[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 1.16 by root, Sun Sep 16 18:17:58 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		8
9	=head1 DESCRIPTION	9	=head1 DESCRIPTION
10		10
11	=head2 EXAMPLE	11	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		12	The BDB API is very similar to the C API (the translation has been very faithful).
		13
		14	See also the example sections in the document below and possibly the eg/
		15	subdirectory of the BDB distribution. Last not least see the IO::AIO
		16	documentation, as that module uses almost the same asynchronous request
		17	model as this module.
		18
		19	I know this is woefully inadequate documentation. Send a patch!
		20
12		21
13	=head1 REQUEST ANATOMY AND LIFETIME	22	=head1 REQUEST ANATOMY AND LIFETIME
14		23
15	Every request method creates a request. which is a C data structure not	24	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	25	directly visible to Perl.
55		64
56	=back	65	=back
57		66
58	=cut	67	=cut
59		68
60	package BDB::AIO;	69	package BDB;
61		70
62	no warnings;	71	no warnings;
63	use strict 'vars';	72	use strict 'vars';
64		73
65	use base 'Exporter';	74	use base 'Exporter';
66		75
67	BEGIN {	76	BEGIN {
68	our $VERSION = '0.1';	77	our $VERSION = '1.1';
69		78
70	our @BDB_REQ = qw();	79	our @BDB_REQ = qw(
		80	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		81	db_env_memp_sync db_env_memp_trickle
		82	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
		83	db_txn_commit db_txn_abort db_txn_finish
		84	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		85	db_sequence_open db_sequence_close
		86	db_sequence_get db_sequence_remove
		87	);
		88	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		89	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	90	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	91	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	92	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	93	max_poll_time max_poll_reqs
		94	);
75		95
76	require XSLoader;	96	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	97	XSLoader::load ("BDB", $VERSION);
78	}	98	}
79		99
		100	=head2 BERKELEYDB FUNCTIONS
		101
		102	All of these are functions. The create functions simply return a new
		103	object and never block. All the remaining functions all take an optional
		104	callback as last argument. If it is missing, then the fucntion will be
		105	executed synchronously.
		106
		107	BDB functions that cannot block (mostly functions that manipulate
		108	settings) are method calls on the relevant objects, so the rule of thumb
		109	is: if its a method, its not blocking, if its a function, it takes a
		110	callback as last argument.
		111
		112	In the following, C<$int> signifies an integer return value,
		113	C<octetstring> is a "binary string" (i.e. a perl string with no character
		114	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		115	integer, C<NV> is a floating point value.
		116
		117	The C<SV *> types are generic perl scalars (for input and output of data
		118	values), and the C<SV *callback> is the optional callback function to call
		119	when the request is completed.
		120
		121	The various C<DB_ENV> etc. arguments are handles return by
		122	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		123	appended C<_ornull> this means they are optional and you can pass C<undef>
		124	for them, resulting a NULL pointer on the C level.
		125
		126	=head3 BDB functions
		127
		128	Functions in the BDB namespace, exported by default:
		129
		130	$env = db_env_create (U32 env_flags = 0)
		131	flags: RPCCLIENT
		132
		133	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		134	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
		135	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		136	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		137	flags: FORCE
		138	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		139	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		140	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		141	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		142
		143	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		144	flags: XA_CREATE
		145
		146	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		147	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		148	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		149	flags: DB_NOSYNC
		150	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)
		151	flags: FREELIST_ONLY FREE_SPACE
		152	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		153	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		154	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		155	flags: APPEND NODUPDATA NOOVERWRITE
		156	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		157	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		158	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		159	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		160	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		161	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		162	flags: TXN_NOSYNC TXN_SYNC
		163	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		164
		165	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		166	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		167	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		168	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		169	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		170	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
		171	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		172	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		173
		174	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		175	flags: CREATE EXCL
		176	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		177	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)
		178	flags: TXN_NOSYNC
		179	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		180	flags: TXN_NOSYNC
		181
		182	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		183
		184	This is not actually a Berkeley DB function but a BDB module
		185	extension. The background for this exytension is: It is very annoying to
		186	have to check every single BDB function for error returns and provide a
		187	codepath out of your transaction. While the BDB module still makes this
		188	possible, it contains the following extensions:
		189
		190	When a transaction-protected function returns any operating system
		191	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		192	transaction. This flag is also set by Berkeley DB functions themselves
		193	when an operation fails with LOCK_DEADLOCK, and it causes all further
		194	operations on that transaction (including C<db_txn_commit>) to fail.
		195
		196	The C<db_txn_finish> request will look at this flag, and, if it is set,
		197	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		198	if it isn't set to something else yet). If it isn't set, it will call
		199	C<db_txn_commit> and return the error normally.
		200
		201	How to use this? Easy: just write your transaction normally:
		202
		203	my $txn = $db_env->txn_begin;
		204	db_get $db, $txn, "key", my $data;
		205	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		206	db_txn_finish $txn;
		207	die "transaction failed" if $!;
		208
		209	That is, handle only the expected errors. If something unexpected happens
		210	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		211	requests (db_put in this case) will simply be skipped (they will fail with
		212	LOCK_DEADLOCK) and the transaction will be aborted.
		213
		214	You can use the C<< $txn->failed >> method to check wether a transaction
		215	has failed in this way and abort further processing (excluding
		216	C<db_txn_finish>).
		217
		218	=head3 DB_ENV/database environment methods
		219
		220	Methods available on DB_ENV/$env handles:
		221
		222	DESTROY (DB_ENV_ornull *env)
		223	CODE:
		224	if (env)
		225	env->close (env, 0);
		226
		227	$int = $env->set_data_dir (const char *dir)
		228	$int = $env->set_tmp_dir (const char *dir)
		229	$int = $env->set_lg_dir (const char *dir)
		230	$int = $env->set_shm_key (long shm_key)
		231	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		232	$int = $env->set_flags (U32 flags, int onoff)
		233	$env->set_errfile (FILE *errfile = 0)
		234	$env->set_msgfile (FILE *msgfile = 0)
		235	$int = $env->set_verbose (U32 which, int onoff = 1)
		236	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		237	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		238	$int = $env->set_mp_max_openfd (int maxopenfd);
		239	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		240	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		241	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		242	$int = $env->set_lk_max_lockers (U32 max)
		243	$int = $env->set_lk_max_locks (U32 max)
		244	$int = $env->set_lk_max_objects (U32 max)
		245	$int = $env->set_lg_bsize (U32 max)
		246	$int = $env->set_lg_max (U32 max)
		247
		248	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		249	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		250
		251	=head4 Example:
		252
		253	use AnyEvent;
		254	use BDB;
		255
		256	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		257	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		258
		259	BDB::min_parallel 8;
		260
		261	my $env = db_env_create;
		262
		263	mkdir "bdtest", 0700;
		264	db_env_open
		265	$env,
		266	"bdtest",
		267	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		268	0600;
		269
		270	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		271
		272
		273	=head3 DB/database methods
		274
		275	Methods available on DB/$db handles:
		276
		277	DESTROY (DB_ornull *db)
		278	CODE:
		279	if (db)
		280	{
		281	SV env = (SV )db->app_private;
		282	db->close (db, 0);
		283	SvREFCNT_dec (env);
		284	}
		285
		286	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		287	$int = $db->set_flags (U32 flags)
		288	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		289	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		290	Hash: DUP DUPSORT
		291	Queue: INORDER
		292	Recno: RENUMBER SNAPSHOT
		293
		294	$int = $db->set_encrypt (const char *password, U32 flags)
		295	$int = $db->set_lorder (int lorder)
		296	$int = $db->set_bt_minkey (U32 minkey)
		297	$int = $db->set_re_delim (int delim)
		298	$int = $db->set_re_pad (int re_pad)
		299	$int = $db->set_re_source (char *source)
		300	$int = $db->set_re_len (U32 re_len)
		301	$int = $db->set_h_ffactor (U32 h_ffactor)
		302	$int = $db->set_h_nelem (U32 h_nelem)
		303	$int = $db->set_q_extentsize (U32 extentsize)
		304
		305	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		306	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		307	$seq = $db->sequence (U32 flags = 0)
		308
		309	=head4 Example:
		310
		311	my $db = db_create $env;
		312	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		313
		314	for (1..1000) {
		315	db_put $db, undef, "key $_", "data $_";
		316
		317	db_key_range $db, undef, "key $_", my $keyrange;
		318	my ($lt, $eq, $gt) = @$keyrange;
		319	}
		320
		321	db_del $db, undef, "key $_" for 1..1000;
		322
		323	db_sync $db;
		324
		325
		326	=head3 DB_TXN/transaction methods
		327
		328	Methods available on DB_TXN/$txn handles:
		329
		330	DESTROY (DB_TXN_ornull *txn)
		331	CODE:
		332	if (txn)
		333	txn->abort (txn);
		334
		335	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		336	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		337
		338	$bool = $txn->failed
		339	# see db_txn_finish documentation, above
		340
		341
		342	=head3 DBC/cursor methods
		343
		344	Methods available on DBC/$dbc handles:
		345
		346	DESTROY (DBC_ornull *dbc)
		347	CODE:
		348	if (dbc)
		349	dbc->c_close (dbc);
		350
		351	=head4 Example:
		352
		353	my $c = $db->cursor;
		354
		355	for (;;) {
		356	db_c_get $c, my $key, my $data, BDB::NEXT;
		357	warn "<$!,$key,$data>";
		358	last if $!;
		359	}
		360
		361	db_c_close $c;
		362
		363
		364	=head3 DB_SEQUENCE/sequence methods
		365
		366	Methods available on DB_SEQUENCE/$seq handles:
		367
		368	DESTROY (DB_SEQUENCE_ornull *seq)
		369	CODE:
		370	if (seq)
		371	seq->close (seq, 0);
		372
		373	$int = $seq->initial_value (db_seq_t value)
		374	$int = $seq->set_cachesize (U32 size)
		375	$int = $seq->set_flags (U32 flags)
		376	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		377	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		378
		379	=head4 Example:
		380
		381	my $seq = $db->sequence;
		382
		383	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		384	db_sequence_get $seq, undef, 1, my $value;
		385
		386
80	=head2 SUPPORT FUNCTIONS	387	=head2 SUPPORT FUNCTIONS
81		388
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	389	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		390
84	=over 4	391	=over 4
85		392
86	=item $fileno = BDB::AIO::poll_fileno	393	=item $fileno = BDB::poll_fileno
87		394
88	Return the I<request result pipe file descriptor>. This filehandle must be	395	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	396	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	397	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	398	to call C<poll_cb> to check the results.
92		399
93	See C<poll_cb> for an example.	400	See C<poll_cb> for an example.
94		401
95	=item BDB::AIO::poll_cb	402	=item BDB::poll_cb
96		403
97	Process some outstanding events on the result pipe. You have to call this	404	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	405	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	406	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>.	407	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		408
102	If not all requests were processed for whatever reason, the filehandle	409	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	410	will still be ready when C<poll_cb> returns.
104		411
105	Example: Install an Event watcher that automatically calls	412	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	413	BDB::poll_cb with high priority:
107		414
108	Event->io (fd => BDB::AIO::poll_fileno,	415	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	416	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	417	cb => \&BDB::poll_cb);
111		418
112	=item BDB::AIO::max_poll_reqs $nreqs	419	=item BDB::max_poll_reqs $nreqs
113		420
114	=item BDB::AIO::max_poll_time $seconds	421	=item BDB::max_poll_time $seconds
115		422
116	These set the maximum number of requests (default C<0>, meaning infinity)	423	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	424	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	425	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	426	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	427	of time C<poll_cb> is allowed to use).
121		428
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	429	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	430	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	431	callbacks are really really fast or your OS is really really slow (I am
…		…
129	time.	436	time.
130		437
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	438	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		439
133	Example: Install an Event watcher that automatically calls	440	Example: Install an Event watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	441	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	442	program get the CPU sometimes even under high AIO load.
136		443
137	# try not to spend much more than 0.1s in poll_cb	444	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	445	BDB::max_poll_time 0.1;
139		446
140	# use a low priority so other tasks have priority	447	# use a low priority so other tasks have priority
141	Event->io (fd => BDB::AIO::poll_fileno,	448	Event->io (fd => BDB::poll_fileno,
142	poll => 'r', nice => 1,	449	poll => 'r', nice => 1,
143	cb => &BDB::AIO::poll_cb);	450	cb => &BDB::poll_cb);
144		451
145	=item BDB::AIO::poll_wait	452	=item BDB::poll_wait
146		453
147	If there are any outstanding requests and none of them in the result	454	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	455	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	456	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	457	synchronously wait for some requests to finish).
151		458
152	See C<nreqs> for an example.	459	See C<nreqs> for an example.
153		460
154	=item BDB::AIO::poll	461	=item BDB::poll
155		462
156	Waits until some requests have been handled.	463	Waits until some requests have been handled.
157		464
158	Returns the number of requests processed, but is otherwise strictly	465	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	466	equivalent to:
160		467
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	468	BDB::poll_wait, BDB::poll_cb
162		469
163	=item BDB::AIO::flush	470	=item BDB::flush
164		471
165	Wait till all outstanding AIO requests have been handled.	472	Wait till all outstanding AIO requests have been handled.
166		473
167	Strictly equivalent to:	474	Strictly equivalent to:
168		475
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	476	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	477	while BDB::nreqs;
		478
		479	=back
171		480
172	=head3 CONTROLLING THE NUMBER OF THREADS	481	=head3 CONTROLLING THE NUMBER OF THREADS
173		482
		483	=over 4
		484
174	=item BDB::AIO::min_parallel $nthreads	485	=item BDB::min_parallel $nthreads
175		486
176	Set the minimum number of AIO threads to C<$nthreads>. The current	487	Set the minimum number of AIO threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	488	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	489	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	490	however, is unlimited).
180		491
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	492	BDB starts threads only on demand, when an AIO request is queued and
182	no free thread exists. Please note that queueing up a hundred requests can	493	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	494	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.	495	is in the cache and could have been processed faster by a single thread.
185		496
186	It is recommended to keep the number of threads relatively low, as some	497	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	500	versions, 4-32 threads should be fine.
190		501
191	Under most circumstances you don't need to call this function, as the	502	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.	503	module selects a default that is suitable for low to moderate load.
193		504
194	=item BDB::AIO::max_parallel $nthreads	505	=item BDB::max_parallel $nthreads
195		506
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	507	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	508	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	509	them. This function blocks until the limit is reached.
199		510
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	514	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.	515	that all threads are killed and that there are no outstanding requests.
205		516
206	Under normal circumstances you don't need to call this function.	517	Under normal circumstances you don't need to call this function.
207		518
208	=item BDB::AIO::max_idle $nthreads	519	=item BDB::max_idle $nthreads
209		520
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	521	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	522	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	523	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	524	idle, it will free its resources and exit.
…		…
218		529
219	The default is probably ok in most situations, especially if thread	530	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	531	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	532	want to use larger values.
222		533
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	534	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		535
225	This is a very bad function to use in interactive programs because it	536	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	537	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	538	use an C<aio_group> together with a feed callback.
228		539
…		…
236		547
237	You can still queue as many requests as you want. Therefore,	548	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	549	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).	550	as a stop gap to shield against fatal memory overflow (with large values).
240		551
		552	=item BDB::set_sync_prepare $cb
		553
		554	Sets a callback that is called whenever a request is created without an
		555	explicit callback. It has to return two code references. The first is used
		556	as the request callback, and the second is called to wait until the first
		557	callback has been called. The default implementation works like this:
		558
		559	sub {
		560	my $status;
		561	(
		562	sub { $status = $! },
		563	sub { BDB::poll while !defined $status; $! = $status },
		564	)
		565	}
		566
		567	=back
		568
241	=head3 STATISTICAL INFORMATION	569	=head3 STATISTICAL INFORMATION
242		570
		571	=over 4
		572
243	=item BDB::AIO::nreqs	573	=item BDB::nreqs
244		574
245	Returns the number of requests currently in the ready, execute or pending	575	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).	576	states (i.e. for which their callback has not been invoked yet).
247		577
248	Example: wait till there are no outstanding requests anymore:	578	Example: wait till there are no outstanding requests anymore:
249		579
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	580	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	581	while BDB::nreqs;
252		582
253	=item BDB::AIO::nready	583	=item BDB::nready
254		584
255	Returns the number of requests currently in the ready state (not yet	585	Returns the number of requests currently in the ready state (not yet
256	executed).	586	executed).
257		587
258	=item BDB::AIO::npending	588	=item BDB::npending
259		589
260	Returns the number of requests currently in the pending state (executed,	590	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	591	but not yet processed by poll_cb).
262		592
263	=back	593	=back
264		594
265	=cut	595	=cut
266		596
267	# support function to convert a fd into a perl filehandle	597	set_sync_prepare {
268	sub _fd2fh {	598	my $status;
269	return undef if $_[0] < 0;	599	(
270		600	sub {
271	# try to generate nice filehandles	601	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	602	},
273	local *$sym;	603	sub {
274		604	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	605	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	606	},
277	or open *$sym, ">&=$_[0]" # or this	607	)
278	or return undef;	608	};
279
280	*$sym
281	}
282		609
283	min_parallel 8;	610	min_parallel 8;
284		611
285	END { flush }	612	END { flush }
286		613
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	637	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	638	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	639	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.	640	will consume memory till the request has entered the done state.
314		641
315	This is now awfully much, so queuing lots of requests is not usually a	642	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	643	problem.
317		644
318	Per-thread usage:	645	Per-thread usage:
319		646
320	In the execution phase, some aio requests require more memory for	647	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	648	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	649	structures (usually around 16k-128k, depending on the OS).
323		650
324	=head1 KNOWN BUGS	651	=head1 KNOWN BUGS
325		652
326	Known bugs will be fixed in the next release.	653	Known bugs will be fixed in the next release, except:
		654
		655	If you use a transaction in any request, and the request returns
		656	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		657	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		658	above.
327		659
328	=head1 SEE ALSO	660	=head1 SEE ALSO
329		661
330	L<Coro::AIO>.	662	L<Coro::AIO>.
331		663

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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 1.16 by root, Sun Sep 16 18:17:58 2007 UTC