[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 1.30 by root, Tue Dec 25 14:23:21 2007 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 = '1.42';
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", $VERSION);
78	}	137	}
79		138
		139	=head2 BERKELEYDB FUNCTIONS
		140
		141	All of these are functions. The create functions simply return a new
		142	object and never block. All the remaining functions all take an optional
		143	callback as last argument. If it is missing, then the function will be
		144	executed synchronously. In both cases, C<$!> 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
80	=head2 SUPPORT FUNCTIONS	434	=head2 SUPPORT FUNCTIONS
81		435
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	436	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		437
84	=over 4	438	=over 4
85		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<$!>.
		444
86	=item $fileno = BDB::AIO::poll_fileno	445	=item $fileno = BDB::poll_fileno
87		446
88	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
89	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
90	select, see below or the SYNOPSIS). If the pipe becomes readable you have	449	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	450	to call C<poll_cb> to check the results.
92		451
93	See C<poll_cb> for an example.	452	See C<poll_cb> for an example.
94		453
95	=item BDB::AIO::poll_cb	454	=item BDB::poll_cb
96		455
97	Process some outstanding events on the result pipe. You have to call this	456	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	457	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	458	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>.	459	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		460
102	If not all requests were processed for whatever reason, the filehandle	461	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	462	will still be ready when C<poll_cb> returns.
104		463
105	Example: Install an Event watcher that automatically calls	464	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	465	BDB::poll_cb with high priority:
107		466
108	Event->io (fd => BDB::AIO::poll_fileno,	467	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	468	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	469	cb => \&BDB::poll_cb);
111		470
112	=item BDB::AIO::max_poll_reqs $nreqs	471	=item BDB::max_poll_reqs $nreqs
113		472
114	=item BDB::AIO::max_poll_time $seconds	473	=item BDB::max_poll_time $seconds
115		474
116	These set the maximum number of requests (default C<0>, meaning infinity)	475	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	476	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	477	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	478	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	479	of time C<poll_cb> is allowed to use).
121		480
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	481	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	482	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	483	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	487	interactiveness when perl is not fast enough to process all requests in
129	time.	488	time.
130		489
131	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.
132		491
133	Example: Install an Event watcher that automatically calls	492	Example: Install an EV watcher that automatically calls
134	BDB::AIO::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
135	program get the CPU sometimes even under high AIO load.	494	program get the CPU sometimes even under high load.
136		495
137	# 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
138	BDB::AIO::max_poll_time 0.1;	497	BDB::max_poll_time 0.1;
139		498
140	# use a low priority so other tasks have priority	499	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		500
145	=item BDB::AIO::poll_wait	501	=item BDB::poll_wait
146		502
147	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
148	phase, wait till the result filehandle becomes ready for reading (simply	504	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	505	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	506	synchronously wait for some requests to finish).
151		507
152	See C<nreqs> for an example.	508	See C<nreqs> for an example.
153		509
154	=item BDB::AIO::poll	510	=item BDB::poll
155		511
156	Waits until some requests have been handled.	512	Waits until some requests have been handled.
157		513
158	Returns the number of requests processed, but is otherwise strictly	514	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	515	equivalent to:
160		516
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	517	BDB::poll_wait, BDB::poll_cb
162		518
163	=item BDB::AIO::flush	519	=item BDB::flush
164		520
165	Wait till all outstanding AIO requests have been handled.	521	Wait till all outstanding BDB requests have been handled.
166		522
167	Strictly equivalent to:	523	Strictly equivalent to:
168		524
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	525	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	526	while BDB::nreqs;
		527
		528	=back
171		529
172	=head3 CONTROLLING THE NUMBER OF THREADS	530	=head3 CONTROLLING THE NUMBER OF THREADS
173		531
		532	=over 4
		533
174	=item BDB::AIO::min_parallel $nthreads	534	=item BDB::min_parallel $nthreads
175		535
176	Set the minimum number of AIO threads to C<$nthreads>. The current	536	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	537	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	538	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	539	however, is unlimited).
180		540
181	BDB::AIO 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
182	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
183	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
184	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.
185		545
186	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
…		…
189	versions, 4-32 threads should be fine.	549	versions, 4-32 threads should be fine.
190		550
191	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
192	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.
193		553
194	=item BDB::AIO::max_parallel $nthreads	554	=item BDB::max_parallel $nthreads
195		555
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	556	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	557	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	558	them. This function blocks until the limit is reached.
199		559
200	While C<$nthreads> are zero, aio requests get queued but not executed	560	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	561	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	563	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.	564	that all threads are killed and that there are no outstanding requests.
205		565
206	Under normal circumstances you don't need to call this function.	566	Under normal circumstances you don't need to call this function.
207		567
208	=item BDB::AIO::max_idle $nthreads	568	=item BDB::max_idle $nthreads
209		569
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	570	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	571	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	572	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	573	idle, it will free its resources and exit.
…		…
218		578
219	The default is probably ok in most situations, especially if thread	579	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	580	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	581	want to use larger values.
222		582
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	583	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		584
225	This is a very bad function to use in interactive programs because it	585	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	586	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	587	use an C<aio_group> together with a feed callback.
228		588
…		…
236		596
237	You can still queue as many requests as you want. Therefore,	597	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	598	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).	599	as a stop gap to shield against fatal memory overflow (with large values).
240		600
		601	=item BDB::set_sync_prepare $cb
		602
		603	Sets a callback that is called whenever a request is created without an
		604	explicit callback. It has to return two code references. The first is used
		605	as the request callback, and the second is called to wait until the first
		606	callback has been called. The default implementation works like this:
		607
		608	sub {
		609	my $status;
		610	(
		611	sub { $status = $! },
		612	sub { BDB::poll while !defined $status; $! = $status },
		613	)
		614	}
		615
		616	=back
		617
241	=head3 STATISTICAL INFORMATION	618	=head3 STATISTICAL INFORMATION
242		619
		620	=over 4
		621
243	=item BDB::AIO::nreqs	622	=item BDB::nreqs
244		623
245	Returns the number of requests currently in the ready, execute or pending	624	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).	625	states (i.e. for which their callback has not been invoked yet).
247		626
248	Example: wait till there are no outstanding requests anymore:	627	Example: wait till there are no outstanding requests anymore:
249		628
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	629	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	630	while BDB::nreqs;
252		631
253	=item BDB::AIO::nready	632	=item BDB::nready
254		633
255	Returns the number of requests currently in the ready state (not yet	634	Returns the number of requests currently in the ready state (not yet
256	executed).	635	executed).
257		636
258	=item BDB::AIO::npending	637	=item BDB::npending
259		638
260	Returns the number of requests currently in the pending state (executed,	639	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	640	but not yet processed by poll_cb).
262		641
263	=back	642	=back
264		643
265	=cut	644	=cut
266		645
267	# support function to convert a fd into a perl filehandle	646	set_sync_prepare {
268	sub _fd2fh {	647	my $status;
269	return undef if $_[0] < 0;	648	(
270		649	sub {
271	# try to generate nice filehandles	650	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	651	},
273	local *$sym;	652	sub {
274		653	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	654	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	655	},
277	or open *$sym, ">&=$_[0]" # or this	656	)
278	or return undef;	657	};
279
280	*$sym
281	}
282		658
283	min_parallel 8;	659	min_parallel 8;
284		660
285	END { flush }	661	END { flush }
286		662
…		…
288		664
289	=head2 FORK BEHAVIOUR	665	=head2 FORK BEHAVIOUR
290		666
291	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:
292		668
293	Before the fork, IO::AIO enters a quiescent state where no requests	669	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	670	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	671	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	672	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	673	(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	674	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	675	parent process has been reached again.
300		676
301	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
302	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
303	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.
304		684
305	=head2 MEMORY USAGE	685	=head2 MEMORY USAGE
306		686
307	Per-request usage:	687	Per-request usage:
308		688
…		…
310	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
311	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
312	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
313	will consume memory till the request has entered the done state.	693	will consume memory till the request has entered the done state.
314		694
315	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
316	problem.	696	problem.
317		697
318	Per-thread usage:	698	Per-thread usage:
319		699
320	In the execution phase, some aio requests require more memory for	700	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	701	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	702	structures (usually around 16k-128k, depending on the OS).
323		703
324	=head1 KNOWN BUGS	704	=head1 KNOWN BUGS
325		705
326	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.
327		712
328	=head1 SEE ALSO	713	=head1 SEE ALSO
329		714
330	L<Coro::AIO>.	715	L<Coro::BDB>, L<IO::AIO>.
331		716
332	=head1 AUTHOR	717	=head1 AUTHOR
333		718
334	Marc Lehmann <schmorp@schmorp.de>	719	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	720	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 1.30 by root, Tue Dec 25 14:23:21 2007 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 1.30 by root, Tue Dec 25 14:23:21 2007 UTC