[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 1.25 by root, Mon Dec 10 21:19:06 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	# automatic result processing with AnyEvent:
		30	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		31	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		32
		33	# automatic result processing with EV:
		34	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		35
		36	# with Glib:
		37	add_watch Glib::IO BDB::poll_fileno,
		38	in => sub { BDB::poll_cb; 1 };
		39
		40	# or simply flush manually
		41	BDB::flush;
		42
8		43
9	=head1 DESCRIPTION	44	=head1 DESCRIPTION
10		45
11	=head2 EXAMPLE	46	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		47	The BDB API is very similar to the C API (the translation has been very faithful).
		48
		49	See also the example sections in the document below and possibly the eg/
		50	subdirectory of the BDB distribution. Last not least see the IO::AIO
		51	documentation, as that module uses almost the same asynchronous request
		52	model as this module.
		53
		54	I know this is woefully inadequate documentation. Send a patch!
		55
12		56
13	=head1 REQUEST ANATOMY AND LIFETIME	57	=head1 REQUEST ANATOMY AND LIFETIME
14		58
15	Every request method creates a request. which is a C data structure not	59	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	60	directly visible to Perl.
55		99
56	=back	100	=back
57		101
58	=cut	102	=cut
59		103
60	package BDB::AIO;	104	package BDB;
61		105
62	no warnings;	106	no warnings;
63	use strict 'vars';	107	use strict 'vars';
64		108
65	use base 'Exporter';	109	use base 'Exporter';
66		110
67	BEGIN {	111	BEGIN {
68	our $VERSION = '0.1';	112	our $VERSION = '1.3';
69		113
70	our @BDB_REQ = qw();	114	our @BDB_REQ = qw(
		115	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		116	db_env_memp_sync db_env_memp_trickle
		117	db_open db_close db_compact db_sync db_upgrade
		118	db_put db_get db_pget db_del db_key_range
		119	db_txn_commit db_txn_abort db_txn_finish
		120	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		121	db_sequence_open db_sequence_close
		122	db_sequence_get db_sequence_remove
		123	);
		124	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		125	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	126	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	127	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	128	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	129	max_poll_time max_poll_reqs
		130	);
75		131
76	require XSLoader;	132	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	133	XSLoader::load ("BDB", $VERSION);
78	}	134	}
79		135
		136	=head2 BERKELEYDB FUNCTIONS
		137
		138	All of these are functions. The create functions simply return a new
		139	object and never block. All the remaining functions all take an optional
		140	callback as last argument. If it is missing, then the function will be
		141	executed synchronously. In both cases, C<$!> will reflect the return value
		142	of the function.
		143
		144	BDB functions that cannot block (mostly functions that manipulate
		145	settings) are method calls on the relevant objects, so the rule of thumb
		146	is: if its a method, its not blocking, if its a function, it takes a
		147	callback as last argument.
		148
		149	In the following, C<$int> signifies an integer return value,
		150	C<octetstring> is a "binary string" (i.e. a perl string with no character
		151	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		152	integer, C<NV> is a floating point value.
		153
		154	The C<SV *> types are generic perl scalars (for input and output of data
		155	values), and the C<SV *callback> is the optional callback function to call
		156	when the request is completed.
		157
		158	The various C<DB_ENV> etc. arguments are handles return by
		159	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		160	appended C<_ornull> this means they are optional and you can pass C<undef>
		161	for them, resulting a NULL pointer on the C level.
		162
		163	=head3 BDB functions
		164
		165	Functions in the BDB namespace, exported by default:
		166
		167	$env = db_env_create (U32 env_flags = 0)
		168	flags: RPCCLIENT
		169
		170	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		171	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
		172	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		173	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		174	flags: FORCE
		175	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		176	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		177	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		178	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		179
		180	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		181	flags: XA_CREATE
		182
		183	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		184	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		185	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		186	flags: DB_NOSYNC
		187	db_upgrade (DB db, octetstring file, U32 flags = 0, SV callback = &PL_sv_undef)
		188	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)
		189	flags: FREELIST_ONLY FREE_SPACE
		190	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		191	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		192	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		193	flags: APPEND NODUPDATA NOOVERWRITE
		194	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		195	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		196	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		197	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		198	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		199	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		200	flags: TXN_NOSYNC TXN_SYNC
		201	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		202
		203	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		204	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		205	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		206	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		207	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		208	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
		209	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		210	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		211
		212	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		213	flags: CREATE EXCL
		214	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		215	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)
		216	flags: TXN_NOSYNC
		217	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		218	flags: TXN_NOSYNC
		219
		220	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		221
		222	This is not actually a Berkeley DB function but a BDB module
		223	extension. The background for this exytension is: It is very annoying to
		224	have to check every single BDB function for error returns and provide a
		225	codepath out of your transaction. While the BDB module still makes this
		226	possible, it contains the following extensions:
		227
		228	When a transaction-protected function returns any operating system
		229	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		230	transaction. This flag is also set by Berkeley DB functions themselves
		231	when an operation fails with LOCK_DEADLOCK, and it causes all further
		232	operations on that transaction (including C<db_txn_commit>) to fail.
		233
		234	The C<db_txn_finish> request will look at this flag, and, if it is set,
		235	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		236	if it isn't set to something else yet). If it isn't set, it will call
		237	C<db_txn_commit> and return the error normally.
		238
		239	How to use this? Easy: just write your transaction normally:
		240
		241	my $txn = $db_env->txn_begin;
		242	db_get $db, $txn, "key", my $data;
		243	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		244	db_txn_finish $txn;
		245	die "transaction failed" if $!;
		246
		247	That is, handle only the expected errors. If something unexpected happens
		248	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		249	requests (db_put in this case) will simply be skipped (they will fail with
		250	LOCK_DEADLOCK) and the transaction will be aborted.
		251
		252	You can use the C<< $txn->failed >> method to check wether a transaction
		253	has failed in this way and abort further processing (excluding
		254	C<db_txn_finish>).
		255
		256	=head3 DB_ENV/database environment methods
		257
		258	Methods available on DB_ENV/$env handles:
		259
		260	DESTROY (DB_ENV_ornull *env)
		261	CODE:
		262	if (env)
		263	env->close (env, 0);
		264
		265	$int = $env->set_data_dir (const char *dir)
		266	$int = $env->set_tmp_dir (const char *dir)
		267	$int = $env->set_lg_dir (const char *dir)
		268	$int = $env->set_shm_key (long shm_key)
		269	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		270	$int = $env->set_flags (U32 flags, int onoff)
		271	$env->set_errfile (FILE *errfile = 0)
		272	$env->set_msgfile (FILE *msgfile = 0)
		273	$int = $env->set_verbose (U32 which, int onoff = 1)
		274	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		275	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		276	$int = $env->set_mp_max_openfd (int maxopenfd);
		277	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		278	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		279	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		280	$int = $env->set_lk_max_lockers (U32 max)
		281	$int = $env->set_lk_max_locks (U32 max)
		282	$int = $env->set_lk_max_objects (U32 max)
		283	$int = $env->set_lg_bsize (U32 max)
		284	$int = $env->set_lg_max (U32 max)
		285	$int = $env->mutex_set_increment (U32 increment)
		286	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		287	$int = $env->mutex_set_max (U32 max)
		288	$int = $env->mutex_set_align (U32 align)
		289
		290	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		291	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		292
		293	=head4 Example:
		294
		295	use AnyEvent;
		296	use BDB;
		297
		298	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		299	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		300
		301	BDB::min_parallel 8;
		302
		303	my $env = db_env_create;
		304
		305	mkdir "bdtest", 0700;
		306	db_env_open
		307	$env,
		308	"bdtest",
		309	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		310	0600;
		311
		312	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		313
		314
		315	=head3 DB/database methods
		316
		317	Methods available on DB/$db handles:
		318
		319	DESTROY (DB_ornull *db)
		320	CODE:
		321	if (db)
		322	{
		323	SV env = (SV )db->app_private;
		324	db->close (db, 0);
		325	SvREFCNT_dec (env);
		326	}
		327
		328	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		329	$int = $db->set_flags (U32 flags)
		330	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		331	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		332	Hash: DUP DUPSORT
		333	Queue: INORDER
		334	Recno: RENUMBER SNAPSHOT
		335
		336	$int = $db->set_encrypt (const char *password, U32 flags)
		337	$int = $db->set_lorder (int lorder)
		338	$int = $db->set_bt_minkey (U32 minkey)
		339	$int = $db->set_re_delim (int delim)
		340	$int = $db->set_re_pad (int re_pad)
		341	$int = $db->set_re_source (char *source)
		342	$int = $db->set_re_len (U32 re_len)
		343	$int = $db->set_h_ffactor (U32 h_ffactor)
		344	$int = $db->set_h_nelem (U32 h_nelem)
		345	$int = $db->set_q_extentsize (U32 extentsize)
		346
		347	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		348	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		349	$seq = $db->sequence (U32 flags = 0)
		350
		351	=head4 Example:
		352
		353	my $db = db_create $env;
		354	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		355
		356	for (1..1000) {
		357	db_put $db, undef, "key $_", "data $_";
		358
		359	db_key_range $db, undef, "key $_", my $keyrange;
		360	my ($lt, $eq, $gt) = @$keyrange;
		361	}
		362
		363	db_del $db, undef, "key $_" for 1..1000;
		364
		365	db_sync $db;
		366
		367
		368	=head3 DB_TXN/transaction methods
		369
		370	Methods available on DB_TXN/$txn handles:
		371
		372	DESTROY (DB_TXN_ornull *txn)
		373	CODE:
		374	if (txn)
		375	txn->abort (txn);
		376
		377	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		378	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		379
		380	$bool = $txn->failed
		381	# see db_txn_finish documentation, above
		382
		383
		384	=head3 DBC/cursor methods
		385
		386	Methods available on DBC/$dbc handles:
		387
		388	DESTROY (DBC_ornull *dbc)
		389	CODE:
		390	if (dbc)
		391	dbc->c_close (dbc);
		392
		393	=head4 Example:
		394
		395	my $c = $db->cursor;
		396
		397	for (;;) {
		398	db_c_get $c, my $key, my $data, BDB::NEXT;
		399	warn "<$!,$key,$data>";
		400	last if $!;
		401	}
		402
		403	db_c_close $c;
		404
		405
		406	=head3 DB_SEQUENCE/sequence methods
		407
		408	Methods available on DB_SEQUENCE/$seq handles:
		409
		410	DESTROY (DB_SEQUENCE_ornull *seq)
		411	CODE:
		412	if (seq)
		413	seq->close (seq, 0);
		414
		415	$int = $seq->initial_value (db_seq_t value)
		416	$int = $seq->set_cachesize (U32 size)
		417	$int = $seq->set_flags (U32 flags)
		418	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		419	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		420
		421	=head4 Example:
		422
		423	my $seq = $db->sequence;
		424
		425	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		426	db_sequence_get $seq, undef, 1, my $value;
		427
		428
80	=head2 SUPPORT FUNCTIONS	429	=head2 SUPPORT FUNCTIONS
81		430
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	431	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		432
84	=over 4	433	=over 4
85		434
		435	=item $msg = BDB::strerror [$errno]
		436
		437	Returns the string corresponding to the given errno value. If no argument
		438	is given, use C<$!>.
		439
86	=item $fileno = BDB::AIO::poll_fileno	440	=item $fileno = BDB::poll_fileno
87		441
88	Return the I<request result pipe file descriptor>. This filehandle must be	442	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	443	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	444	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	445	to call C<poll_cb> to check the results.
92		446
93	See C<poll_cb> for an example.	447	See C<poll_cb> for an example.
94		448
95	=item BDB::AIO::poll_cb	449	=item BDB::poll_cb
96		450
97	Process some outstanding events on the result pipe. You have to call this	451	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	452	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	453	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>.	454	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		455
102	If not all requests were processed for whatever reason, the filehandle	456	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	457	will still be ready when C<poll_cb> returns.
104		458
105	Example: Install an Event watcher that automatically calls	459	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	460	BDB::poll_cb with high priority:
107		461
108	Event->io (fd => BDB::AIO::poll_fileno,	462	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	463	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	464	cb => \&BDB::poll_cb);
111		465
112	=item BDB::AIO::max_poll_reqs $nreqs	466	=item BDB::max_poll_reqs $nreqs
113		467
114	=item BDB::AIO::max_poll_time $seconds	468	=item BDB::max_poll_time $seconds
115		469
116	These set the maximum number of requests (default C<0>, meaning infinity)	470	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	471	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	472	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	473	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	474	of time C<poll_cb> is allowed to use).
121		475
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	476	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	477	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	478	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	482	interactiveness when perl is not fast enough to process all requests in
129	time.	483	time.
130		484
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	485	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		486
133	Example: Install an Event watcher that automatically calls	487	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	488	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	489	program get the CPU sometimes even under high load.
136		490
137	# try not to spend much more than 0.1s in poll_cb	491	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	492	BDB::max_poll_time 0.1;
139		493
140	# use a low priority so other tasks have priority	494	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		495
145	=item BDB::AIO::poll_wait	496	=item BDB::poll_wait
146		497
147	If there are any outstanding requests and none of them in the result	498	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	499	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	500	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	501	synchronously wait for some requests to finish).
151		502
152	See C<nreqs> for an example.	503	See C<nreqs> for an example.
153		504
154	=item BDB::AIO::poll	505	=item BDB::poll
155		506
156	Waits until some requests have been handled.	507	Waits until some requests have been handled.
157		508
158	Returns the number of requests processed, but is otherwise strictly	509	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	510	equivalent to:
160		511
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	512	BDB::poll_wait, BDB::poll_cb
162		513
163	=item BDB::AIO::flush	514	=item BDB::flush
164		515
165	Wait till all outstanding AIO requests have been handled.	516	Wait till all outstanding BDB requests have been handled.
166		517
167	Strictly equivalent to:	518	Strictly equivalent to:
168		519
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	520	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	521	while BDB::nreqs;
		522
		523	=back
171		524
172	=head3 CONTROLLING THE NUMBER OF THREADS	525	=head3 CONTROLLING THE NUMBER OF THREADS
173		526
		527	=over 4
		528
174	=item BDB::AIO::min_parallel $nthreads	529	=item BDB::min_parallel $nthreads
175		530
176	Set the minimum number of AIO threads to C<$nthreads>. The current	531	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	532	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	533	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	534	however, is unlimited).
180		535
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	536	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	537	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	538	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.	539	is in the cache and could have been processed faster by a single thread.
185		540
186	It is recommended to keep the number of threads relatively low, as some	541	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	544	versions, 4-32 threads should be fine.
190		545
191	Under most circumstances you don't need to call this function, as the	546	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.	547	module selects a default that is suitable for low to moderate load.
193		548
194	=item BDB::AIO::max_parallel $nthreads	549	=item BDB::max_parallel $nthreads
195		550
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	551	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	552	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	553	them. This function blocks until the limit is reached.
199		554
200	While C<$nthreads> are zero, aio requests get queued but not executed	555	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	556	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	558	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.	559	that all threads are killed and that there are no outstanding requests.
205		560
206	Under normal circumstances you don't need to call this function.	561	Under normal circumstances you don't need to call this function.
207		562
208	=item BDB::AIO::max_idle $nthreads	563	=item BDB::max_idle $nthreads
209		564
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	565	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	566	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	567	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	568	idle, it will free its resources and exit.
…		…
218		573
219	The default is probably ok in most situations, especially if thread	574	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	575	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	576	want to use larger values.
222		577
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	578	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		579
225	This is a very bad function to use in interactive programs because it	580	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	581	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	582	use an C<aio_group> together with a feed callback.
228		583
…		…
236		591
237	You can still queue as many requests as you want. Therefore,	592	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	593	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).	594	as a stop gap to shield against fatal memory overflow (with large values).
240		595
		596	=item BDB::set_sync_prepare $cb
		597
		598	Sets a callback that is called whenever a request is created without an
		599	explicit callback. It has to return two code references. The first is used
		600	as the request callback, and the second is called to wait until the first
		601	callback has been called. The default implementation works like this:
		602
		603	sub {
		604	my $status;
		605	(
		606	sub { $status = $! },
		607	sub { BDB::poll while !defined $status; $! = $status },
		608	)
		609	}
		610
		611	=back
		612
241	=head3 STATISTICAL INFORMATION	613	=head3 STATISTICAL INFORMATION
242		614
		615	=over 4
		616
243	=item BDB::AIO::nreqs	617	=item BDB::nreqs
244		618
245	Returns the number of requests currently in the ready, execute or pending	619	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).	620	states (i.e. for which their callback has not been invoked yet).
247		621
248	Example: wait till there are no outstanding requests anymore:	622	Example: wait till there are no outstanding requests anymore:
249		623
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	624	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	625	while BDB::nreqs;
252		626
253	=item BDB::AIO::nready	627	=item BDB::nready
254		628
255	Returns the number of requests currently in the ready state (not yet	629	Returns the number of requests currently in the ready state (not yet
256	executed).	630	executed).
257		631
258	=item BDB::AIO::npending	632	=item BDB::npending
259		633
260	Returns the number of requests currently in the pending state (executed,	634	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	635	but not yet processed by poll_cb).
262		636
263	=back	637	=back
264		638
265	=cut	639	=cut
266		640
267	# support function to convert a fd into a perl filehandle	641	set_sync_prepare {
268	sub _fd2fh {	642	my $status;
269	return undef if $_[0] < 0;	643	(
270		644	sub {
271	# try to generate nice filehandles	645	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	646	},
273	local *$sym;	647	sub {
274		648	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	649	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	650	},
277	or open *$sym, ">&=$_[0]" # or this	651	)
278	or return undef;	652	};
279
280	*$sym
281	}
282		653
283	min_parallel 8;	654	min_parallel 8;
284		655
285	END { flush }	656	END { flush }
286		657
…		…
288		659
289	=head2 FORK BEHAVIOUR	660	=head2 FORK BEHAVIOUR
290		661
291	This module should do "the right thing" when the process using it forks:	662	This module should do "the right thing" when the process using it forks:
292		663
293	Before the fork, IO::AIO enters a quiescent state where no requests	664	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	665	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	666	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	667	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	668	(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	669	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	670	parent process has been reached again.
300		671
301	In short: the parent will, after a short pause, continue as if fork had	672	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	673	not been called, while the child will act as if BDB has not been used
303	yet.	674	yet.
304		675
305	=head2 MEMORY USAGE	676	=head2 MEMORY USAGE
306		677
307	Per-request usage:	678	Per-request usage:
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	681	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	682	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	683	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.	684	will consume memory till the request has entered the done state.
314		685
315	This is now awfully much, so queuing lots of requests is not usually a	686	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	687	problem.
317		688
318	Per-thread usage:	689	Per-thread usage:
319		690
320	In the execution phase, some aio requests require more memory for	691	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	692	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	693	structures (usually around 16k-128k, depending on the OS).
323		694
324	=head1 KNOWN BUGS	695	=head1 KNOWN BUGS
325		696
326	Known bugs will be fixed in the next release.	697	Known bugs will be fixed in the next release, except:
		698
		699	If you use a transaction in any request, and the request returns
		700	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		701	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		702	above.
327		703
328	=head1 SEE ALSO	704	=head1 SEE ALSO
329		705
330	L<Coro::AIO>.	706	L<Coro::BDB>, L<IO::AIO>.
331		707
332	=head1 AUTHOR	708	=head1 AUTHOR
333		709
334	Marc Lehmann <schmorp@schmorp.de>	710	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	711	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 1.25 by root, Mon Dec 10 21:19:06 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 1.25 by root, Mon Dec 10 21:19:06 2007 UTC