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

Comparing BDB/BDB.pm (file contents):
Revision 1.7 by root, Mon Mar 5 19:47:01 2007 UTC vs.
Revision 1.29 by root, Sat Dec 22 07:33:48 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB;	7	use BDB;
8		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 result processing with AnyEvent:
		33	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		34	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		35
		36	# automatic result processing with EV:
		37	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		38
		39	# with Glib:
		40	add_watch Glib::IO BDB::poll_fileno,
		41	in => sub { BDB::poll_cb; 1 };
		42
		43	# or simply flush manually
		44	BDB::flush;
		45
		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	See the eg/ directory in the distribution and the berkeleydb C	49	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12	documentation. This is inadequate, but the only sources of documentation	50	The BDB API is very similar to the C API (the translation has been very faithful).
13	known for this module so far.
14		51
15	=head2 EXAMPLE	52	See also the example sections in the document below and possibly the eg/
		53	subdirectory of the BDB distribution. Last not least see the IO::AIO
		54	documentation, as that module uses almost the same asynchronous request
		55	model as this module.
		56
		57	I know this is woefully inadequate documentation. Send a patch!
		58
16		59
17	=head1 REQUEST ANATOMY AND LIFETIME	60	=head1 REQUEST ANATOMY AND LIFETIME
18		61
19	Every request method creates a request. which is a C data structure not	62	Every request method creates a request. which is a C data structure not
20	directly visible to Perl.	63	directly visible to Perl.
…		…
67	use strict 'vars';	110	use strict 'vars';
68		111
69	use base 'Exporter';	112	use base 'Exporter';
70		113
71	BEGIN {	114	BEGIN {
72	our $VERSION = '0.1';	115	our $VERSION = '1.41';
73		116
74	our @BDB_REQ = qw(	117	our @BDB_REQ = qw(
75	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect	118	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
76	db_env_memp_sync db_env_memp_trickle	119	db_env_memp_sync db_env_memp_trickle
77	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range	120	db_open db_close db_compact db_sync db_upgrade
		121	db_put db_get db_pget db_del db_key_range
78	db_txn_commit db_txn_abort	122	db_txn_commit db_txn_abort db_txn_finish
79	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del	123	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
80	db_sequence_open db_sequence_close	124	db_sequence_open db_sequence_close
81	db_sequence_get db_sequence_remove	125	db_sequence_get db_sequence_remove
82	);	126	);
83	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));	127	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
…		…
90		134
91	require XSLoader;	135	require XSLoader;
92	XSLoader::load ("BDB", $VERSION);	136	XSLoader::load ("BDB", $VERSION);
93	}	137	}
94		138
		139	=head2 BERKELEYDB FUNCTIONS
		140
		141	All of these are functions. The create functions simply return a new
		142	object and never block. All the remaining functions all take an optional
		143	callback as last argument. If it is missing, then the function will be
		144	executed synchronously. In both cases, C<$!> will reflect the return value
		145	of the function.
		146
		147	BDB functions that cannot block (mostly functions that manipulate
		148	settings) are method calls on the relevant objects, so the rule of thumb
		149	is: if its a method, its not blocking, if its a function, it takes a
		150	callback as last argument.
		151
		152	In the following, C<$int> signifies an integer return value,
		153	C<octetstring> is a "binary string" (i.e. a perl string with no character
		154	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		155	integer, C<NV> is a floating point value.
		156
		157	The C<SV *> types are generic perl scalars (for input and output of data
		158	values), and the C<SV *callback> is the optional callback function to call
		159	when the request is completed.
		160
		161	The various C<DB_ENV> etc. arguments are handles return by
		162	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		163	appended C<_ornull> this means they are optional and you can pass C<undef>
		164	for them, resulting a NULL pointer on the C level.
		165
		166	=head3 BDB functions
		167
		168	Functions in the BDB namespace, exported by default:
		169
		170	$env = db_env_create (U32 env_flags = 0)
		171	flags: RPCCLIENT
		172
		173	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		174	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
		175	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		176	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		177	flags: FORCE
		178	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		179	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		180	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		181	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		182
		183	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		184	flags: XA_CREATE
		185
		186	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		187	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		188	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		189	flags: DB_NOSYNC
		190	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		191	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)
		192	flags: FREELIST_ONLY FREE_SPACE
		193	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		194	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		195	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		196	flags: APPEND NODUPDATA NOOVERWRITE
		197	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		198	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		199	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		200	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		201	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		202	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		203	flags: TXN_NOSYNC TXN_SYNC
		204	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		205
		206	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		207	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		209	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		210	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		211	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
		212	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		213	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		214
		215	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		216	flags: CREATE EXCL
		217	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		218	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)
		219	flags: TXN_NOSYNC
		220	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		221	flags: TXN_NOSYNC
		222
		223	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		224
		225	This is not actually a Berkeley DB function but a BDB module
		226	extension. The background for this exytension is: It is very annoying to
		227	have to check every single BDB function for error returns and provide a
		228	codepath out of your transaction. While the BDB module still makes this
		229	possible, it contains the following extensions:
		230
		231	When a transaction-protected function returns any operating system
		232	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		233	transaction. This flag is also set by Berkeley DB functions themselves
		234	when an operation fails with LOCK_DEADLOCK, and it causes all further
		235	operations on that transaction (including C<db_txn_commit>) to fail.
		236
		237	The C<db_txn_finish> request will look at this flag, and, if it is set,
		238	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		239	if it isn't set to something else yet). If it isn't set, it will call
		240	C<db_txn_commit> and return the error normally.
		241
		242	How to use this? Easy: just write your transaction normally:
		243
		244	my $txn = $db_env->txn_begin;
		245	db_get $db, $txn, "key", my $data;
		246	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		247	db_txn_finish $txn;
		248	die "transaction failed" if $!;
		249
		250	That is, handle only the expected errors. If something unexpected happens
		251	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		252	requests (db_put in this case) will simply be skipped (they will fail with
		253	LOCK_DEADLOCK) and the transaction will be aborted.
		254
		255	You can use the C<< $txn->failed >> method to check wether a transaction
		256	has failed in this way and abort further processing (excluding
		257	C<db_txn_finish>).
		258
		259	=head3 DB_ENV/database environment methods
		260
		261	Methods available on DB_ENV/$env handles:
		262
		263	DESTROY (DB_ENV_ornull *env)
		264	CODE:
		265	if (env)
		266	env->close (env, 0);
		267
		268	$int = $env->set_data_dir (const char *dir)
		269	$int = $env->set_tmp_dir (const char *dir)
		270	$int = $env->set_lg_dir (const char *dir)
		271	$int = $env->set_shm_key (long shm_key)
		272	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		273	$int = $env->set_flags (U32 flags, int onoff)
		274	$env->set_errfile (FILE *errfile = 0)
		275	$env->set_msgfile (FILE *msgfile = 0)
		276	$int = $env->set_verbose (U32 which, int onoff = 1)
		277	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		278	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		279	$int = $env->set_mp_max_openfd (int maxopenfd);
		280	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		281	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		282	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		283	$int = $env->set_lk_max_lockers (U32 max)
		284	$int = $env->set_lk_max_locks (U32 max)
		285	$int = $env->set_lk_max_objects (U32 max)
		286	$int = $env->set_lg_bsize (U32 max)
		287	$int = $env->set_lg_max (U32 max)
		288	$int = $env->mutex_set_increment (U32 increment)
		289	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		290	$int = $env->mutex_set_max (U32 max)
		291	$int = $env->mutex_set_align (U32 align)
		292
		293	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		294	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		295
		296	=head4 Example:
		297
		298	use AnyEvent;
		299	use BDB;
		300
		301	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		302	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		303
		304	BDB::min_parallel 8;
		305
		306	my $env = db_env_create;
		307
		308	mkdir "bdtest", 0700;
		309	db_env_open
		310	$env,
		311	"bdtest",
		312	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		313	0600;
		314
		315	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		316
		317
		318	=head3 DB/database methods
		319
		320	Methods available on DB/$db handles:
		321
		322	DESTROY (DB_ornull *db)
		323	CODE:
		324	if (db)
		325	{
		326	SV env = (SV )db->app_private;
		327	db->close (db, 0);
		328	SvREFCNT_dec (env);
		329	}
		330
		331	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		332	$int = $db->set_flags (U32 flags)
		333	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		334	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		335	Hash: DUP DUPSORT
		336	Queue: INORDER
		337	Recno: RENUMBER SNAPSHOT
		338
		339	$int = $db->set_encrypt (const char *password, U32 flags)
		340	$int = $db->set_lorder (int lorder)
		341	$int = $db->set_bt_minkey (U32 minkey)
		342	$int = $db->set_re_delim (int delim)
		343	$int = $db->set_re_pad (int re_pad)
		344	$int = $db->set_re_source (char *source)
		345	$int = $db->set_re_len (U32 re_len)
		346	$int = $db->set_h_ffactor (U32 h_ffactor)
		347	$int = $db->set_h_nelem (U32 h_nelem)
		348	$int = $db->set_q_extentsize (U32 extentsize)
		349
		350	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		351	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		352	$seq = $db->sequence (U32 flags = 0)
		353
		354	=head4 Example:
		355
		356	my $db = db_create $env;
		357	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		358
		359	for (1..1000) {
		360	db_put $db, undef, "key $_", "data $_";
		361
		362	db_key_range $db, undef, "key $_", my $keyrange;
		363	my ($lt, $eq, $gt) = @$keyrange;
		364	}
		365
		366	db_del $db, undef, "key $_" for 1..1000;
		367
		368	db_sync $db;
		369
		370
		371	=head3 DB_TXN/transaction methods
		372
		373	Methods available on DB_TXN/$txn handles:
		374
		375	DESTROY (DB_TXN_ornull *txn)
		376	CODE:
		377	if (txn)
		378	txn->abort (txn);
		379
		380	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		381	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		382
		383	$bool = $txn->failed
		384	# see db_txn_finish documentation, above
		385
		386
		387	=head3 DBC/cursor methods
		388
		389	Methods available on DBC/$dbc handles:
		390
		391	DESTROY (DBC_ornull *dbc)
		392	CODE:
		393	if (dbc)
		394	dbc->c_close (dbc);
		395
		396	$int = $cursor->set_priority ($priority = PRIORITY_*)
		397
		398	=head4 Example:
		399
		400	my $c = $db->cursor;
		401
		402	for (;;) {
		403	db_c_get $c, my $key, my $data, BDB::NEXT;
		404	warn "<$!,$key,$data>";
		405	last if $!;
		406	}
		407
		408	db_c_close $c;
		409
		410
		411	=head3 DB_SEQUENCE/sequence methods
		412
		413	Methods available on DB_SEQUENCE/$seq handles:
		414
		415	DESTROY (DB_SEQUENCE_ornull *seq)
		416	CODE:
		417	if (seq)
		418	seq->close (seq, 0);
		419
		420	$int = $seq->initial_value (db_seq_t value)
		421	$int = $seq->set_cachesize (U32 size)
		422	$int = $seq->set_flags (U32 flags)
		423	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		424	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		425
		426	=head4 Example:
		427
		428	my $seq = $db->sequence;
		429
		430	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		431	db_sequence_get $seq, undef, 1, my $value;
		432
		433
95	=head2 SUPPORT FUNCTIONS	434	=head2 SUPPORT FUNCTIONS
96		435
97	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	436	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
98		437
99	=over 4	438	=over 4
		439
		440	=item $msg = BDB::strerror [$errno]
		441
		442	Returns the string corresponding to the given errno value. If no argument
		443	is given, use C<$!>.
100		444
101	=item $fileno = BDB::poll_fileno	445	=item $fileno = BDB::poll_fileno
102		446
103	Return the I<request result pipe file descriptor>. This filehandle must be	447	Return the I<request result pipe file descriptor>. This filehandle must be
104	polled for reading by some mechanism outside this module (e.g. Event or	448	polled for reading by some mechanism outside this module (e.g. Event or
…		…
143	interactiveness when perl is not fast enough to process all requests in	487	interactiveness when perl is not fast enough to process all requests in
144	time.	488	time.
145		489
146	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	490	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
147		491
148	Example: Install an Event watcher that automatically calls	492	Example: Install an EV watcher that automatically calls
149	BDB::poll_cb with low priority, to ensure that other parts of the	493	BDB::poll_cb with low priority, to ensure that other parts of the
150	program get the CPU sometimes even under high AIO load.	494	program get the CPU sometimes even under high load.
151		495
152	# try not to spend much more than 0.1s in poll_cb	496	# try not to spend much more than 0.1s in poll_cb
153	BDB::max_poll_time 0.1;	497	BDB::max_poll_time 0.1;
154		498
155	# use a low priority so other tasks have priority	499	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
156	Event->io (fd => BDB::poll_fileno,
157	poll => 'r', nice => 1,
158	cb => &BDB::poll_cb);
159		500
160	=item BDB::poll_wait	501	=item BDB::poll_wait
161		502
162	If there are any outstanding requests and none of them in the result	503	If there are any outstanding requests and none of them in the result
163	phase, wait till the result filehandle becomes ready for reading (simply	504	phase, wait till the result filehandle becomes ready for reading (simply
…		…
175		516
176	BDB::poll_wait, BDB::poll_cb	517	BDB::poll_wait, BDB::poll_cb
177		518
178	=item BDB::flush	519	=item BDB::flush
179		520
180	Wait till all outstanding AIO requests have been handled.	521	Wait till all outstanding BDB requests have been handled.
181		522
182	Strictly equivalent to:	523	Strictly equivalent to:
183		524
184	BDB::poll_wait, BDB::poll_cb	525	BDB::poll_wait, BDB::poll_cb
185	while BDB::nreqs;	526	while BDB::nreqs;
186		527
		528	=back
		529
187	=head3 CONTROLLING THE NUMBER OF THREADS	530	=head3 CONTROLLING THE NUMBER OF THREADS
188		531
		532	=over 4
		533
189	=item BDB::min_parallel $nthreads	534	=item BDB::min_parallel $nthreads
190		535
191	Set the minimum number of AIO threads to C<$nthreads>. The current	536	Set the minimum number of BDB threads to C<$nthreads>. The current
192	default is C<8>, which means eight asynchronous operations can execute	537	default is C<8>, which means eight asynchronous operations can execute
193	concurrently at any one time (the number of outstanding requests,	538	concurrently at any one time (the number of outstanding requests,
194	however, is unlimited).	539	however, is unlimited).
195		540
196	BDB starts threads only on demand, when an AIO request is queued and	541	BDB starts threads only on demand, when an BDB request is queued and
197	no free thread exists. Please note that queueing up a hundred requests can	542	no free thread exists. Please note that queueing up a hundred requests can
198	create demand for a hundred threads, even if it turns out that everything	543	create demand for a hundred threads, even if it turns out that everything
199	is in the cache and could have been processed faster by a single thread.	544	is in the cache and could have been processed faster by a single thread.
200		545
201	It is recommended to keep the number of threads relatively low, as some	546	It is recommended to keep the number of threads relatively low, as some
…		…
206	Under most circumstances you don't need to call this function, as the	551	Under most circumstances you don't need to call this function, as the
207	module selects a default that is suitable for low to moderate load.	552	module selects a default that is suitable for low to moderate load.
208		553
209	=item BDB::max_parallel $nthreads	554	=item BDB::max_parallel $nthreads
210		555
211	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	556	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
212	specified number of threads are currently running, this function kills	557	specified number of threads are currently running, this function kills
213	them. This function blocks until the limit is reached.	558	them. This function blocks until the limit is reached.
214		559
215	While C<$nthreads> are zero, aio requests get queued but not executed	560	While C<$nthreads> are zero, aio requests get queued but not executed
216	until the number of threads has been increased again.	561	until the number of threads has been increased again.
…		…
319		664
320	=head2 FORK BEHAVIOUR	665	=head2 FORK BEHAVIOUR
321		666
322	This module should do "the right thing" when the process using it forks:	667	This module should do "the right thing" when the process using it forks:
323		668
324	Before the fork, IO::AIO enters a quiescent state where no requests	669	Before the fork, BDB enters a quiescent state where no requests
325	can be added in other threads and no results will be processed. After	670	can be added in other threads and no results will be processed. After
326	the fork the parent simply leaves the quiescent state and continues	671	the fork the parent simply leaves the quiescent state and continues
327	request/result processing, while the child frees the request/result queue	672	request/result processing, while the child frees the request/result queue
328	(so that the requests started before the fork will only be handled in the	673	(so that the requests started before the fork will only be handled in the
329	parent). Threads will be started on demand until the limit set in the	674	parent). Threads will be started on demand until the limit set in the
330	parent process has been reached again.	675	parent process has been reached again.
331		676
332	In short: the parent will, after a short pause, continue as if fork had	677	In short: the parent will, after a short pause, continue as if fork had
333	not been called, while the child will act as if IO::AIO has not been used	678	not been called, while the child will act as if BDB has not been used
334	yet.	679	yet.
		680
		681	Win32 note: there is no fork on win32, and perls emulation of it is too
		682	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		683	yet, switch to a more capable platform.
335		684
336	=head2 MEMORY USAGE	685	=head2 MEMORY USAGE
337		686
338	Per-request usage:	687	Per-request usage:
339		688
…		…
341	bytes of memory. In addition, stat requests need a stat buffer (possibly	690	bytes of memory. In addition, stat requests need a stat buffer (possibly
342	a few hundred bytes), readdir requires a result buffer and so on. Perl	691	a few hundred bytes), readdir requires a result buffer and so on. Perl
343	scalars and other data passed into aio requests will also be locked and	692	scalars and other data passed into aio requests will also be locked and
344	will consume memory till the request has entered the done state.	693	will consume memory till the request has entered the done state.
345		694
346	This is now awfully much, so queuing lots of requests is not usually a	695	This is not awfully much, so queuing lots of requests is not usually a
347	problem.	696	problem.
348		697
349	Per-thread usage:	698	Per-thread usage:
350		699
351	In the execution phase, some aio requests require more memory for	700	In the execution phase, some aio requests require more memory for
352	temporary buffers, and each thread requires a stack and other data	701	temporary buffers, and each thread requires a stack and other data
353	structures (usually around 16k-128k, depending on the OS).	702	structures (usually around 16k-128k, depending on the OS).
354		703
355	=head1 KNOWN BUGS	704	=head1 KNOWN BUGS
356		705
357	Known bugs will be fixed in the next release.	706	Known bugs will be fixed in the next release, except:
		707
		708	If you use a transaction in any request, and the request returns
		709	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		710	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		711	above.
358		712
359	=head1 SEE ALSO	713	=head1 SEE ALSO
360		714
361	L<Coro::AIO>.	715	L<Coro::BDB>, L<IO::AIO>.
362		716
363	=head1 AUTHOR	717	=head1 AUTHOR
364		718
365	Marc Lehmann <schmorp@schmorp.de>	719	Marc Lehmann <schmorp@schmorp.de>
366	http://home.schmorp.de/	720	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing BDB/BDB.pm (file contents): Revision 1.7 by root, Mon Mar 5 19:47:01 2007 UTC vs. Revision 1.29 by root, Sat Dec 22 07:33:48 2007 UTC

Diff Legend

Comparing BDB/BDB.pm (file contents):
Revision 1.7 by root, Mon Mar 5 19:47:01 2007 UTC vs.
Revision 1.29 by root, Sat Dec 22 07:33:48 2007 UTC