[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 1.35 by root, Sun Mar 30 08:01:58 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 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
8		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	=head2 EXAMPLE	49	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		50	The BDB API is very similar to the C API (the translation has been very faithful).
		51
		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
12		59
13	=head1 REQUEST ANATOMY AND LIFETIME	60	=head1 REQUEST ANATOMY AND LIFETIME
14		61
15	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
16	directly visible to Perl.	63	directly visible to Perl.
55		102
56	=back	103	=back
57		104
58	=cut	105	=cut
59		106
60	package BDB::AIO;	107	package BDB;
61		108
62	no warnings;	109	no warnings;
63	use strict 'vars';	110	use strict 'vars';
64		111
65	use base 'Exporter';	112	use base 'Exporter';
66		113
67	BEGIN {	114	BEGIN {
68	our $VERSION = '0.1';	115	our $VERSION = '1.45';
69		116
70	our @BDB_REQ = qw();	117	our @BDB_REQ = qw(
		118	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		119	db_env_memp_sync db_env_memp_trickle
		120	db_open db_close db_compact db_sync db_upgrade
		121	db_put db_get db_pget db_del db_key_range
		122	db_txn_commit db_txn_abort db_txn_finish
		123	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		124	db_sequence_open db_sequence_close
		125	db_sequence_get db_sequence_remove
		126	);
		127	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		128	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	129	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	130	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	131	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	132	max_poll_time max_poll_reqs
		133	);
75		134
76	require XSLoader;	135	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	136	XSLoader::load ("BDB", $VERSION);
78	}	137	}
79		138
		139	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		140
		141	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		142	an internal flag to store wether a filename is Unicode or ANSI, but that
		143	flag is used for somethign else in the perl core, so there is no way to
		144	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		145	tries to work around this issue by assuming that the filename is an ANSI
		146	filename and BDB was built for unicode support.
		147
		148	=head2 BERKELEYDB FUNCTIONS
		149
		150	All of these are functions. The create functions simply return a new
		151	object and never block. All the remaining functions take an optional
		152	callback as last argument. If it is missing, then the function will be
		153	executed synchronously. In both cases, C<$!> will reflect the return value
		154	of the function.
		155
		156	BDB functions that cannot block (mostly functions that manipulate
		157	settings) are method calls on the relevant objects, so the rule of thumb
		158	is: if it's a method, it's not blocking, if it's a function, it takes a
		159	callback as last argument.
		160
		161	In the following, C<$int> signifies an integer return value,
		162	C<octetstring> is a "binary string" (i.e. a perl string with no character
		163	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		164	integer, C<NV> is a floating point value.
		165
		166	The C<SV *> types are generic perl scalars (for input and output of data
		167	values), and the C<SV *callback> is the optional callback function to call
		168	when the request is completed.
		169
		170	The various C<DB_ENV> etc. arguments are handles return by
		171	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		172	appended C<_ornull> this means they are optional and you can pass C<undef>
		173	for them, resulting a NULL pointer on the C level.
		174
		175	=head3 BDB functions
		176
		177	Functions in the BDB namespace, exported by default:
		178
		179	$env = db_env_create (U32 env_flags = 0)
		180	flags: RPCCLIENT
		181
		182	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		183	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
		184	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		185	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		186	flags: FORCE
		187	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		188	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		189	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		190	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		191
		192	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		193	flags: XA_CREATE
		194
		195	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		196	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		197	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		198	flags: DB_NOSYNC
		199	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		200	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)
		201	flags: FREELIST_ONLY FREE_SPACE
		202	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		203	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		204	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		205	flags: APPEND NODUPDATA NOOVERWRITE
		206	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		207	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		208	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		209	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		210	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		211	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		212	flags: TXN_NOSYNC TXN_SYNC
		213	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		214
		215	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		216	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		217	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		218	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		219	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		220	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
		221	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		222	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		223
		224	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		225	flags: CREATE EXCL
		226	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		227	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)
		228	flags: TXN_NOSYNC
		229	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		230	flags: TXN_NOSYNC
		231
		232	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		233
		234	This is not actually a Berkeley DB function but a BDB module
		235	extension. The background for this exytension is: It is very annoying to
		236	have to check every single BDB function for error returns and provide a
		237	codepath out of your transaction. While the BDB module still makes this
		238	possible, it contains the following extensions:
		239
		240	When a transaction-protected function returns any operating system
		241	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		242	transaction. This flag is also set by Berkeley DB functions themselves
		243	when an operation fails with LOCK_DEADLOCK, and it causes all further
		244	operations on that transaction (including C<db_txn_commit>) to fail.
		245
		246	The C<db_txn_finish> request will look at this flag, and, if it is set,
		247	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		248	if it isn't set to something else yet). If it isn't set, it will call
		249	C<db_txn_commit> and return the error normally.
		250
		251	How to use this? Easy: just write your transaction normally:
		252
		253	my $txn = $db_env->txn_begin;
		254	db_get $db, $txn, "key", my $data;
		255	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		256	db_txn_finish $txn;
		257	die "transaction failed" if $!;
		258
		259	That is, handle only the expected errors. If something unexpected happens
		260	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		261	requests (db_put in this case) will simply be skipped (they will fail with
		262	LOCK_DEADLOCK) and the transaction will be aborted.
		263
		264	You can use the C<< $txn->failed >> method to check wether a transaction
		265	has failed in this way and abort further processing (excluding
		266	C<db_txn_finish>).
		267
		268	=head3 DB_ENV/database environment methods
		269
		270	Methods available on DB_ENV/$env handles:
		271
		272	DESTROY (DB_ENV_ornull *env)
		273	CODE:
		274	if (env)
		275	env->close (env, 0);
		276
		277	$int = $env->set_data_dir (const char *dir)
		278	$int = $env->set_tmp_dir (const char *dir)
		279	$int = $env->set_lg_dir (const char *dir)
		280	$int = $env->set_shm_key (long shm_key)
		281	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		282	$int = $env->set_flags (U32 flags, int onoff)
		283	$env->set_errfile (FILE *errfile = 0)
		284	$env->set_msgfile (FILE *msgfile = 0)
		285	$int = $env->set_verbose (U32 which, int onoff = 1)
		286	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		287	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		288	$int = $env->set_mp_max_openfd (int maxopenfd);
		289	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		290	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		291	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		292	$int = $env->set_lk_max_lockers (U32 max)
		293	$int = $env->set_lk_max_locks (U32 max)
		294	$int = $env->set_lk_max_objects (U32 max)
		295	$int = $env->set_lg_bsize (U32 max)
		296	$int = $env->set_lg_max (U32 max)
		297	$int = $env->mutex_set_increment (U32 increment)
		298	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		299	$int = $env->mutex_set_max (U32 max)
		300	$int = $env->mutex_set_align (U32 align)
		301
		302	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		303	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		304
		305	=head4 Example:
		306
		307	use AnyEvent;
		308	use BDB;
		309
		310	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		311	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		312
		313	BDB::min_parallel 8;
		314
		315	my $env = db_env_create;
		316
		317	mkdir "bdtest", 0700;
		318	db_env_open
		319	$env,
		320	"bdtest",
		321	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		322	0600;
		323
		324	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		325
		326
		327	=head3 DB/database methods
		328
		329	Methods available on DB/$db handles:
		330
		331	DESTROY (DB_ornull *db)
		332	CODE:
		333	if (db)
		334	{
		335	SV env = (SV )db->app_private;
		336	db->close (db, 0);
		337	SvREFCNT_dec (env);
		338	}
		339
		340	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		341	$int = $db->set_flags (U32 flags)
		342	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		343	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		344	Hash: DUP DUPSORT
		345	Queue: INORDER
		346	Recno: RENUMBER SNAPSHOT
		347
		348	$int = $db->set_encrypt (const char *password, U32 flags)
		349	$int = $db->set_lorder (int lorder)
		350	$int = $db->set_bt_minkey (U32 minkey)
		351	$int = $db->set_re_delim (int delim)
		352	$int = $db->set_re_pad (int re_pad)
		353	$int = $db->set_re_source (char *source)
		354	$int = $db->set_re_len (U32 re_len)
		355	$int = $db->set_h_ffactor (U32 h_ffactor)
		356	$int = $db->set_h_nelem (U32 h_nelem)
		357	$int = $db->set_q_extentsize (U32 extentsize)
		358
		359	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		360	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		361	$seq = $db->sequence (U32 flags = 0)
		362
		363	=head4 Example:
		364
		365	my $db = db_create $env;
		366	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		367
		368	for (1..1000) {
		369	db_put $db, undef, "key $_", "data $_";
		370
		371	db_key_range $db, undef, "key $_", my $keyrange;
		372	my ($lt, $eq, $gt) = @$keyrange;
		373	}
		374
		375	db_del $db, undef, "key $_" for 1..1000;
		376
		377	db_sync $db;
		378
		379
		380	=head3 DB_TXN/transaction methods
		381
		382	Methods available on DB_TXN/$txn handles:
		383
		384	DESTROY (DB_TXN_ornull *txn)
		385	CODE:
		386	if (txn)
		387	txn->abort (txn);
		388
		389	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		390	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		391
		392	$bool = $txn->failed
		393	# see db_txn_finish documentation, above
		394
		395
		396	=head3 DBC/cursor methods
		397
		398	Methods available on DBC/$dbc handles:
		399
		400	DESTROY (DBC_ornull *dbc)
		401	CODE:
		402	if (dbc)
		403	dbc->c_close (dbc);
		404
		405	$int = $cursor->set_priority ($priority = PRIORITY_*)
		406
		407	=head4 Example:
		408
		409	my $c = $db->cursor;
		410
		411	for (;;) {
		412	db_c_get $c, my $key, my $data, BDB::NEXT;
		413	warn "<$!,$key,$data>";
		414	last if $!;
		415	}
		416
		417	db_c_close $c;
		418
		419
		420	=head3 DB_SEQUENCE/sequence methods
		421
		422	Methods available on DB_SEQUENCE/$seq handles:
		423
		424	DESTROY (DB_SEQUENCE_ornull *seq)
		425	CODE:
		426	if (seq)
		427	seq->close (seq, 0);
		428
		429	$int = $seq->initial_value (db_seq_t value)
		430	$int = $seq->set_cachesize (U32 size)
		431	$int = $seq->set_flags (U32 flags)
		432	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		433	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		434
		435	=head4 Example:
		436
		437	my $seq = $db->sequence;
		438
		439	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		440	db_sequence_get $seq, undef, 1, my $value;
		441
		442
80	=head2 SUPPORT FUNCTIONS	443	=head2 SUPPORT FUNCTIONS
81		444
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	445	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		446
84	=over 4	447	=over 4
85		448
		449	=item $msg = BDB::strerror [$errno]
		450
		451	Returns the string corresponding to the given errno value. If no argument
		452	is given, use C<$!>.
		453
		454	Note that the BDB module also patches the C<$!> variable directly, so you
		455	should be able to get a bdb error string by simply stringifying C<$!>.
		456
86	=item $fileno = BDB::AIO::poll_fileno	457	=item $fileno = BDB::poll_fileno
87		458
88	Return the I<request result pipe file descriptor>. This filehandle must be	459	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	460	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	461	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	462	to call C<poll_cb> to check the results.
92		463
93	See C<poll_cb> for an example.	464	See C<poll_cb> for an example.
94		465
95	=item BDB::AIO::poll_cb	466	=item BDB::poll_cb
96		467
97	Process some outstanding events on the result pipe. You have to call this	468	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	469	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	470	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>.	471	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		472
102	If not all requests were processed for whatever reason, the filehandle	473	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	474	will still be ready when C<poll_cb> returns.
104		475
105	Example: Install an Event watcher that automatically calls	476	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	477	BDB::poll_cb with high priority:
107		478
108	Event->io (fd => BDB::AIO::poll_fileno,	479	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	480	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	481	cb => \&BDB::poll_cb);
111		482
112	=item BDB::AIO::max_poll_reqs $nreqs	483	=item BDB::max_poll_reqs $nreqs
113		484
114	=item BDB::AIO::max_poll_time $seconds	485	=item BDB::max_poll_time $seconds
115		486
116	These set the maximum number of requests (default C<0>, meaning infinity)	487	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	488	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	489	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	490	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	491	of time C<poll_cb> is allowed to use).
121		492
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	493	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	494	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	495	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	499	interactiveness when perl is not fast enough to process all requests in
129	time.	500	time.
130		501
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	502	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		503
133	Example: Install an Event watcher that automatically calls	504	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	505	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	506	program get the CPU sometimes even under high load.
136		507
137	# try not to spend much more than 0.1s in poll_cb	508	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	509	BDB::max_poll_time 0.1;
139		510
140	# use a low priority so other tasks have priority	511	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		512
145	=item BDB::AIO::poll_wait	513	=item BDB::poll_wait
146		514
147	If there are any outstanding requests and none of them in the result	515	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	516	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	517	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	518	synchronously wait for some requests to finish).
151		519
152	See C<nreqs> for an example.	520	See C<nreqs> for an example.
153		521
154	=item BDB::AIO::poll	522	=item BDB::poll
155		523
156	Waits until some requests have been handled.	524	Waits until some requests have been handled.
157		525
158	Returns the number of requests processed, but is otherwise strictly	526	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	527	equivalent to:
160		528
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	529	BDB::poll_wait, BDB::poll_cb
162		530
163	=item BDB::AIO::flush	531	=item BDB::flush
164		532
165	Wait till all outstanding AIO requests have been handled.	533	Wait till all outstanding BDB requests have been handled.
166		534
167	Strictly equivalent to:	535	Strictly equivalent to:
168		536
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	537	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	538	while BDB::nreqs;
		539
		540	=back
171		541
172	=head3 CONTROLLING THE NUMBER OF THREADS	542	=head3 CONTROLLING THE NUMBER OF THREADS
173		543
		544	=over 4
		545
174	=item BDB::AIO::min_parallel $nthreads	546	=item BDB::min_parallel $nthreads
175		547
176	Set the minimum number of AIO threads to C<$nthreads>. The current	548	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	549	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	550	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	551	however, is unlimited).
180		552
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	553	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	554	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	555	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.	556	is in the cache and could have been processed faster by a single thread.
185		557
186	It is recommended to keep the number of threads relatively low, as some	558	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	561	versions, 4-32 threads should be fine.
190		562
191	Under most circumstances you don't need to call this function, as the	563	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.	564	module selects a default that is suitable for low to moderate load.
193		565
194	=item BDB::AIO::max_parallel $nthreads	566	=item BDB::max_parallel $nthreads
195		567
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	568	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	569	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	570	them. This function blocks until the limit is reached.
199		571
200	While C<$nthreads> are zero, aio requests get queued but not executed	572	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	573	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	575	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.	576	that all threads are killed and that there are no outstanding requests.
205		577
206	Under normal circumstances you don't need to call this function.	578	Under normal circumstances you don't need to call this function.
207		579
208	=item BDB::AIO::max_idle $nthreads	580	=item BDB::max_idle $nthreads
209		581
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	582	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	583	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	584	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	585	idle, it will free its resources and exit.
…		…
218		590
219	The default is probably ok in most situations, especially if thread	591	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	592	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	593	want to use larger values.
222		594
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	595	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		596
225	This is a very bad function to use in interactive programs because it	597	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	598	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	599	use an C<aio_group> together with a feed callback.
228		600
…		…
236		608
237	You can still queue as many requests as you want. Therefore,	609	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	610	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).	611	as a stop gap to shield against fatal memory overflow (with large values).
240		612
		613	=item BDB::set_sync_prepare $cb
		614
		615	Sets a callback that is called whenever a request is created without an
		616	explicit callback. It has to return two code references. The first is used
		617	as the request callback, and the second is called to wait until the first
		618	callback has been called. The default implementation works like this:
		619
		620	sub {
		621	my $status;
		622	(
		623	sub { $status = $! },
		624	sub { BDB::poll while !defined $status; $! = $status },
		625	)
		626	}
		627
		628	=back
		629
241	=head3 STATISTICAL INFORMATION	630	=head3 STATISTICAL INFORMATION
242		631
		632	=over 4
		633
243	=item BDB::AIO::nreqs	634	=item BDB::nreqs
244		635
245	Returns the number of requests currently in the ready, execute or pending	636	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).	637	states (i.e. for which their callback has not been invoked yet).
247		638
248	Example: wait till there are no outstanding requests anymore:	639	Example: wait till there are no outstanding requests anymore:
249		640
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	641	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	642	while BDB::nreqs;
252		643
253	=item BDB::AIO::nready	644	=item BDB::nready
254		645
255	Returns the number of requests currently in the ready state (not yet	646	Returns the number of requests currently in the ready state (not yet
256	executed).	647	executed).
257		648
258	=item BDB::AIO::npending	649	=item BDB::npending
259		650
260	Returns the number of requests currently in the pending state (executed,	651	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	652	but not yet processed by poll_cb).
262		653
263	=back	654	=back
264		655
265	=cut	656	=cut
266		657
267	# support function to convert a fd into a perl filehandle	658	set_sync_prepare {
268	sub _fd2fh {	659	my $status;
269	return undef if $_[0] < 0;	660	(
270		661	sub {
271	# try to generate nice filehandles	662	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	663	},
273	local *$sym;	664	sub {
274		665	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	666	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	667	},
277	or open *$sym, ">&=$_[0]" # or this	668	)
278	or return undef;	669	};
279
280	*$sym
281	}
282		670
283	min_parallel 8;	671	min_parallel 8;
284		672
285	END { flush }	673	END { flush }
286		674
…		…
288		676
289	=head2 FORK BEHAVIOUR	677	=head2 FORK BEHAVIOUR
290		678
291	This module should do "the right thing" when the process using it forks:	679	This module should do "the right thing" when the process using it forks:
292		680
293	Before the fork, IO::AIO enters a quiescent state where no requests	681	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	682	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	683	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	684	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	685	(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	686	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	687	parent process has been reached again.
300		688
301	In short: the parent will, after a short pause, continue as if fork had	689	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	690	not been called, while the child will act as if BDB has not been used
303	yet.	691	yet.
		692
		693	Win32 note: there is no fork on win32, and perls emulation of it is too
		694	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		695	yet, switch to a more capable platform.
304		696
305	=head2 MEMORY USAGE	697	=head2 MEMORY USAGE
306		698
307	Per-request usage:	699	Per-request usage:
308		700
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	702	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	703	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	704	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.	705	will consume memory till the request has entered the done state.
314		706
315	This is now awfully much, so queuing lots of requests is not usually a	707	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	708	problem.
317		709
318	Per-thread usage:	710	Per-thread usage:
319		711
320	In the execution phase, some aio requests require more memory for	712	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	713	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	714	structures (usually around 16k-128k, depending on the OS).
323		715
324	=head1 KNOWN BUGS	716	=head1 KNOWN BUGS
325		717
326	Known bugs will be fixed in the next release.	718	Known bugs will be fixed in the next release, except:
		719
		720	If you use a transaction in any request, and the request returns
		721	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		722	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		723	above.
327		724
328	=head1 SEE ALSO	725	=head1 SEE ALSO
329		726
330	L<Coro::AIO>.	727	L<Coro::BDB>, L<IO::AIO>.
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/

Diff Legend

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

Comparing BDB/BDB.pm (file contents): Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs. Revision 1.35 by root, Sun Mar 30 08:01:58 2008 UTC

Diff Legend

Comparing BDB/BDB.pm (file contents):
Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.35 by root, Sun Mar 30 08:01:58 2008 UTC