[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 1.22 by root, Mon Dec 10 03:57:27 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_put db_get db_pget db_del db_key_range
		118	db_txn_commit db_txn_abort db_txn_finish
		119	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		120	db_sequence_open db_sequence_close
		121	db_sequence_get db_sequence_remove
		122	);
		123	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		124	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	125	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	126	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	127	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	128	max_poll_time max_poll_reqs
		129	);
75		130
76	require XSLoader;	131	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	132	XSLoader::load ("BDB", $VERSION);
78	}	133	}
79		134
		135	=head2 BERKELEYDB FUNCTIONS
		136
		137	All of these are functions. The create functions simply return a new
		138	object and never block. All the remaining functions all take an optional
		139	callback as last argument that gets passed the return value. If it is
		140	missing, then the function will be executed synchronously, and the return
		141	value is returned as normally.
		142
		143	BDB functions that cannot block (mostly functions that manipulate
		144	settings) are method calls on the relevant objects, so the rule of thumb
		145	is: if its a method, its not blocking, if its a function, it takes a
		146	callback as last argument.
		147
		148	In the following, C<$int> signifies an integer return value,
		149	C<octetstring> is a "binary string" (i.e. a perl string with no character
		150	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		151	integer, C<NV> is a floating point value.
		152
		153	The C<SV *> types are generic perl scalars (for input and output of data
		154	values), and the C<SV *callback> is the optional callback function to call
		155	when the request is completed.
		156
		157	The various C<DB_ENV> etc. arguments are handles return by
		158	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		159	appended C<_ornull> this means they are optional and you can pass C<undef>
		160	for them, resulting a NULL pointer on the C level.
		161
		162	=head3 BDB functions
		163
		164	Functions in the BDB namespace, exported by default:
		165
		166	$env = db_env_create (U32 env_flags = 0)
		167	flags: RPCCLIENT
		168
		169	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		170	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
		171	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		172	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		173	flags: FORCE
		174	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		175	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		176	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		177	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		178
		179	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		180	flags: XA_CREATE
		181
		182	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		183	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		184	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		185	flags: DB_NOSYNC
		186	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)
		187	flags: FREELIST_ONLY FREE_SPACE
		188	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		189	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		190	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		191	flags: APPEND NODUPDATA NOOVERWRITE
		192	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		193	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		194	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, 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_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		197	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		198	flags: TXN_NOSYNC TXN_SYNC
		199	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		200
		201	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		202	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		203	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		204	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		205	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		206	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
		207	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		209
		210	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		211	flags: CREATE EXCL
		212	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		213	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)
		214	flags: TXN_NOSYNC
		215	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		216	flags: TXN_NOSYNC
		217
		218	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		219
		220	This is not actually a Berkeley DB function but a BDB module
		221	extension. The background for this exytension is: It is very annoying to
		222	have to check every single BDB function for error returns and provide a
		223	codepath out of your transaction. While the BDB module still makes this
		224	possible, it contains the following extensions:
		225
		226	When a transaction-protected function returns any operating system
		227	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		228	transaction. This flag is also set by Berkeley DB functions themselves
		229	when an operation fails with LOCK_DEADLOCK, and it causes all further
		230	operations on that transaction (including C<db_txn_commit>) to fail.
		231
		232	The C<db_txn_finish> request will look at this flag, and, if it is set,
		233	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		234	if it isn't set to something else yet). If it isn't set, it will call
		235	C<db_txn_commit> and return the error normally.
		236
		237	How to use this? Easy: just write your transaction normally:
		238
		239	my $txn = $db_env->txn_begin;
		240	db_get $db, $txn, "key", my $data;
		241	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		242	db_txn_finish $txn;
		243	die "transaction failed" if $!;
		244
		245	That is, handle only the expected errors. If something unexpected happens
		246	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		247	requests (db_put in this case) will simply be skipped (they will fail with
		248	LOCK_DEADLOCK) and the transaction will be aborted.
		249
		250	You can use the C<< $txn->failed >> method to check wether a transaction
		251	has failed in this way and abort further processing (excluding
		252	C<db_txn_finish>).
		253
		254	=head3 DB_ENV/database environment methods
		255
		256	Methods available on DB_ENV/$env handles:
		257
		258	DESTROY (DB_ENV_ornull *env)
		259	CODE:
		260	if (env)
		261	env->close (env, 0);
		262
		263	$int = $env->set_data_dir (const char *dir)
		264	$int = $env->set_tmp_dir (const char *dir)
		265	$int = $env->set_lg_dir (const char *dir)
		266	$int = $env->set_shm_key (long shm_key)
		267	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		268	$int = $env->set_flags (U32 flags, int onoff)
		269	$env->set_errfile (FILE *errfile = 0)
		270	$env->set_msgfile (FILE *msgfile = 0)
		271	$int = $env->set_verbose (U32 which, int onoff = 1)
		272	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		273	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		274	$int = $env->set_mp_max_openfd (int maxopenfd);
		275	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		276	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		277	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		278	$int = $env->set_lk_max_lockers (U32 max)
		279	$int = $env->set_lk_max_locks (U32 max)
		280	$int = $env->set_lk_max_objects (U32 max)
		281	$int = $env->set_lg_bsize (U32 max)
		282	$int = $env->set_lg_max (U32 max)
		283	$int = $env->mutex_set_increment (U32 increment)
		284	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		285	$int = $env->mutex_set_max (U32 max)
		286	$int = $env->mutex_set_align (U32 align)
		287
		288	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		289	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		290
		291	=head4 Example:
		292
		293	use AnyEvent;
		294	use BDB;
		295
		296	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		297	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		298
		299	BDB::min_parallel 8;
		300
		301	my $env = db_env_create;
		302
		303	mkdir "bdtest", 0700;
		304	db_env_open
		305	$env,
		306	"bdtest",
		307	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		308	0600;
		309
		310	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		311
		312
		313	=head3 DB/database methods
		314
		315	Methods available on DB/$db handles:
		316
		317	DESTROY (DB_ornull *db)
		318	CODE:
		319	if (db)
		320	{
		321	SV env = (SV )db->app_private;
		322	db->close (db, 0);
		323	SvREFCNT_dec (env);
		324	}
		325
		326	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		327	$int = $db->set_flags (U32 flags)
		328	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		329	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		330	Hash: DUP DUPSORT
		331	Queue: INORDER
		332	Recno: RENUMBER SNAPSHOT
		333
		334	$int = $db->set_encrypt (const char *password, U32 flags)
		335	$int = $db->set_lorder (int lorder)
		336	$int = $db->set_bt_minkey (U32 minkey)
		337	$int = $db->set_re_delim (int delim)
		338	$int = $db->set_re_pad (int re_pad)
		339	$int = $db->set_re_source (char *source)
		340	$int = $db->set_re_len (U32 re_len)
		341	$int = $db->set_h_ffactor (U32 h_ffactor)
		342	$int = $db->set_h_nelem (U32 h_nelem)
		343	$int = $db->set_q_extentsize (U32 extentsize)
		344
		345	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		346	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		347	$seq = $db->sequence (U32 flags = 0)
		348
		349	=head4 Example:
		350
		351	my $db = db_create $env;
		352	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		353
		354	for (1..1000) {
		355	db_put $db, undef, "key $_", "data $_";
		356
		357	db_key_range $db, undef, "key $_", my $keyrange;
		358	my ($lt, $eq, $gt) = @$keyrange;
		359	}
		360
		361	db_del $db, undef, "key $_" for 1..1000;
		362
		363	db_sync $db;
		364
		365
		366	=head3 DB_TXN/transaction methods
		367
		368	Methods available on DB_TXN/$txn handles:
		369
		370	DESTROY (DB_TXN_ornull *txn)
		371	CODE:
		372	if (txn)
		373	txn->abort (txn);
		374
		375	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		376	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		377
		378	$bool = $txn->failed
		379	# see db_txn_finish documentation, above
		380
		381
		382	=head3 DBC/cursor methods
		383
		384	Methods available on DBC/$dbc handles:
		385
		386	DESTROY (DBC_ornull *dbc)
		387	CODE:
		388	if (dbc)
		389	dbc->c_close (dbc);
		390
		391	=head4 Example:
		392
		393	my $c = $db->cursor;
		394
		395	for (;;) {
		396	db_c_get $c, my $key, my $data, BDB::NEXT;
		397	warn "<$!,$key,$data>";
		398	last if $!;
		399	}
		400
		401	db_c_close $c;
		402
		403
		404	=head3 DB_SEQUENCE/sequence methods
		405
		406	Methods available on DB_SEQUENCE/$seq handles:
		407
		408	DESTROY (DB_SEQUENCE_ornull *seq)
		409	CODE:
		410	if (seq)
		411	seq->close (seq, 0);
		412
		413	$int = $seq->initial_value (db_seq_t value)
		414	$int = $seq->set_cachesize (U32 size)
		415	$int = $seq->set_flags (U32 flags)
		416	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		417	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		418
		419	=head4 Example:
		420
		421	my $seq = $db->sequence;
		422
		423	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		424	db_sequence_get $seq, undef, 1, my $value;
		425
		426
80	=head2 SUPPORT FUNCTIONS	427	=head2 SUPPORT FUNCTIONS
81		428
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	429	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		430
84	=over 4	431	=over 4
85		432
86	=item $fileno = BDB::AIO::poll_fileno	433	=item $fileno = BDB::poll_fileno
87		434
88	Return the I<request result pipe file descriptor>. This filehandle must be	435	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	436	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	437	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	438	to call C<poll_cb> to check the results.
92		439
93	See C<poll_cb> for an example.	440	See C<poll_cb> for an example.
94		441
95	=item BDB::AIO::poll_cb	442	=item BDB::poll_cb
96		443
97	Process some outstanding events on the result pipe. You have to call this	444	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	445	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	446	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>.	447	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		448
102	If not all requests were processed for whatever reason, the filehandle	449	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	450	will still be ready when C<poll_cb> returns.
104		451
105	Example: Install an Event watcher that automatically calls	452	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	453	BDB::poll_cb with high priority:
107		454
108	Event->io (fd => BDB::AIO::poll_fileno,	455	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	456	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	457	cb => \&BDB::poll_cb);
111		458
112	=item BDB::AIO::max_poll_reqs $nreqs	459	=item BDB::max_poll_reqs $nreqs
113		460
114	=item BDB::AIO::max_poll_time $seconds	461	=item BDB::max_poll_time $seconds
115		462
116	These set the maximum number of requests (default C<0>, meaning infinity)	463	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	464	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	465	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	466	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	467	of time C<poll_cb> is allowed to use).
121		468
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	469	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	470	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	471	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	475	interactiveness when perl is not fast enough to process all requests in
129	time.	476	time.
130		477
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	478	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		479
133	Example: Install an Event watcher that automatically calls	480	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	481	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	482	program get the CPU sometimes even under high load.
136		483
137	# try not to spend much more than 0.1s in poll_cb	484	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	485	BDB::max_poll_time 0.1;
139		486
140	# use a low priority so other tasks have priority	487	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		488
145	=item BDB::AIO::poll_wait	489	=item BDB::poll_wait
146		490
147	If there are any outstanding requests and none of them in the result	491	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	492	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	493	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	494	synchronously wait for some requests to finish).
151		495
152	See C<nreqs> for an example.	496	See C<nreqs> for an example.
153		497
154	=item BDB::AIO::poll	498	=item BDB::poll
155		499
156	Waits until some requests have been handled.	500	Waits until some requests have been handled.
157		501
158	Returns the number of requests processed, but is otherwise strictly	502	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	503	equivalent to:
160		504
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	505	BDB::poll_wait, BDB::poll_cb
162		506
163	=item BDB::AIO::flush	507	=item BDB::flush
164		508
165	Wait till all outstanding AIO requests have been handled.	509	Wait till all outstanding BDB requests have been handled.
166		510
167	Strictly equivalent to:	511	Strictly equivalent to:
168		512
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	513	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	514	while BDB::nreqs;
		515
		516	=back
171		517
172	=head3 CONTROLLING THE NUMBER OF THREADS	518	=head3 CONTROLLING THE NUMBER OF THREADS
173		519
		520	=over 4
		521
174	=item BDB::AIO::min_parallel $nthreads	522	=item BDB::min_parallel $nthreads
175		523
176	Set the minimum number of AIO threads to C<$nthreads>. The current	524	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	525	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	526	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	527	however, is unlimited).
180		528
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	529	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	530	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	531	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.	532	is in the cache and could have been processed faster by a single thread.
185		533
186	It is recommended to keep the number of threads relatively low, as some	534	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	537	versions, 4-32 threads should be fine.
190		538
191	Under most circumstances you don't need to call this function, as the	539	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.	540	module selects a default that is suitable for low to moderate load.
193		541
194	=item BDB::AIO::max_parallel $nthreads	542	=item BDB::max_parallel $nthreads
195		543
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	544	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	545	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	546	them. This function blocks until the limit is reached.
199		547
200	While C<$nthreads> are zero, aio requests get queued but not executed	548	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	549	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	551	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.	552	that all threads are killed and that there are no outstanding requests.
205		553
206	Under normal circumstances you don't need to call this function.	554	Under normal circumstances you don't need to call this function.
207		555
208	=item BDB::AIO::max_idle $nthreads	556	=item BDB::max_idle $nthreads
209		557
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	558	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	559	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	560	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	561	idle, it will free its resources and exit.
…		…
218		566
219	The default is probably ok in most situations, especially if thread	567	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	568	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	569	want to use larger values.
222		570
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	571	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		572
225	This is a very bad function to use in interactive programs because it	573	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	574	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	575	use an C<aio_group> together with a feed callback.
228		576
…		…
236		584
237	You can still queue as many requests as you want. Therefore,	585	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	586	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).	587	as a stop gap to shield against fatal memory overflow (with large values).
240		588
		589	=item BDB::set_sync_prepare $cb
		590
		591	Sets a callback that is called whenever a request is created without an
		592	explicit callback. It has to return two code references. The first is used
		593	as the request callback, and the second is called to wait until the first
		594	callback has been called. The default implementation works like this:
		595
		596	sub {
		597	my $status;
		598	(
		599	sub { $status = $! },
		600	sub { BDB::poll while !defined $status; $! = $status },
		601	)
		602	}
		603
		604	=back
		605
241	=head3 STATISTICAL INFORMATION	606	=head3 STATISTICAL INFORMATION
242		607
		608	=over 4
		609
243	=item BDB::AIO::nreqs	610	=item BDB::nreqs
244		611
245	Returns the number of requests currently in the ready, execute or pending	612	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).	613	states (i.e. for which their callback has not been invoked yet).
247		614
248	Example: wait till there are no outstanding requests anymore:	615	Example: wait till there are no outstanding requests anymore:
249		616
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	617	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	618	while BDB::nreqs;
252		619
253	=item BDB::AIO::nready	620	=item BDB::nready
254		621
255	Returns the number of requests currently in the ready state (not yet	622	Returns the number of requests currently in the ready state (not yet
256	executed).	623	executed).
257		624
258	=item BDB::AIO::npending	625	=item BDB::npending
259		626
260	Returns the number of requests currently in the pending state (executed,	627	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	628	but not yet processed by poll_cb).
262		629
263	=back	630	=back
264		631
265	=cut	632	=cut
266		633
267	# support function to convert a fd into a perl filehandle	634	set_sync_prepare {
268	sub _fd2fh {	635	my $status;
269	return undef if $_[0] < 0;	636	(
270		637	sub {
271	# try to generate nice filehandles	638	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	639	},
273	local *$sym;	640	sub {
274		641	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	642	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	643	},
277	or open *$sym, ">&=$_[0]" # or this	644	)
278	or return undef;	645	};
279
280	*$sym
281	}
282		646
283	min_parallel 8;	647	min_parallel 8;
284		648
285	END { flush }	649	END { flush }
286		650
…		…
288		652
289	=head2 FORK BEHAVIOUR	653	=head2 FORK BEHAVIOUR
290		654
291	This module should do "the right thing" when the process using it forks:	655	This module should do "the right thing" when the process using it forks:
292		656
293	Before the fork, IO::AIO enters a quiescent state where no requests	657	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	658	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	659	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	660	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	661	(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	662	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	663	parent process has been reached again.
300		664
301	In short: the parent will, after a short pause, continue as if fork had	665	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	666	not been called, while the child will act as if BDB has not been used
303	yet.	667	yet.
304		668
305	=head2 MEMORY USAGE	669	=head2 MEMORY USAGE
306		670
307	Per-request usage:	671	Per-request usage:
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	674	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	675	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	676	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.	677	will consume memory till the request has entered the done state.
314		678
315	This is now awfully much, so queuing lots of requests is not usually a	679	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	680	problem.
317		681
318	Per-thread usage:	682	Per-thread usage:
319		683
320	In the execution phase, some aio requests require more memory for	684	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	685	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	686	structures (usually around 16k-128k, depending on the OS).
323		687
324	=head1 KNOWN BUGS	688	=head1 KNOWN BUGS
325		689
326	Known bugs will be fixed in the next release.	690	Known bugs will be fixed in the next release, except:
		691
		692	If you use a transaction in any request, and the request returns
		693	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		694	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		695	above.
327		696
328	=head1 SEE ALSO	697	=head1 SEE ALSO
329		698
330	L<Coro::AIO>.	699	L<Coro::BDB>, L<IO::AIO>.
331		700
332	=head1 AUTHOR	701	=head1 AUTHOR
333		702
334	Marc Lehmann <schmorp@schmorp.de>	703	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	704	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 1.22 by root, Mon Dec 10 03:57:27 2007 UTC

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Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.22 by root, Mon Dec 10 03:57:27 2007 UTC