available on DB_SEQUENCE/$seq handles:
		445
		446	DESTROY (DB_SEQUENCE_ornull *seq)
		447	CODE:
		448	if (seq)
		449	seq->close (seq, 0);
		450
		451	$int = $seq->initial_value (db_seq_t value)
		452	$int = $seq->set_cachesize (U32 size)
		453	$int = $seq->set_flags (U32 flags)
		454	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		455	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		456
		457	=head3 Example:
		458
		459	my $seq = $db->sequence;
		460
		461	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		462	db_sequence_get $seq, undef, 1, my $value;
		463
		464
80	=head2 SUPPORT FUNCTIONS	465	=head1 SUPPORT FUNCTIONS
81		466
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	467	=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		468
84	=over 4	469	=over 4
85		470
		471	=item $msg = BDB::strerror [$errno]
		472
		473	Returns the string corresponding to the given errno value. If no argument
		474	is given, use C<$!>.
		475
		476	Note that the BDB module also patches the C<$!> variable directly, so you
		477	should be able to get a bdb error string by simply stringifying C<$!>.
		478
86	=item $fileno = BDB::AIO::poll_fileno	479	=item $fileno = BDB::poll_fileno
87		480
88	Return the I<request result pipe file descriptor>. This filehandle must be	481	Return the I<request result pipe file descriptor>. This filehandle must be
89	polled for reading by some mechanism outside this module (e.g. Event or	482	polled for reading by some mechanism outside this module (e.g. Event or
90	select, see below or the SYNOPSIS). If the pipe becomes readable you have	483	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	484	to call C<poll_cb> to check the results.
92		485
93	See C<poll_cb> for an example.	486	See C<poll_cb> for an example.
94		487
95	=item BDB::AIO::poll_cb	488	=item BDB::poll_cb
96		489
97	Process some outstanding events on the result pipe. You have to call this	490	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	491	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	492	when no events are outstanding. The amount of events processed depends on
100	the settings of C<BDB::AIO::max_poll_req> and C<BDB::AIO::max_poll_time>.	493	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		494
102	If not all requests were processed for whatever reason, the filehandle	495	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	496	will still be ready when C<poll_cb> returns.
104		497
105	Example: Install an Event watcher that automatically calls	498	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	499	BDB::poll_cb with high priority:
107		500
108	Event->io (fd => BDB::AIO::poll_fileno,	501	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	502	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	503	cb => \&BDB::poll_cb);
111		504
112	=item BDB::AIO::max_poll_reqs $nreqs	505	=item BDB::max_poll_reqs $nreqs
113		506
114	=item BDB::AIO::max_poll_time $seconds	507	=item BDB::max_poll_time $seconds
115		508
116	These set the maximum number of requests (default C<0>, meaning infinity)	509	These set the maximum number of requests (default C<0>, meaning infinity)
117	that are being processed by C<BDB::AIO::poll_cb> in one call, respectively	510	that are being processed by C<BDB::poll_cb> in one call, respectively
118	the maximum amount of time (default C<0>, meaning infinity) spent in	511	the maximum amount of time (default C<0>, meaning infinity) spent in
119	C<BDB::AIO::poll_cb> to process requests (more correctly the mininum amount	512	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	513	of time C<poll_cb> is allowed to use).
121		514
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	515	Setting C<max_poll_time> to a non-zero value creates an overhead of one
123	syscall per request processed, which is not normally a problem unless your	516	syscall per request processed, which is not normally a problem unless your
124	callbacks are really really fast or your OS is really really slow (I am	517	callbacks are really really fast or your OS is really really slow (I am
…		…
128	interactiveness when perl is not fast enough to process all requests in	521	interactiveness when perl is not fast enough to process all requests in
129	time.	522	time.
130		523
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	524	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		525
133	Example: Install an Event watcher that automatically calls	526	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	527	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	528	program get the CPU sometimes even under high load.
136		529
137	# try not to spend much more than 0.1s in poll_cb	530	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	531	BDB::max_poll_time 0.1;
139		532
140	# use a low priority so other tasks have priority	533	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
141	Event->io (fd => BDB::AIO::poll_fileno,
142	poll => 'r', nice => 1,
143	cb => &BDB::AIO::poll_cb);
144		534
145	=item BDB::AIO::poll_wait	535	=item BDB::poll_wait
146		536
147	If there are any outstanding requests and none of them in the result	537	If there are any outstanding requests and none of them in the result
148	phase, wait till the result filehandle becomes ready for reading (simply	538	phase, wait till the result filehandle becomes ready for reading (simply
149	does a C<select> on the filehandle. This is useful if you want to	539	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	540	synchronously wait for some requests to finish).
151		541
152	See C<nreqs> for an example.	542	See C<nreqs> for an example.
153		543
154	=item BDB::AIO::poll	544	=item BDB::poll
155		545
156	Waits until some requests have been handled.	546	Waits until some requests have been handled.
157		547
158	Returns the number of requests processed, but is otherwise strictly	548	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	549	equivalent to:
160		550
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	551	BDB::poll_wait, BDB::poll_cb
162		552
163	=item BDB::AIO::flush	553	=item BDB::flush
164		554
165	Wait till all outstanding AIO requests have been handled.	555	Wait till all outstanding BDB requests have been handled.
166		556
167	Strictly equivalent to:	557	Strictly equivalent to:
168		558
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	559	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	560	while BDB::nreqs;
171		561
		562	=back
		563
		564	=head2 VERSION CHECKING
		565
		566	BerkeleyDB comes in various versions, many of them have minor
		567	incompatibilities. This means that traditional "at least version x.x"
		568	checks are often not sufficient.
		569
		570	Example: set the log_autoremove option in a way compatible with <v4.7 and
		571	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		572	bug when the symbol isn't available.
		573
		574	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		575	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		576
		577	=over 4
		578
		579	=item BDB::VERSION
		580
		581	The C<BDB::VERSION> function, when called without arguments, returns the
		582	Berkeley DB version as a v-string (usually with 3 components). You should
		583	use C<lt> and C<ge> operators exclusively to make comparisons.
		584
		585	Example: check for at least version 4.7.
		586
		587	BDB::VERSION ge v4.7 or die;
		588
		589	=item BDB::VERSION min-version
		590
		591	Returns true if the BDB version is at least the given version (specified
		592	as a v-string), false otherwise.
		593
		594	Example: check for at least version 4.5.
		595
		596	BDB::VERSION v4.7 or die;
		597
		598	=item BDB::VERSION min-version, max-version
		599
		600	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		601	and less then C<max-version>.
		602
		603	Example: check wether version is strictly less then v4.7.
		604
		605	BDB::VERSION v0, v4.7
		606	or die "version 4.7 is not yet supported";
		607
		608	=back
		609
		610	=cut
		611
		612	sub VERSION {
		613	# I was dumb enough to override the VERSION method here, so let's try
		614	# to fix it up.
		615
		616	if ($_[0] eq __PACKAGE__) {
		617	$VERSION
		618	} else {
		619	if (@_ > 0) {
		620	return undef if VERSION_v lt $_[0];
		621	if (@_ > 1) {
		622	return undef if VERSION_v ge $_[1];
		623	}
		624	}
		625
		626	VERSION_v
		627	}
		628	}
		629
172	=head3 CONTROLLING THE NUMBER OF THREADS	630	=head2 CONTROLLING THE NUMBER OF THREADS
173		631
		632	=over 4
		633
174	=item BDB::AIO::min_parallel $nthreads	634	=item BDB::min_parallel $nthreads
175		635
176	Set the minimum number of AIO threads to C<$nthreads>. The current	636	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	637	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	638	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	639	however, is unlimited).
180		640
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	641	BDB starts threads only on demand, when an BDB request is queued and
182	no free thread exists. Please note that queueing up a hundred requests can	642	no free thread exists. Please note that queueing up a hundred requests can
183	create demand for a hundred threads, even if it turns out that everything	643	create demand for a hundred threads, even if it turns out that everything
184	is in the cache and could have been processed faster by a single thread.	644	is in the cache and could have been processed faster by a single thread.
185		645
186	It is recommended to keep the number of threads relatively low, as some	646	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	649	versions, 4-32 threads should be fine.
190		650
191	Under most circumstances you don't need to call this function, as the	651	Under most circumstances you don't need to call this function, as the
192	module selects a default that is suitable for low to moderate load.	652	module selects a default that is suitable for low to moderate load.
193		653
194	=item BDB::AIO::max_parallel $nthreads	654	=item BDB::max_parallel $nthreads
195		655
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	656	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	657	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	658	them. This function blocks until the limit is reached.
199		659
200	While C<$nthreads> are zero, aio requests get queued but not executed	660	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	661	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	663	This module automatically runs C<max_parallel 0> at program end, to ensure
204	that all threads are killed and that there are no outstanding requests.	664	that all threads are killed and that there are no outstanding requests.
205		665
206	Under normal circumstances you don't need to call this function.	666	Under normal circumstances you don't need to call this function.
207		667
208	=item BDB::AIO::max_idle $nthreads	668	=item BDB::max_idle $nthreads
209		669
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	670	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	671	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	672	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	673	idle, it will free its resources and exit.
…		…
218		678
219	The default is probably ok in most situations, especially if thread	679	The default is probably ok in most situations, especially if thread
220	creation is fast. If thread creation is very slow on your system you might	680	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	681	want to use larger values.
222		682
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	683	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		684
225	This is a very bad function to use in interactive programs because it	685	This is a very bad function to use in interactive programs because it
226	blocks, and a bad way to reduce concurrency because it is inexact: Better	686	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	687	use an C<aio_group> together with a feed callback.
228		688
…		…
236		696
237	You can still queue as many requests as you want. Therefore,	697	You can still queue as many requests as you want. Therefore,
238	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	698	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
239	as a stop gap to shield against fatal memory overflow (with large values).	699	as a stop gap to shield against fatal memory overflow (with large values).
240		700
		701	=item $old_cb = BDB::set_sync_prepare $cb
		702
		703	Sets a callback that is called whenever a request is created without an
		704	explicit callback. It has to return two code references. The first is used
		705	as the request callback (it should save the return status), and the second
		706	is called to wait until the first callback has been called (it must set
		707	C<$!> to the return status).
		708
		709	This mechanism can be used to include BDB into other event mechanisms,
		710	such as L<Coro::BDB>.
		711
		712	To allow other, callback-based, events to be executed while callback-less
		713	ones are run, you could use this sync prepare function:
		714
		715	sub {
		716	my $status;
		717	(
		718	sub { $status = $! },
		719	sub { BDB::poll while !defined $status; $! = $status },
		720	)
		721	}
		722
		723	It works by polling for results till the request has finished and then
		724	sets C<$!> to the return value. This means that if you don't use a
		725	callback, BDB would simply fall back to synchronous operations.
		726
		727	By default, or if the sync prepare function is set to C<undef>, is to
		728	execute callback-less BDB requests in the foreground thread, setting C<$!>
		729	to the return value, without polling for other events.
		730
		731	=back
		732
241	=head3 STATISTICAL INFORMATION	733	=head2 STATISTICAL INFORMATION
242		734
		735	=over 4
		736
243	=item BDB::AIO::nreqs	737	=item BDB::nreqs
244		738
245	Returns the number of requests currently in the ready, execute or pending	739	Returns the number of requests currently in the ready, execute or pending
246	states (i.e. for which their callback has not been invoked yet).	740	states (i.e. for which their callback has not been invoked yet).
247		741
248	Example: wait till there are no outstanding requests anymore:	742	Example: wait till there are no outstanding requests anymore:
249		743
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	744	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	745	while BDB::nreqs;
252		746
253	=item BDB::AIO::nready	747	=item BDB::nready
254		748
255	Returns the number of requests currently in the ready state (not yet	749	Returns the number of requests currently in the ready state (not yet
256	executed).	750	executed).
257		751
258	=item BDB::AIO::npending	752	=item BDB::npending
259		753
260	Returns the number of requests currently in the pending state (executed,	754	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	755	but not yet processed by poll_cb).
262		756
263	=back	757	=back
264		758
265	=cut	759	=cut
266		760
267	# support function to convert a fd into a perl filehandle	761	set_sync_prepare (undef);
268	sub _fd2fh {
269	return undef if $_[0] < 0;
270
271	# try to generate nice filehandles
272	my $sym = "BDB::AIO::fd#$_[0]";
273	local *$sym;
274
275	open *$sym, "+<&=$_[0]" # usually works under any unix
276	or open *$sym, "<&=$_[0]" # cygwin needs this
277	or open *$sym, ">&=$_[0]" # or this
278	or return undef;
279
280	*$sym
281	}
282		762
283	min_parallel 8;	763	min_parallel 8;
284		764
285	END { flush }	765	END { flush }
286		766
287	1;	767	1;
288		768
		769	=head1 COMMON PITFALLS
		770
		771	=head2 Unexpected Crashes
		772
		773	Remember that, by default, BDB will execute requests in parallel, in
		774	somewhat random order. That means that it is easy to run a C<db_get>
		775	request on thesa me database as a concurrent C<db_close> request, leading
		776	to a crash, silent data corruption, eventually the next world war on
		777	terrorism.
		778
		779	If you only ever use foreground requests (without a callback), this will
		780	not be an issue.
		781
		782	=head2 Unexpected Freezes or Deadlocks
		783
		784	Remember that, by default, BDB will execute requests in parallel, which
		785	easily leads to deadlocks (even concurrent put's on the same database can
		786	deadlock).
		787
		788	You either need to run deadlock detection (and handle the resulting
		789	errors), or make sure only one process ever updates the database, ine one
		790	thread, e.g. by using only foreground requests (without a callback).
		791
289	=head2 FORK BEHAVIOUR	792	=head1 FORK BEHAVIOUR
290		793
291	This module should do "the right thing" when the process using it forks:	794	This module should do "the right thing" when the process using it forks:
292		795
293	Before the fork, IO::AIO enters a quiescent state where no requests	796	Before the fork, BDB enters a quiescent state where no requests
294	can be added in other threads and no results will be processed. After	797	can be added in other threads and no results will be processed. After
295	the fork the parent simply leaves the quiescent state and continues	798	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	799	request/result processing, while the child frees the request/result queue
297	(so that the requests started before the fork will only be handled in the	800	(so that the requests started before the fork will only be handled in the
298	parent). Threads will be started on demand until the limit set in the	801	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	802	parent process has been reached again.
300		803
301	In short: the parent will, after a short pause, continue as if fork had	804	In short: the parent will, after a short pause, continue as if fork had
302	not been called, while the child will act as if IO::AIO has not been used	805	not been called, while the child will act as if BDB has not been used
303	yet.	806	yet.
304		807
		808	Win32 note: there is no fork on win32, and perls emulation of it is too
		809	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		810	yet, switch to a more capable platform.
		811
305	=head2 MEMORY USAGE	812	=head1 MEMORY USAGE
306		813
307	Per-request usage:	814	Per-request usage:
308		815
309	Each aio request uses - depending on your architecture - around 100-200	816	Each aio request uses - depending on your architecture - around 100-200
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	817	bytes of memory. In addition, stat requests need a stat buffer (possibly
311	a few hundred bytes), readdir requires a result buffer and so on. Perl	818	a few hundred bytes), readdir requires a result buffer and so on. Perl
312	scalars and other data passed into aio requests will also be locked and	819	scalars and other data passed into aio requests will also be locked and
313	will consume memory till the request has entered the done state.	820	will consume memory till the request has entered the done state.
314		821
315	This is now awfully much, so queuing lots of requests is not usually a	822	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	823	problem.
317		824
318	Per-thread usage:	825	Per-thread usage:
319		826
320	In the execution phase, some aio requests require more memory for	827	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	828	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	829	structures (usually around 16k-128k, depending on the OS).
323		830
		831	=head1 WIN32 FILENAMES/DATABASE NAME MESS
		832
		833	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		834	an internal flag to store wether a filename is Unicode or ANSI, but that
		835	flag is used for somethign else in the perl core, so there is no way to
		836	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		837	tries to work around this issue by assuming that the filename is an ANSI
		838	filename and BDB was built for unicode support.
		839
324	=head1 KNOWN BUGS	840	=head1 KNOWN BUGS
325		841
326	Known bugs will be fixed in the next release.	842	Known bugs will be fixed in the next release, except:
		843
		844	If you use a transaction in any request, and the request returns
		845	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		846	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		847	above.
327		848
328	=head1 SEE ALSO	849	=head1 SEE ALSO
329		850
330	L<Coro::AIO>.	851	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		852	syntax), L<IO::AIO> (nice to have).
331		853
332	=head1 AUTHOR	854	=head1 AUTHOR
333		855
334	Marc Lehmann <schmorp@schmorp.de>	856	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	857	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs. Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC