[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 1.44 by root, Wed Jul 9 21:08:29 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
67	BEGIN {	113	BEGIN {
68	our $VERSION = '0.1';	114	our $VERSION = '1.7';
69		115
70	our @BDB_REQ = qw();	116	our @BDB_REQ = qw(
		117	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		118	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
		119	db_open db_close db_compact db_sync db_upgrade
		120	db_put db_exists db_get db_pget db_del db_key_range
		121	db_txn_commit db_txn_abort db_txn_finish
		122	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		123	db_sequence_open db_sequence_close
		124	db_sequence_get db_sequence_remove
		125	);
		126	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		127	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	128	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	129	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	130	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	131	max_poll_time max_poll_reqs
		132	);
75		133
76	require XSLoader;	134	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	135	XSLoader::load ("BDB", $VERSION);
78	}	136	}
79		137
		138	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		139
		140	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		141	an internal flag to store wether a filename is Unicode or ANSI, but that
		142	flag is used for somethign else in the perl core, so there is no way to
		143	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		144	tries to work around this issue by assuming that the filename is an ANSI
		145	filename and BDB was built for unicode support.
		146
		147	=head2 BERKELEYDB FUNCTIONS
		148
		149	All of these are functions. The create functions simply return a new
		150	object and never block. All the remaining functions take an optional
		151	callback as last argument. If it is missing, then the function will be
		152	executed synchronously. In both cases, C<$!> will reflect the return value
		153	of the function.
		154
		155	BDB functions that cannot block (mostly functions that manipulate
		156	settings) are method calls on the relevant objects, so the rule of thumb
		157	is: if it's a method, it's not blocking, if it's a function, it takes a
		158	callback as last argument.
		159
		160	In the following, C<$int> signifies an integer return value,
		161	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		162	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		163	floating point value.
		164
		165	Most C<SV *> types are generic perl scalars (for input and output of data
		166	values).
		167
		168	The various C<DB_ENV> etc. arguments are handles return by
		169	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		170	appended C<_ornull> this means they are optional and you can pass C<undef>
		171	for them, resulting a NULL pointer on the C level.
		172
		173	The C<SV *callback> is the optional callback function to call when the
		174	request is completed. This last callback argument is special: the callback
		175	is simply the last argument passed. If there are "optional" arguments
		176	before the callback they can be left out. The callback itself can be left
		177	out or specified as C<undef>, in which case the function will be executed
		178	synchronously.
		179
		180	For example, C<db_env_txn_checkpoint> usually is called with all integer
		181	arguments zero. These can be left out, so all of these specify a call
		182	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		183	callback to be called:
		184
		185	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		186	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		187	db_env_txn_checkpoint $db_env, sub { };
		188
		189	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		190	executed synchronously:
		191
		192	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		193	db_env_txn_checkpoint $db_env, 0, 0, 0;
		194	db_env_txn_checkpoint $db_env, 0;
		195
		196	=head3 BDB functions
		197
		198	Functions in the BDB namespace, exported by default:
		199
		200	$env = db_env_create (U32 env_flags = 0)
		201	flags: RPCCLIENT
		202
		203	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		204	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
		205	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		206	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		207	flags: FORCE
		208	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		209	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		210	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		211	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		212	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		213	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)
		214
		215	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		216	flags: XA_CREATE
		217
		218	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)
		219	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		220	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		221	flags: DB_NOSYNC
		222	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		223	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)
		224	flags: FREELIST_ONLY FREE_SPACE
		225	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		226	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		227	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		228	flags: APPEND NODUPDATA NOOVERWRITE
		229	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0)
		230	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		231	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		232	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		233	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		234	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		235	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		236	flags: TXN_NOSYNC TXN_SYNC
		237	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		238
		239	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		240	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		241	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		242	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		243	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		244	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
		245	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		246	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		247
		248	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		249	flags: CREATE EXCL
		250	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		251	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)
		252	flags: TXN_NOSYNC
		253	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		254	flags: TXN_NOSYNC
		255
		256	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		257
		258	This is not actually a Berkeley DB function but a BDB module
		259	extension. The background for this exytension is: It is very annoying to
		260	have to check every single BDB function for error returns and provide a
		261	codepath out of your transaction. While the BDB module still makes this
		262	possible, it contains the following extensions:
		263
		264	When a transaction-protected function returns any operating system
		265	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		266	transaction. This flag is also set by Berkeley DB functions themselves
		267	when an operation fails with LOCK_DEADLOCK, and it causes all further
		268	operations on that transaction (including C<db_txn_commit>) to fail.
		269
		270	The C<db_txn_finish> request will look at this flag, and, if it is set,
		271	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		272	if it isn't set to something else yet). If it isn't set, it will call
		273	C<db_txn_commit> and return the error normally.
		274
		275	How to use this? Easy: just write your transaction normally:
		276
		277	my $txn = $db_env->txn_begin;
		278	db_get $db, $txn, "key", my $data;
		279	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		280	db_txn_finish $txn;
		281	die "transaction failed" if $!;
		282
		283	That is, handle only the expected errors. If something unexpected happens
		284	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		285	requests (db_put in this case) will simply be skipped (they will fail with
		286	LOCK_DEADLOCK) and the transaction will be aborted.
		287
		288	You can use the C<< $txn->failed >> method to check wether a transaction
		289	has failed in this way and abort further processing (excluding
		290	C<db_txn_finish>).
		291
		292	=head3 DB_ENV/database environment methods
		293
		294	Methods available on DB_ENV/$env handles:
		295
		296	DESTROY (DB_ENV_ornull *env)
		297	CODE:
		298	if (env)
		299	env->close (env, 0);
		300
		301	$int = $env->set_data_dir (const char *dir)
		302	$int = $env->set_tmp_dir (const char *dir)
		303	$int = $env->set_lg_dir (const char *dir)
		304	$int = $env->set_shm_key (long shm_key)
		305	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		306	$int = $env->set_flags (U32 flags, int onoff = 1)
		307	$int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
		308	$int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
		309	$env->set_errfile (FILE *errfile = 0)
		310	$env->set_msgfile (FILE *msgfile = 0)
		311	$int = $env->set_verbose (U32 which, int onoff = 1)
		312	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		313	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		314	$int = $env->set_mp_max_openfd (int maxopenfd);
		315	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		316	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		317	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		318	$int = $env->set_lk_max_lockers (U32 max)
		319	$int = $env->set_lk_max_locks (U32 max)
		320	$int = $env->set_lk_max_objects (U32 max)
		321	$int = $env->set_lg_bsize (U32 max)
		322	$int = $env->set_lg_max (U32 max)
		323	$int = $env->mutex_set_increment (U32 increment)
		324	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		325	$int = $env->mutex_set_max (U32 max)
		326	$int = $env->mutex_set_align (U32 align)
		327
		328	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		329	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		330	$txn = $env->cdsgroup_begin;
		331
		332	=head4 Example:
		333
		334	use AnyEvent;
		335	use BDB;
		336
		337	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		338	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		339
		340	BDB::min_parallel 8;
		341
		342	my $env = db_env_create;
		343
		344	mkdir "bdtest", 0700;
		345	db_env_open
		346	$env,
		347	"bdtest",
		348	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		349	0600;
		350
		351	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		352
		353
		354	=head3 DB/database methods
		355
		356	Methods available on DB/$db handles:
		357
		358	DESTROY (DB_ornull *db)
		359	CODE:
		360	if (db)
		361	{
		362	SV env = (SV )db->app_private;
		363	db->close (db, 0);
		364	SvREFCNT_dec (env);
		365	}
		366
		367	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		368	$int = $db->set_flags (U32 flags)
		369	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		370	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		371	Hash: DUP DUPSORT
		372	Queue: INORDER
		373	Recno: RENUMBER SNAPSHOT
		374
		375	$int = $db->set_encrypt (const char *password, U32 flags)
		376	$int = $db->set_lorder (int lorder)
		377	$int = $db->set_bt_minkey (U32 minkey)
		378	$int = $db->set_re_delim (int delim)
		379	$int = $db->set_re_pad (int re_pad)
		380	$int = $db->set_re_source (char *source)
		381	$int = $db->set_re_len (U32 re_len)
		382	$int = $db->set_h_ffactor (U32 h_ffactor)
		383	$int = $db->set_h_nelem (U32 h_nelem)
		384	$int = $db->set_q_extentsize (U32 extentsize)
		385
		386	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		387	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		388	$seq = $db->sequence (U32 flags = 0)
		389
		390	=head4 Example:
		391
		392	my $db = db_create $env;
		393	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		394
		395	for (1..1000) {
		396	db_put $db, undef, "key $_", "data $_";
		397
		398	db_key_range $db, undef, "key $_", my $keyrange;
		399	my ($lt, $eq, $gt) = @$keyrange;
		400	}
		401
		402	db_del $db, undef, "key $_" for 1..1000;
		403
		404	db_sync $db;
		405
		406
		407	=head3 DB_TXN/transaction methods
		408
		409	Methods available on DB_TXN/$txn handles:
		410
		411	DESTROY (DB_TXN_ornull *txn)
		412	CODE:
		413	if (txn)
		414	txn->abort (txn);
		415
		416	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		417	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		418
		419	$bool = $txn->failed
		420	# see db_txn_finish documentation, above
		421
		422
		423	=head3 DBC/cursor methods
		424
		425	Methods available on DBC/$dbc handles:
		426
		427	DESTROY (DBC_ornull *dbc)
		428	CODE:
		429	if (dbc)
		430	dbc->c_close (dbc);
		431
		432	$int = $cursor->set_priority ($priority = PRIORITY_*)
		433
		434	=head4 Example:
		435
		436	my $c = $db->cursor;
		437
		438	for (;;) {
		439	db_c_get $c, my $key, my $data, BDB::NEXT;
		440	warn "<$!,$key,$data>";
		441	last if $!;
		442	}
		443
		444	db_c_close $c;
		445
		446
		447	=head3 DB_SEQUENCE/sequence methods
		448
		449	Methods available on DB_SEQUENCE/$seq handles:
		450
		451	DESTROY (DB_SEQUENCE_ornull *seq)
		452	CODE:
		453	if (seq)
		454	seq->close (seq, 0);
		455
		456	$int = $seq->initial_value (db_seq_t value)
		457	$int = $seq->set_cachesize (U32 size)
		458	$int = $seq->set_flags (U32 flags)
		459	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		460	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		461
		462	=head4 Example:
		463
		464	my $seq = $db->sequence;
		465
		466	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		467	db_sequence_get $seq, undef, 1, my $value;
		468
		469
80	=head2 SUPPORT FUNCTIONS	470	=head2 SUPPORT FUNCTIONS
81		471
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	472	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		473
84	=over 4	474	=over 4
85		475
		476	=item $msg = BDB::strerror [$errno]
		477
		478	Returns the string corresponding to the given errno value. If no argument
		479	is given, use C<$!>.
		480
		481	Note that the BDB module also patches the C<$!> variable directly, so you
		482	should be able to get a bdb error string by simply stringifying C<$!>.
		483
86	=item $fileno = BDB::AIO::poll_fileno	484	=item $fileno = BDB::poll_fileno
87		485
88	Return the I<request result pipe file descriptor>. This filehandle must be	486	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	487	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	488	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	489	to call C<poll_cb> to check the results.
92		490
93	See C<poll_cb> for an example.	491	See C<poll_cb> for an example.
94		492
95	=item BDB::AIO::poll_cb	493	=item BDB::poll_cb
96		494
97	Process some outstanding events on the result pipe. You have to call this	495	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	496	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	497	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>.	498	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		499
102	If not all requests were processed for whatever reason, the filehandle	500	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	501	will still be ready when C<poll_cb> returns.
104		502
105	Example: Install an Event watcher that automatically calls	503	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	504	BDB::poll_cb with high priority:
107		505
108	Event->io (fd => BDB::AIO::poll_fileno,	506	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	507	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	508	cb => \&BDB::poll_cb);
111		509
112	=item BDB::AIO::max_poll_reqs $nreqs	510	=item BDB::max_poll_reqs $nreqs
113		511
114	=item BDB::AIO::max_poll_time $seconds	512	=item BDB::max_poll_time $seconds
115		513
116	These set the maximum number of requests (default C<0>, meaning infinity)	514	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	515	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	516	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	517	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	518	of time C<poll_cb> is allowed to use).
121		519
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	520	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	521	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	522	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	526	interactiveness when perl is not fast enough to process all requests in
129	time.	527	time.
130		528
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	529	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		530
133	Example: Install an Event watcher that automatically calls	531	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	532	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	533	program get the CPU sometimes even under high load.
136		534
137	# try not to spend much more than 0.1s in poll_cb	535	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	536	BDB::max_poll_time 0.1;
139		537
140	# use a low priority so other tasks have priority	538	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		539
145	=item BDB::AIO::poll_wait	540	=item BDB::poll_wait
146		541
147	If there are any outstanding requests and none of them in the result	542	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	543	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	544	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	545	synchronously wait for some requests to finish).
151		546
152	See C<nreqs> for an example.	547	See C<nreqs> for an example.
153		548
154	=item BDB::AIO::poll	549	=item BDB::poll
155		550
156	Waits until some requests have been handled.	551	Waits until some requests have been handled.
157		552
158	Returns the number of requests processed, but is otherwise strictly	553	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	554	equivalent to:
160		555
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	556	BDB::poll_wait, BDB::poll_cb
162		557
163	=item BDB::AIO::flush	558	=item BDB::flush
164		559
165	Wait till all outstanding AIO requests have been handled.	560	Wait till all outstanding BDB requests have been handled.
166		561
167	Strictly equivalent to:	562	Strictly equivalent to:
168		563
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	564	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	565	while BDB::nreqs;
		566
		567	=back
		568
		569	=head3 VERSION CHECKING
		570
		571	BerkeleyDB comes in various versions, many of them have minor
		572	incompatibilities. This means that traditional "at least version x.x"
		573	checks are often not sufficient.
		574
		575	Example: set the log_autoremove option in a way compatible with <v.47 and
		576	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		577	bug when the symbol isn't available.
		578
		579	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		580	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		581
		582	=over 4
		583
		584	=item BDB::VERSION
		585
		586	The C<BDB::VERSION> function, when called without arguments, returns the
		587	Berkeley DB version as a v-string (usually with 3 components). You should
		588	use C<lt> and C<ge> operators exclusively to make comparisons.
		589
		590	Example: check for at least version 4.7.
		591
		592	BDB::VERSION ge v4.7 or die;
		593
		594	=item BDB::VERSION min-version
		595
		596	Returns true if the BDB version is at least the given version (specified
		597	as a v-string), false otherwise.
		598
		599	Example: check for at least version 4.5.
		600
		601	BDB::VERSION v4.7 or die;
		602
		603	=item BDB::VERSION min-version, max-version
		604
		605	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		606	and less then C<max-version>.
		607
		608	Example: check wether version is strictly less then v4.7.
		609
		610	BDB::VERSION v0, v4.7
		611	or die "version 4.7 is not yet supported";
		612
		613	=back
		614
		615	=cut
		616
		617	sub VERSION {
		618	if (@_ > 0) {
		619	return undef if VERSION_v lt $_[0];
		620	if (@_ > 1) {
		621	return undef if VERSION_v ge $_[1];
		622	}
		623	}
		624
		625	VERSION_v
		626	}
171		627
172	=head3 CONTROLLING THE NUMBER OF THREADS	628	=head3 CONTROLLING THE NUMBER OF THREADS
173		629
		630	=over 4
		631
174	=item BDB::AIO::min_parallel $nthreads	632	=item BDB::min_parallel $nthreads
175		633
176	Set the minimum number of AIO threads to C<$nthreads>. The current	634	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	635	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	636	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	637	however, is unlimited).
180		638
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	639	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	640	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	641	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.	642	is in the cache and could have been processed faster by a single thread.
185		643
186	It is recommended to keep the number of threads relatively low, as some	644	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	647	versions, 4-32 threads should be fine.
190		648
191	Under most circumstances you don't need to call this function, as the	649	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.	650	module selects a default that is suitable for low to moderate load.
193		651
194	=item BDB::AIO::max_parallel $nthreads	652	=item BDB::max_parallel $nthreads
195		653
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	654	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	655	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	656	them. This function blocks until the limit is reached.
199		657
200	While C<$nthreads> are zero, aio requests get queued but not executed	658	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	659	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	661	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.	662	that all threads are killed and that there are no outstanding requests.
205		663
206	Under normal circumstances you don't need to call this function.	664	Under normal circumstances you don't need to call this function.
207		665
208	=item BDB::AIO::max_idle $nthreads	666	=item BDB::max_idle $nthreads
209		667
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	668	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	669	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	670	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	671	idle, it will free its resources and exit.
…		…
218		676
219	The default is probably ok in most situations, especially if thread	677	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	678	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	679	want to use larger values.
222		680
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	681	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		682
225	This is a very bad function to use in interactive programs because it	683	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	684	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	685	use an C<aio_group> together with a feed callback.
228		686
…		…
236		694
237	You can still queue as many requests as you want. Therefore,	695	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	696	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).	697	as a stop gap to shield against fatal memory overflow (with large values).
240		698
		699	=item BDB::set_sync_prepare $cb
		700
		701	Sets a callback that is called whenever a request is created without an
		702	explicit callback. It has to return two code references. The first is used
		703	as the request callback (it should save the return status), and the second
		704	is called to wait until the first callback has been called (it must set
		705	C<$!> to the return status).
		706
		707	This mechanism can be used to include BDB into other event mechanisms,
		708	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		709
		710	The default implementation works like this:
		711
		712	sub {
		713	my $status;
		714	(
		715	sub { $status = $! },
		716	sub { BDB::poll while !defined $status; $! = $status },
		717	)
		718	}
		719
		720	It simply blocks the process till the request has finished and then sets
		721	C<$!> to the return value. This means that if you don't use a callback,
		722	BDB will simply fall back to synchronous operations.
		723
		724	=back
		725
241	=head3 STATISTICAL INFORMATION	726	=head3 STATISTICAL INFORMATION
242		727
		728	=over 4
		729
243	=item BDB::AIO::nreqs	730	=item BDB::nreqs
244		731
245	Returns the number of requests currently in the ready, execute or pending	732	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).	733	states (i.e. for which their callback has not been invoked yet).
247		734
248	Example: wait till there are no outstanding requests anymore:	735	Example: wait till there are no outstanding requests anymore:
249		736
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	737	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	738	while BDB::nreqs;
252		739
253	=item BDB::AIO::nready	740	=item BDB::nready
254		741
255	Returns the number of requests currently in the ready state (not yet	742	Returns the number of requests currently in the ready state (not yet
256	executed).	743	executed).
257		744
258	=item BDB::AIO::npending	745	=item BDB::npending
259		746
260	Returns the number of requests currently in the pending state (executed,	747	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	748	but not yet processed by poll_cb).
262		749
263	=back	750	=back
264		751
265	=cut	752	=cut
266		753
267	# support function to convert a fd into a perl filehandle	754	set_sync_prepare {
268	sub _fd2fh {	755	my $status;
269	return undef if $_[0] < 0;	756	(
270		757	sub {
271	# try to generate nice filehandles	758	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	759	},
273	local *$sym;	760	sub {
274		761	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	762	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	763	},
277	or open *$sym, ">&=$_[0]" # or this	764	)
278	or return undef;	765	};
279
280	*$sym
281	}
282		766
283	min_parallel 8;	767	min_parallel 8;
284		768
285	END { flush }	769	END { flush }
286		770
…		…
288		772
289	=head2 FORK BEHAVIOUR	773	=head2 FORK BEHAVIOUR
290		774
291	This module should do "the right thing" when the process using it forks:	775	This module should do "the right thing" when the process using it forks:
292		776
293	Before the fork, IO::AIO enters a quiescent state where no requests	777	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	778	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	779	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	780	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	781	(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	782	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	783	parent process has been reached again.
300		784
301	In short: the parent will, after a short pause, continue as if fork had	785	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	786	not been called, while the child will act as if BDB has not been used
303	yet.	787	yet.
		788
		789	Win32 note: there is no fork on win32, and perls emulation of it is too
		790	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		791	yet, switch to a more capable platform.
304		792
305	=head2 MEMORY USAGE	793	=head2 MEMORY USAGE
306		794
307	Per-request usage:	795	Per-request usage:
308		796
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	798	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	799	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	800	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.	801	will consume memory till the request has entered the done state.
314		802
315	This is now awfully much, so queuing lots of requests is not usually a	803	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	804	problem.
317		805
318	Per-thread usage:	806	Per-thread usage:
319		807
320	In the execution phase, some aio requests require more memory for	808	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	809	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	810	structures (usually around 16k-128k, depending on the OS).
323		811
324	=head1 KNOWN BUGS	812	=head1 KNOWN BUGS
325		813
326	Known bugs will be fixed in the next release.	814	Known bugs will be fixed in the next release, except:
		815
		816	If you use a transaction in any request, and the request returns
		817	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		818	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		819	above.
327		820
328	=head1 SEE ALSO	821	=head1 SEE ALSO
329		822
330	L<Coro::AIO>.	823	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		824	syntax), L<IO::AIO> (nice to have).
331		825
332	=head1 AUTHOR	826	=head1 AUTHOR
333		827
334	Marc Lehmann <schmorp@schmorp.de>	828	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	829	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 1.44 by root, Wed Jul 9 21:08:29 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 1.44 by root, Wed Jul 9 21:08:29 2008 UTC