[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 1.15 by root, Thu Sep 13 21:34:00 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 a Berkeley DB function but a BDB module extension. It is very
		185	annoying to have to check every single BDB function for error returns and
		186	provide a codepath out of your transaction. While the BDB module still
		187	makes this possible, it contains the following extensions:
		188
		189	When a transaction-protected function returns any operating system
		190	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		191	transaction. This flag is also set by Berkeley DB functions externally
		192	when an operation fails with LOCK_DEADLOCK, and it causes all further
		193	operations on that transaction (including C<db_txn_commit>) to fail.
		194
		195	The C<db_txn_finish> request will look at this flag, and, if it is set,
		196	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		197	if it isn't set). If it isn't set, it will call C<db_txn_commit> and
		198	return the error normally.
		199
		200	How to use this? Easy: just write your transaction normally:
		201
		202	my $txn = $db_env->txn_begin;
		203	db_get $db, $txn, "key", my $data;
		204	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		205	db_txn_finish $txn;
		206	die "transaction failed" if $!;
		207
		208	That is, handle only the expected errors. If something unexpected happens
		209	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		210	requests (db_put in this case) will simply be skipped (they will fail with
		211	LOCK_DEADLOCK) and the transaction will be aborted.
		212
		213	You cna use the C<< $txn->failed >> method to check wether a transaction
		214	has failed in this way and abort further processing (excluding
		215	C<db_txn_finish>).
		216
		217	=head3 DB_ENV/database environment methods
		218
		219	Methods available on DB_ENV/$env handles:
		220
		221	DESTROY (DB_ENV_ornull *env)
		222	CODE:
		223	if (env)
		224	env->close (env, 0);
		225
		226	$int = $env->set_data_dir (const char *dir)
		227	$int = $env->set_tmp_dir (const char *dir)
		228	$int = $env->set_lg_dir (const char *dir)
		229	$int = $env->set_shm_key (long shm_key)
		230	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		231	$int = $env->set_flags (U32 flags, int onoff)
		232	$env->set_errfile (FILE *errfile = 0)
		233	$env->set_msgfile (FILE *msgfile = 0)
		234	$int = $env->set_verbose (U32 which, int onoff = 1)
		235	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		236	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		237	$int = $env->set_mp_max_openfd (int maxopenfd);
		238	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		239	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		240	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		241	$int = $env->set_lk_max_lockers (U32 max)
		242	$int = $env->set_lk_max_locks (U32 max)
		243	$int = $env->set_lk_max_objects (U32 max)
		244	$int = $env->set_lg_bsize (U32 max)
		245	$int = $env->set_lg_max (U32 max)
		246
		247	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		248	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		249
		250	=head4 Example:
		251
		252	use AnyEvent;
		253	use BDB;
		254
		255	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		256	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		257
		258	BDB::min_parallel 8;
		259
		260	my $env = db_env_create;
		261
		262	mkdir "bdtest", 0700;
		263	db_env_open
		264	$env,
		265	"bdtest",
		266	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		267	0600;
		268
		269	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		270
		271
		272	=head3 DB/database methods
		273
		274	Methods available on DB/$db handles:
		275
		276	DESTROY (DB_ornull *db)
		277	CODE:
		278	if (db)
		279	{
		280	SV env = (SV )db->app_private;
		281	db->close (db, 0);
		282	SvREFCNT_dec (env);
		283	}
		284
		285	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		286	$int = $db->set_flags (U32 flags)
		287	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		288	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		289	Hash: DUP DUPSORT
		290	Queue: INORDER
		291	Recno: RENUMBER SNAPSHOT
		292
		293	$int = $db->set_encrypt (const char *password, U32 flags)
		294	$int = $db->set_lorder (int lorder)
		295	$int = $db->set_bt_minkey (U32 minkey)
		296	$int = $db->set_re_delim (int delim)
		297	$int = $db->set_re_pad (int re_pad)
		298	$int = $db->set_re_source (char *source)
		299	$int = $db->set_re_len (U32 re_len)
		300	$int = $db->set_h_ffactor (U32 h_ffactor)
		301	$int = $db->set_h_nelem (U32 h_nelem)
		302	$int = $db->set_q_extentsize (U32 extentsize)
		303
		304	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		305	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		306	$seq = $db->sequence (U32 flags = 0)
		307
		308	=head4 Example:
		309
		310	my $db = db_create $env;
		311	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		312
		313	for (1..1000) {
		314	db_put $db, undef, "key $_", "data $_";
		315
		316	db_key_range $db, undef, "key $_", my $keyrange;
		317	my ($lt, $eq, $gt) = @$keyrange;
		318	}
		319
		320	db_del $db, undef, "key $_" for 1..1000;
		321
		322	db_sync $db;
		323
		324
		325	=head3 DB_TXN/transaction methods
		326
		327	Methods available on DB_TXN/$txn handles:
		328
		329	DESTROY (DB_TXN_ornull *txn)
		330	CODE:
		331	if (txn)
		332	txn->abort (txn);
		333
		334	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		335	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		336
		337	$bool = $txn->failed
		338	# see db_txn_finish documentation, above
		339
		340
		341	=head3 DBC/cursor methods
		342
		343	Methods available on DBC/$dbc handles:
		344
		345	DESTROY (DBC_ornull *dbc)
		346	CODE:
		347	if (dbc)
		348	dbc->c_close (dbc);
		349
		350	=head4 Example:
		351
		352	my $c = $db->cursor;
		353
		354	for (;;) {
		355	db_c_get $c, my $key, my $data, BDB::NEXT;
		356	warn "<$!,$key,$data>";
		357	last if $!;
		358	}
		359
		360	db_c_close $c;
		361
		362
		363	=head3 DB_SEQUENCE/sequence methods
		364
		365	Methods available on DB_SEQUENCE/$seq handles:
		366
		367	DESTROY (DB_SEQUENCE_ornull *seq)
		368	CODE:
		369	if (seq)
		370	seq->close (seq, 0);
		371
		372	$int = $seq->initial_value (db_seq_t value)
		373	$int = $seq->set_cachesize (U32 size)
		374	$int = $seq->set_flags (U32 flags)
		375	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		376	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		377
		378	=head4 Example:
		379
		380	my $seq = $db->sequence;
		381
		382	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		383	db_sequence_get $seq, undef, 1, my $value;
		384
		385
80	=head2 SUPPORT FUNCTIONS	386	=head2 SUPPORT FUNCTIONS
81		387
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	388	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		389
84	=over 4	390	=over 4
85		391
86	=item $fileno = BDB::AIO::poll_fileno	392	=item $fileno = BDB::poll_fileno
87		393
88	Return the I<request result pipe file descriptor>. This filehandle must be	394	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	395	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	396	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	397	to call C<poll_cb> to check the results.
92		398
93	See C<poll_cb> for an example.	399	See C<poll_cb> for an example.
94		400
95	=item BDB::AIO::poll_cb	401	=item BDB::poll_cb
96		402
97	Process some outstanding events on the result pipe. You have to call this	403	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	404	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	405	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>.	406	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		407
102	If not all requests were processed for whatever reason, the filehandle	408	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	409	will still be ready when C<poll_cb> returns.
104		410
105	Example: Install an Event watcher that automatically calls	411	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	412	BDB::poll_cb with high priority:
107		413
108	Event->io (fd => BDB::AIO::poll_fileno,	414	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	415	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	416	cb => \&BDB::poll_cb);
111		417
112	=item BDB::AIO::max_poll_reqs $nreqs	418	=item BDB::max_poll_reqs $nreqs
113		419
114	=item BDB::AIO::max_poll_time $seconds	420	=item BDB::max_poll_time $seconds
115		421
116	These set the maximum number of requests (default C<0>, meaning infinity)	422	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	423	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	424	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	425	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	426	of time C<poll_cb> is allowed to use).
121		427
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	428	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	429	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	430	callbacks are really really fast or your OS is really really slow (I am
…		…
129	time.	435	time.
130		436
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	437	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		438
133	Example: Install an Event watcher that automatically calls	439	Example: Install an Event watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	440	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	441	program get the CPU sometimes even under high AIO load.
136		442
137	# try not to spend much more than 0.1s in poll_cb	443	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	444	BDB::max_poll_time 0.1;
139		445
140	# use a low priority so other tasks have priority	446	# use a low priority so other tasks have priority
141	Event->io (fd => BDB::AIO::poll_fileno,	447	Event->io (fd => BDB::poll_fileno,
142	poll => 'r', nice => 1,	448	poll => 'r', nice => 1,
143	cb => &BDB::AIO::poll_cb);	449	cb => &BDB::poll_cb);
144		450
145	=item BDB::AIO::poll_wait	451	=item BDB::poll_wait
146		452
147	If there are any outstanding requests and none of them in the result	453	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	454	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	455	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	456	synchronously wait for some requests to finish).
151		457
152	See C<nreqs> for an example.	458	See C<nreqs> for an example.
153		459
154	=item BDB::AIO::poll	460	=item BDB::poll
155		461
156	Waits until some requests have been handled.	462	Waits until some requests have been handled.
157		463
158	Returns the number of requests processed, but is otherwise strictly	464	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	465	equivalent to:
160		466
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	467	BDB::poll_wait, BDB::poll_cb
162		468
163	=item BDB::AIO::flush	469	=item BDB::flush
164		470
165	Wait till all outstanding AIO requests have been handled.	471	Wait till all outstanding AIO requests have been handled.
166		472
167	Strictly equivalent to:	473	Strictly equivalent to:
168		474
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	475	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	476	while BDB::nreqs;
		477
		478	=back
171		479
172	=head3 CONTROLLING THE NUMBER OF THREADS	480	=head3 CONTROLLING THE NUMBER OF THREADS
173		481
		482	=over 4
		483
174	=item BDB::AIO::min_parallel $nthreads	484	=item BDB::min_parallel $nthreads
175		485
176	Set the minimum number of AIO threads to C<$nthreads>. The current	486	Set the minimum number of AIO threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	487	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	488	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	489	however, is unlimited).
180		490
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	491	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	492	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	493	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.	494	is in the cache and could have been processed faster by a single thread.
185		495
186	It is recommended to keep the number of threads relatively low, as some	496	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	499	versions, 4-32 threads should be fine.
190		500
191	Under most circumstances you don't need to call this function, as the	501	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.	502	module selects a default that is suitable for low to moderate load.
193		503
194	=item BDB::AIO::max_parallel $nthreads	504	=item BDB::max_parallel $nthreads
195		505
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	506	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	507	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	508	them. This function blocks until the limit is reached.
199		509
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	513	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.	514	that all threads are killed and that there are no outstanding requests.
205		515
206	Under normal circumstances you don't need to call this function.	516	Under normal circumstances you don't need to call this function.
207		517
208	=item BDB::AIO::max_idle $nthreads	518	=item BDB::max_idle $nthreads
209		519
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	520	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	521	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	522	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	523	idle, it will free its resources and exit.
…		…
218		528
219	The default is probably ok in most situations, especially if thread	529	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	530	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	531	want to use larger values.
222		532
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	533	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		534
225	This is a very bad function to use in interactive programs because it	535	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	536	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	537	use an C<aio_group> together with a feed callback.
228		538
…		…
236		546
237	You can still queue as many requests as you want. Therefore,	547	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	548	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).	549	as a stop gap to shield against fatal memory overflow (with large values).
240		550
		551	=item BDB::set_sync_prepare $cb
		552
		553	Sets a callback that is called whenever a request is created without an
		554	explicit callback. It has to return two code references. The first is used
		555	as the request callback, and the second is called to wait until the first
		556	callback has been called. The default implementation works like this:
		557
		558	sub {
		559	my $status;
		560	(
		561	sub { $status = $! },
		562	sub { BDB::poll while !defined $status; $! = $status },
		563	)
		564	}
		565
		566	=back
		567
241	=head3 STATISTICAL INFORMATION	568	=head3 STATISTICAL INFORMATION
242		569
		570	=over 4
		571
243	=item BDB::AIO::nreqs	572	=item BDB::nreqs
244		573
245	Returns the number of requests currently in the ready, execute or pending	574	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).	575	states (i.e. for which their callback has not been invoked yet).
247		576
248	Example: wait till there are no outstanding requests anymore:	577	Example: wait till there are no outstanding requests anymore:
249		578
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	579	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	580	while BDB::nreqs;
252		581
253	=item BDB::AIO::nready	582	=item BDB::nready
254		583
255	Returns the number of requests currently in the ready state (not yet	584	Returns the number of requests currently in the ready state (not yet
256	executed).	585	executed).
257		586
258	=item BDB::AIO::npending	587	=item BDB::npending
259		588
260	Returns the number of requests currently in the pending state (executed,	589	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	590	but not yet processed by poll_cb).
262		591
263	=back	592	=back
264		593
265	=cut	594	=cut
266		595
267	# support function to convert a fd into a perl filehandle	596	set_sync_prepare {
268	sub _fd2fh {	597	my $status;
269	return undef if $_[0] < 0;	598	(
270		599	sub {
271	# try to generate nice filehandles	600	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	601	},
273	local *$sym;	602	sub {
274		603	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	604	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	605	},
277	or open *$sym, ">&=$_[0]" # or this	606	)
278	or return undef;	607	};
279
280	*$sym
281	}
282		608
283	min_parallel 8;	609	min_parallel 8;
284		610
285	END { flush }	611	END { flush }
286		612
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	636	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	637	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	638	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.	639	will consume memory till the request has entered the done state.
314		640
315	This is now awfully much, so queuing lots of requests is not usually a	641	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	642	problem.
317		643
318	Per-thread usage:	644	Per-thread usage:
319		645
320	In the execution phase, some aio requests require more memory for	646	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	647	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	648	structures (usually around 16k-128k, depending on the OS).
323		649
324	=head1 KNOWN BUGS	650	=head1 KNOWN BUGS
325		651
326	Known bugs will be fixed in the next release.	652	Known bugs will be fixed in the next release, except:
		653
		654	If you use a transaction in any request, and the request returns
		655	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		656	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		657	above.
327		658
328	=head1 SEE ALSO	659	=head1 SEE ALSO
329		660
330	L<Coro::AIO>.	661	L<Coro::AIO>.
331		662

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Revision 1.15 by root, Thu Sep 13 21:34:00 2007 UTC