[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 1.36 by root, Sat May 10 20:23:06 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 = '1.5';
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
		119	db_open db_close db_compact db_sync db_upgrade
		120	db_put 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<octetstring> is a "binary string" (i.e. a perl string with no character
		162	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		163	integer, C<NV> is a floating point value.
		164
		165	The C<SV *> types are generic perl scalars (for input and output of data
		166	values), and the C<SV *callback> is the optional callback function to call
		167	when the request is completed.
		168
		169	The various C<DB_ENV> etc. arguments are handles return by
		170	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		171	appended C<_ornull> this means they are optional and you can pass C<undef>
		172	for them, resulting a NULL pointer on the C level.
		173
		174	=head3 BDB functions
		175
		176	Functions in the BDB namespace, exported by default:
		177
		178	$env = db_env_create (U32 env_flags = 0)
		179	flags: RPCCLIENT
		180
		181	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		182	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
		183	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		184	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		185	flags: FORCE
		186	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		187	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		188	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		189	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		190
		191	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		192	flags: XA_CREATE
		193
		194	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		195	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		196	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		197	flags: DB_NOSYNC
		198	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		199	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)
		200	flags: FREELIST_ONLY FREE_SPACE
		201	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		202	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		203	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		204	flags: APPEND NODUPDATA NOOVERWRITE
		205	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		206	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		207	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		208	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		209	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		210	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		211	flags: TXN_NOSYNC TXN_SYNC
		212	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		213
		214	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		215	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		216	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		217	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		218	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		219	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
		220	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		221	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		222
		223	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		224	flags: CREATE EXCL
		225	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		226	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)
		227	flags: TXN_NOSYNC
		228	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		229	flags: TXN_NOSYNC
		230
		231	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		232
		233	This is not actually a Berkeley DB function but a BDB module
		234	extension. The background for this exytension is: It is very annoying to
		235	have to check every single BDB function for error returns and provide a
		236	codepath out of your transaction. While the BDB module still makes this
		237	possible, it contains the following extensions:
		238
		239	When a transaction-protected function returns any operating system
		240	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		241	transaction. This flag is also set by Berkeley DB functions themselves
		242	when an operation fails with LOCK_DEADLOCK, and it causes all further
		243	operations on that transaction (including C<db_txn_commit>) to fail.
		244
		245	The C<db_txn_finish> request will look at this flag, and, if it is set,
		246	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		247	if it isn't set to something else yet). If it isn't set, it will call
		248	C<db_txn_commit> and return the error normally.
		249
		250	How to use this? Easy: just write your transaction normally:
		251
		252	my $txn = $db_env->txn_begin;
		253	db_get $db, $txn, "key", my $data;
		254	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		255	db_txn_finish $txn;
		256	die "transaction failed" if $!;
		257
		258	That is, handle only the expected errors. If something unexpected happens
		259	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		260	requests (db_put in this case) will simply be skipped (they will fail with
		261	LOCK_DEADLOCK) and the transaction will be aborted.
		262
		263	You can use the C<< $txn->failed >> method to check wether a transaction
		264	has failed in this way and abort further processing (excluding
		265	C<db_txn_finish>).
		266
		267	=head3 DB_ENV/database environment methods
		268
		269	Methods available on DB_ENV/$env handles:
		270
		271	DESTROY (DB_ENV_ornull *env)
		272	CODE:
		273	if (env)
		274	env->close (env, 0);
		275
		276	$int = $env->set_data_dir (const char *dir)
		277	$int = $env->set_tmp_dir (const char *dir)
		278	$int = $env->set_lg_dir (const char *dir)
		279	$int = $env->set_shm_key (long shm_key)
		280	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		281	$int = $env->set_flags (U32 flags, int onoff)
		282	$env->set_errfile (FILE *errfile = 0)
		283	$env->set_msgfile (FILE *msgfile = 0)
		284	$int = $env->set_verbose (U32 which, int onoff = 1)
		285	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		286	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		287	$int = $env->set_mp_max_openfd (int maxopenfd);
		288	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		289	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		290	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		291	$int = $env->set_lk_max_lockers (U32 max)
		292	$int = $env->set_lk_max_locks (U32 max)
		293	$int = $env->set_lk_max_objects (U32 max)
		294	$int = $env->set_lg_bsize (U32 max)
		295	$int = $env->set_lg_max (U32 max)
		296	$int = $env->mutex_set_increment (U32 increment)
		297	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		298	$int = $env->mutex_set_max (U32 max)
		299	$int = $env->mutex_set_align (U32 align)
		300
		301	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		302	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		303
		304	=head4 Example:
		305
		306	use AnyEvent;
		307	use BDB;
		308
		309	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		310	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		311
		312	BDB::min_parallel 8;
		313
		314	my $env = db_env_create;
		315
		316	mkdir "bdtest", 0700;
		317	db_env_open
		318	$env,
		319	"bdtest",
		320	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		321	0600;
		322
		323	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		324
		325
		326	=head3 DB/database methods
		327
		328	Methods available on DB/$db handles:
		329
		330	DESTROY (DB_ornull *db)
		331	CODE:
		332	if (db)
		333	{
		334	SV env = (SV )db->app_private;
		335	db->close (db, 0);
		336	SvREFCNT_dec (env);
		337	}
		338
		339	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		340	$int = $db->set_flags (U32 flags)
		341	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		342	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		343	Hash: DUP DUPSORT
		344	Queue: INORDER
		345	Recno: RENUMBER SNAPSHOT
		346
		347	$int = $db->set_encrypt (const char *password, U32 flags)
		348	$int = $db->set_lorder (int lorder)
		349	$int = $db->set_bt_minkey (U32 minkey)
		350	$int = $db->set_re_delim (int delim)
		351	$int = $db->set_re_pad (int re_pad)
		352	$int = $db->set_re_source (char *source)
		353	$int = $db->set_re_len (U32 re_len)
		354	$int = $db->set_h_ffactor (U32 h_ffactor)
		355	$int = $db->set_h_nelem (U32 h_nelem)
		356	$int = $db->set_q_extentsize (U32 extentsize)
		357
		358	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		359	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		360	$seq = $db->sequence (U32 flags = 0)
		361
		362	=head4 Example:
		363
		364	my $db = db_create $env;
		365	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		366
		367	for (1..1000) {
		368	db_put $db, undef, "key $_", "data $_";
		369
		370	db_key_range $db, undef, "key $_", my $keyrange;
		371	my ($lt, $eq, $gt) = @$keyrange;
		372	}
		373
		374	db_del $db, undef, "key $_" for 1..1000;
		375
		376	db_sync $db;
		377
		378
		379	=head3 DB_TXN/transaction methods
		380
		381	Methods available on DB_TXN/$txn handles:
		382
		383	DESTROY (DB_TXN_ornull *txn)
		384	CODE:
		385	if (txn)
		386	txn->abort (txn);
		387
		388	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		389	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		390
		391	$bool = $txn->failed
		392	# see db_txn_finish documentation, above
		393
		394
		395	=head3 DBC/cursor methods
		396
		397	Methods available on DBC/$dbc handles:
		398
		399	DESTROY (DBC_ornull *dbc)
		400	CODE:
		401	if (dbc)
		402	dbc->c_close (dbc);
		403
		404	$int = $cursor->set_priority ($priority = PRIORITY_*)
		405
		406	=head4 Example:
		407
		408	my $c = $db->cursor;
		409
		410	for (;;) {
		411	db_c_get $c, my $key, my $data, BDB::NEXT;
		412	warn "<$!,$key,$data>";
		413	last if $!;
		414	}
		415
		416	db_c_close $c;
		417
		418
		419	=head3 DB_SEQUENCE/sequence methods
		420
		421	Methods available on DB_SEQUENCE/$seq handles:
		422
		423	DESTROY (DB_SEQUENCE_ornull *seq)
		424	CODE:
		425	if (seq)
		426	seq->close (seq, 0);
		427
		428	$int = $seq->initial_value (db_seq_t value)
		429	$int = $seq->set_cachesize (U32 size)
		430	$int = $seq->set_flags (U32 flags)
		431	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		432	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		433
		434	=head4 Example:
		435
		436	my $seq = $db->sequence;
		437
		438	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		439	db_sequence_get $seq, undef, 1, my $value;
		440
		441
80	=head2 SUPPORT FUNCTIONS	442	=head2 SUPPORT FUNCTIONS
81		443
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	444	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		445
84	=over 4	446	=over 4
85		447
		448	=item $msg = BDB::strerror [$errno]
		449
		450	Returns the string corresponding to the given errno value. If no argument
		451	is given, use C<$!>.
		452
		453	Note that the BDB module also patches the C<$!> variable directly, so you
		454	should be able to get a bdb error string by simply stringifying C<$!>.
		455
86	=item $fileno = BDB::AIO::poll_fileno	456	=item $fileno = BDB::poll_fileno
87		457
88	Return the I<request result pipe file descriptor>. This filehandle must be	458	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	459	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	460	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	461	to call C<poll_cb> to check the results.
92		462
93	See C<poll_cb> for an example.	463	See C<poll_cb> for an example.
94		464
95	=item BDB::AIO::poll_cb	465	=item BDB::poll_cb
96		466
97	Process some outstanding events on the result pipe. You have to call this	467	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	468	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	469	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>.	470	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		471
102	If not all requests were processed for whatever reason, the filehandle	472	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	473	will still be ready when C<poll_cb> returns.
104		474
105	Example: Install an Event watcher that automatically calls	475	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	476	BDB::poll_cb with high priority:
107		477
108	Event->io (fd => BDB::AIO::poll_fileno,	478	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	479	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	480	cb => \&BDB::poll_cb);
111		481
112	=item BDB::AIO::max_poll_reqs $nreqs	482	=item BDB::max_poll_reqs $nreqs
113		483
114	=item BDB::AIO::max_poll_time $seconds	484	=item BDB::max_poll_time $seconds
115		485
116	These set the maximum number of requests (default C<0>, meaning infinity)	486	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	487	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	488	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	489	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	490	of time C<poll_cb> is allowed to use).
121		491
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	492	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	493	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	494	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	498	interactiveness when perl is not fast enough to process all requests in
129	time.	499	time.
130		500
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	501	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		502
133	Example: Install an Event watcher that automatically calls	503	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	504	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	505	program get the CPU sometimes even under high load.
136		506
137	# try not to spend much more than 0.1s in poll_cb	507	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	508	BDB::max_poll_time 0.1;
139		509
140	# use a low priority so other tasks have priority	510	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		511
145	=item BDB::AIO::poll_wait	512	=item BDB::poll_wait
146		513
147	If there are any outstanding requests and none of them in the result	514	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	515	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	516	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	517	synchronously wait for some requests to finish).
151		518
152	See C<nreqs> for an example.	519	See C<nreqs> for an example.
153		520
154	=item BDB::AIO::poll	521	=item BDB::poll
155		522
156	Waits until some requests have been handled.	523	Waits until some requests have been handled.
157		524
158	Returns the number of requests processed, but is otherwise strictly	525	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	526	equivalent to:
160		527
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	528	BDB::poll_wait, BDB::poll_cb
162		529
163	=item BDB::AIO::flush	530	=item BDB::flush
164		531
165	Wait till all outstanding AIO requests have been handled.	532	Wait till all outstanding BDB requests have been handled.
166		533
167	Strictly equivalent to:	534	Strictly equivalent to:
168		535
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	536	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	537	while BDB::nreqs;
		538
		539	=back
171		540
172	=head3 CONTROLLING THE NUMBER OF THREADS	541	=head3 CONTROLLING THE NUMBER OF THREADS
173		542
		543	=over 4
		544
174	=item BDB::AIO::min_parallel $nthreads	545	=item BDB::min_parallel $nthreads
175		546
176	Set the minimum number of AIO threads to C<$nthreads>. The current	547	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	548	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	549	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	550	however, is unlimited).
180		551
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	552	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	553	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	554	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.	555	is in the cache and could have been processed faster by a single thread.
185		556
186	It is recommended to keep the number of threads relatively low, as some	557	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	560	versions, 4-32 threads should be fine.
190		561
191	Under most circumstances you don't need to call this function, as the	562	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.	563	module selects a default that is suitable for low to moderate load.
193		564
194	=item BDB::AIO::max_parallel $nthreads	565	=item BDB::max_parallel $nthreads
195		566
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	567	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	568	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	569	them. This function blocks until the limit is reached.
199		570
200	While C<$nthreads> are zero, aio requests get queued but not executed	571	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	572	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	574	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.	575	that all threads are killed and that there are no outstanding requests.
205		576
206	Under normal circumstances you don't need to call this function.	577	Under normal circumstances you don't need to call this function.
207		578
208	=item BDB::AIO::max_idle $nthreads	579	=item BDB::max_idle $nthreads
209		580
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	581	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	582	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	583	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	584	idle, it will free its resources and exit.
…		…
218		589
219	The default is probably ok in most situations, especially if thread	590	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	591	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	592	want to use larger values.
222		593
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	594	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		595
225	This is a very bad function to use in interactive programs because it	596	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	597	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	598	use an C<aio_group> together with a feed callback.
228		599
…		…
236		607
237	You can still queue as many requests as you want. Therefore,	608	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	609	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).	610	as a stop gap to shield against fatal memory overflow (with large values).
240		611
		612	=item BDB::set_sync_prepare $cb
		613
		614	Sets a callback that is called whenever a request is created without an
		615	explicit callback. It has to return two code references. The first is used
		616	as the request callback, and the second is called to wait until the first
		617	callback has been called. The default implementation works like this:
		618
		619	sub {
		620	my $status;
		621	(
		622	sub { $status = $! },
		623	sub { BDB::poll while !defined $status; $! = $status },
		624	)
		625	}
		626
		627	=back
		628
241	=head3 STATISTICAL INFORMATION	629	=head3 STATISTICAL INFORMATION
242		630
		631	=over 4
		632
243	=item BDB::AIO::nreqs	633	=item BDB::nreqs
244		634
245	Returns the number of requests currently in the ready, execute or pending	635	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).	636	states (i.e. for which their callback has not been invoked yet).
247		637
248	Example: wait till there are no outstanding requests anymore:	638	Example: wait till there are no outstanding requests anymore:
249		639
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	640	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	641	while BDB::nreqs;
252		642
253	=item BDB::AIO::nready	643	=item BDB::nready
254		644
255	Returns the number of requests currently in the ready state (not yet	645	Returns the number of requests currently in the ready state (not yet
256	executed).	646	executed).
257		647
258	=item BDB::AIO::npending	648	=item BDB::npending
259		649
260	Returns the number of requests currently in the pending state (executed,	650	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	651	but not yet processed by poll_cb).
262		652
263	=back	653	=back
264		654
265	=cut	655	=cut
266		656
267	# support function to convert a fd into a perl filehandle	657	set_sync_prepare {
268	sub _fd2fh {	658	my $status;
269	return undef if $_[0] < 0;	659	(
270		660	sub {
271	# try to generate nice filehandles	661	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	662	},
273	local *$sym;	663	sub {
274		664	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	665	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	666	},
277	or open *$sym, ">&=$_[0]" # or this	667	)
278	or return undef;	668	};
279
280	*$sym
281	}
282		669
283	min_parallel 8;	670	min_parallel 8;
284		671
285	END { flush }	672	END { flush }
286		673
…		…
288		675
289	=head2 FORK BEHAVIOUR	676	=head2 FORK BEHAVIOUR
290		677
291	This module should do "the right thing" when the process using it forks:	678	This module should do "the right thing" when the process using it forks:
292		679
293	Before the fork, IO::AIO enters a quiescent state where no requests	680	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	681	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	682	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	683	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	684	(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	685	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	686	parent process has been reached again.
300		687
301	In short: the parent will, after a short pause, continue as if fork had	688	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	689	not been called, while the child will act as if BDB has not been used
303	yet.	690	yet.
		691
		692	Win32 note: there is no fork on win32, and perls emulation of it is too
		693	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		694	yet, switch to a more capable platform.
304		695
305	=head2 MEMORY USAGE	696	=head2 MEMORY USAGE
306		697
307	Per-request usage:	698	Per-request usage:
308		699
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	701	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	702	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	703	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.	704	will consume memory till the request has entered the done state.
314		705
315	This is now awfully much, so queuing lots of requests is not usually a	706	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	707	problem.
317		708
318	Per-thread usage:	709	Per-thread usage:
319		710
320	In the execution phase, some aio requests require more memory for	711	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	712	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	713	structures (usually around 16k-128k, depending on the OS).
323		714
324	=head1 KNOWN BUGS	715	=head1 KNOWN BUGS
325		716
326	Known bugs will be fixed in the next release.	717	Known bugs will be fixed in the next release, except:
		718
		719	If you use a transaction in any request, and the request returns
		720	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		721	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		722	above.
327		723
328	=head1 SEE ALSO	724	=head1 SEE ALSO
329		725
330	L<Coro::AIO>.	726	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		727	syntax), L<IO::AIO> (nice to have).
331		728
332	=head1 AUTHOR	729	=head1 AUTHOR
333		730
334	Marc Lehmann <schmorp@schmorp.de>	731	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	732	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 1.36 by root, Sat May 10 20:23:06 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 1.36 by root, Sat May 10 20:23:06 2008 UTC