[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 1.38 by root, Mon Jul 7 22:11:04 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	BDB::AIO - Asynchronous Berkeley DB access	3	BDB - Asynchronous Berkeley DB access
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB::AIO;	7	use BDB;
		8
		9	my $env = db_env_create;
		10
		11	mkdir "bdtest", 0700;
		12	db_env_open
		13	$env,
		14	"bdtest",
		15	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL
		16	\| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		17	0600;
		18
		19	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		20
		21	my $db = db_create $env;
		22	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE
		23	\| BDB::READ_UNCOMMITTED, 0600;
		24	db_put $db, undef, "key", "data", 0, sub {
		25	db_del $db, undef, "key";
		26	};
		27	db_sync $db;
		28
		29	# when you also use Coro, management is easy:
		30	use Coro::BDB;
		31
		32	# automatic event loop intergration with AnyEvent:
		33	use AnyEvent::BDB;
		34
		35	# automatic result processing with EV:
		36	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		37
		38	# with Glib:
		39	add_watch Glib::IO BDB::poll_fileno,
		40	in => sub { BDB::poll_cb; 1 };
		41
		42	# or simply flush manually
		43	BDB::flush;
		44
8		45
9	=head1 DESCRIPTION	46	=head1 DESCRIPTION
10		47
11	=head2 EXAMPLE	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		49	The BDB API is very similar to the C API (the translation has been very faithful).
		50
		51	See also the example sections in the document below and possibly the eg/
		52	subdirectory of the BDB distribution. Last not least see the IO::AIO
		53	documentation, as that module uses almost the same asynchronous request
		54	model as this module.
		55
		56	I know this is woefully inadequate documentation. Send a patch!
		57
12		58
13	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
14		60
15	Every request method creates a request. which is a C data structure not	61	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	62	directly visible to Perl.
55		101
56	=back	102	=back
57		103
58	=cut	104	=cut
59		105
60	package BDB::AIO;	106	package BDB;
61		107
62	no warnings;	108	no warnings;
63	use strict 'vars';	109	use strict 'vars';
64		110
65	use base 'Exporter';	111	use base 'Exporter';
66		112
67	BEGIN {	113	BEGIN {
68	our $VERSION = '0.1';	114	our $VERSION = '1.5';
69		115
70	our @BDB_REQ = qw();	116	our @BDB_REQ = qw(
		117	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		118	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
		119	db_open db_close db_compact db_sync db_upgrade
		120	db_put db_get db_pget db_del db_key_range
		121	db_txn_commit db_txn_abort db_txn_finish
		122	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		123	db_sequence_open db_sequence_close
		124	db_sequence_get db_sequence_remove
		125	);
		126	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		127	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	128	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	129	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	130	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	131	max_poll_time max_poll_reqs
		132	);
75		133
76	require XSLoader;	134	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	135	XSLoader::load ("BDB", $VERSION);
78	}	136	}
79		137
		138	=head2 WIN32 FILENAMES/DATABASE NAME MESS
		139
		140	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		141	an internal flag to store wether a filename is Unicode or ANSI, but that
		142	flag is used for somethign else in the perl core, so there is no way to
		143	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		144	tries to work around this issue by assuming that the filename is an ANSI
		145	filename and BDB was built for unicode support.
		146
		147	=head2 BERKELEYDB FUNCTIONS
		148
		149	All of these are functions. The create functions simply return a new
		150	object and never block. All the remaining functions take an optional
		151	callback as last argument. If it is missing, then the function will be
		152	executed synchronously. In both cases, C<$!> will reflect the return value
		153	of the function.
		154
		155	BDB functions that cannot block (mostly functions that manipulate
		156	settings) are method calls on the relevant objects, so the rule of thumb
		157	is: if it's a method, it's not blocking, if it's a function, it takes a
		158	callback as last argument.
		159
		160	In the following, C<$int> signifies an integer return value,
		161	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		162	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		163	floating point value.
		164
		165	The C<SV *> types are generic perl scalars (for input and output of data
		166	values), and the C<SV *callback> is the optional callback function to call
		167	when the request is completed.
		168
		169	The various C<DB_ENV> etc. arguments are handles return by
		170	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		171	appended C<_ornull> this means they are optional and you can pass C<undef>
		172	for them, resulting a NULL pointer on the C level.
		173
		174	=head3 BDB functions
		175
		176	Functions in the BDB namespace, exported by default:
		177
		178	$env = db_env_create (U32 env_flags = 0)
		179	flags: RPCCLIENT
		180
		181	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		182	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
		183	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		184	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		185	flags: FORCE
		186	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		187	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		188	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		189	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		190	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		191	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef)
		192
		193	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		194	flags: XA_CREATE
		195
		196	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		197	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		198	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		199	flags: DB_NOSYNC
		200	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		201	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)
		202	flags: FREELIST_ONLY FREE_SPACE
		203	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		204	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		205	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		206	flags: APPEND NODUPDATA NOOVERWRITE
		207	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		209	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		210	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		211	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		212	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		213	flags: TXN_NOSYNC TXN_SYNC
		214	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		215
		216	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		217	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		218	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		219	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		220	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		221	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
		222	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		223	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		224
		225	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		226	flags: CREATE EXCL
		227	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		228	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)
		229	flags: TXN_NOSYNC
		230	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		231	flags: TXN_NOSYNC
		232
		233	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		234
		235	This is not actually a Berkeley DB function but a BDB module
		236	extension. The background for this exytension is: It is very annoying to
		237	have to check every single BDB function for error returns and provide a
		238	codepath out of your transaction. While the BDB module still makes this
		239	possible, it contains the following extensions:
		240
		241	When a transaction-protected function returns any operating system
		242	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		243	transaction. This flag is also set by Berkeley DB functions themselves
		244	when an operation fails with LOCK_DEADLOCK, and it causes all further
		245	operations on that transaction (including C<db_txn_commit>) to fail.
		246
		247	The C<db_txn_finish> request will look at this flag, and, if it is set,
		248	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		249	if it isn't set to something else yet). If it isn't set, it will call
		250	C<db_txn_commit> and return the error normally.
		251
		252	How to use this? Easy: just write your transaction normally:
		253
		254	my $txn = $db_env->txn_begin;
		255	db_get $db, $txn, "key", my $data;
		256	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		257	db_txn_finish $txn;
		258	die "transaction failed" if $!;
		259
		260	That is, handle only the expected errors. If something unexpected happens
		261	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		262	requests (db_put in this case) will simply be skipped (they will fail with
		263	LOCK_DEADLOCK) and the transaction will be aborted.
		264
		265	You can use the C<< $txn->failed >> method to check wether a transaction
		266	has failed in this way and abort further processing (excluding
		267	C<db_txn_finish>).
		268
		269	=head3 DB_ENV/database environment methods
		270
		271	Methods available on DB_ENV/$env handles:
		272
		273	DESTROY (DB_ENV_ornull *env)
		274	CODE:
		275	if (env)
		276	env->close (env, 0);
		277
		278	$int = $env->set_data_dir (const char *dir)
		279	$int = $env->set_tmp_dir (const char *dir)
		280	$int = $env->set_lg_dir (const char *dir)
		281	$int = $env->set_shm_key (long shm_key)
		282	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		283	$int = $env->set_flags (U32 flags, int onoff)
		284	$env->set_errfile (FILE *errfile = 0)
		285	$env->set_msgfile (FILE *msgfile = 0)
		286	$int = $env->set_verbose (U32 which, int onoff = 1)
		287	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		288	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		289	$int = $env->set_mp_max_openfd (int maxopenfd);
		290	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		291	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		292	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		293	$int = $env->set_lk_max_lockers (U32 max)
		294	$int = $env->set_lk_max_locks (U32 max)
		295	$int = $env->set_lk_max_objects (U32 max)
		296	$int = $env->set_lg_bsize (U32 max)
		297	$int = $env->set_lg_max (U32 max)
		298	$int = $env->mutex_set_increment (U32 increment)
		299	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		300	$int = $env->mutex_set_max (U32 max)
		301	$int = $env->mutex_set_align (U32 align)
		302
		303	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		304	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		305
		306	=head4 Example:
		307
		308	use AnyEvent;
		309	use BDB;
		310
		311	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		312	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		313
		314	BDB::min_parallel 8;
		315
		316	my $env = db_env_create;
		317
		318	mkdir "bdtest", 0700;
		319	db_env_open
		320	$env,
		321	"bdtest",
		322	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		323	0600;
		324
		325	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		326
		327
		328	=head3 DB/database methods
		329
		330	Methods available on DB/$db handles:
		331
		332	DESTROY (DB_ornull *db)
		333	CODE:
		334	if (db)
		335	{
		336	SV env = (SV )db->app_private;
		337	db->close (db, 0);
		338	SvREFCNT_dec (env);
		339	}
		340
		341	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		342	$int = $db->set_flags (U32 flags)
		343	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		344	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		345	Hash: DUP DUPSORT
		346	Queue: INORDER
		347	Recno: RENUMBER SNAPSHOT
		348
		349	$int = $db->set_encrypt (const char *password, U32 flags)
		350	$int = $db->set_lorder (int lorder)
		351	$int = $db->set_bt_minkey (U32 minkey)
		352	$int = $db->set_re_delim (int delim)
		353	$int = $db->set_re_pad (int re_pad)
		354	$int = $db->set_re_source (char *source)
		355	$int = $db->set_re_len (U32 re_len)
		356	$int = $db->set_h_ffactor (U32 h_ffactor)
		357	$int = $db->set_h_nelem (U32 h_nelem)
		358	$int = $db->set_q_extentsize (U32 extentsize)
		359
		360	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		361	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		362	$seq = $db->sequence (U32 flags = 0)
		363
		364	=head4 Example:
		365
		366	my $db = db_create $env;
		367	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		368
		369	for (1..1000) {
		370	db_put $db, undef, "key $_", "data $_";
		371
		372	db_key_range $db, undef, "key $_", my $keyrange;
		373	my ($lt, $eq, $gt) = @$keyrange;
		374	}
		375
		376	db_del $db, undef, "key $_" for 1..1000;
		377
		378	db_sync $db;
		379
		380
		381	=head3 DB_TXN/transaction methods
		382
		383	Methods available on DB_TXN/$txn handles:
		384
		385	DESTROY (DB_TXN_ornull *txn)
		386	CODE:
		387	if (txn)
		388	txn->abort (txn);
		389
		390	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		391	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		392
		393	$bool = $txn->failed
		394	# see db_txn_finish documentation, above
		395
		396
		397	=head3 DBC/cursor methods
		398
		399	Methods available on DBC/$dbc handles:
		400
		401	DESTROY (DBC_ornull *dbc)
		402	CODE:
		403	if (dbc)
		404	dbc->c_close (dbc);
		405
		406	$int = $cursor->set_priority ($priority = PRIORITY_*)
		407
		408	=head4 Example:
		409
		410	my $c = $db->cursor;
		411
		412	for (;;) {
		413	db_c_get $c, my $key, my $data, BDB::NEXT;
		414	warn "<$!,$key,$data>";
		415	last if $!;
		416	}
		417
		418	db_c_close $c;
		419
		420
		421	=head3 DB_SEQUENCE/sequence methods
		422
		423	Methods available on DB_SEQUENCE/$seq handles:
		424
		425	DESTROY (DB_SEQUENCE_ornull *seq)
		426	CODE:
		427	if (seq)
		428	seq->close (seq, 0);
		429
		430	$int = $seq->initial_value (db_seq_t value)
		431	$int = $seq->set_cachesize (U32 size)
		432	$int = $seq->set_flags (U32 flags)
		433	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		434	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		435
		436	=head4 Example:
		437
		438	my $seq = $db->sequence;
		439
		440	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		441	db_sequence_get $seq, undef, 1, my $value;
		442
		443
80	=head2 SUPPORT FUNCTIONS	444	=head2 SUPPORT FUNCTIONS
81		445
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	446	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		447
84	=over 4	448	=over 4
85		449
		450	=item $msg = BDB::strerror [$errno]
		451
		452	Returns the string corresponding to the given errno value. If no argument
		453	is given, use C<$!>.
		454
		455	Note that the BDB module also patches the C<$!> variable directly, so you
		456	should be able to get a bdb error string by simply stringifying C<$!>.
		457
86	=item $fileno = BDB::AIO::poll_fileno	458	=item $fileno = BDB::poll_fileno
87		459
88	Return the I<request result pipe file descriptor>. This filehandle must be	460	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	461	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	462	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	463	to call C<poll_cb> to check the results.
92		464
93	See C<poll_cb> for an example.	465	See C<poll_cb> for an example.
94		466
95	=item BDB::AIO::poll_cb	467	=item BDB::poll_cb
96		468
97	Process some outstanding events on the result pipe. You have to call this	469	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	470	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	471	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>.	472	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		473
102	If not all requests were processed for whatever reason, the filehandle	474	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	475	will still be ready when C<poll_cb> returns.
104		476
105	Example: Install an Event watcher that automatically calls	477	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	478	BDB::poll_cb with high priority:
107		479
108	Event->io (fd => BDB::AIO::poll_fileno,	480	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	481	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	482	cb => \&BDB::poll_cb);
111		483
112	=item BDB::AIO::max_poll_reqs $nreqs	484	=item BDB::max_poll_reqs $nreqs
113		485
114	=item BDB::AIO::max_poll_time $seconds	486	=item BDB::max_poll_time $seconds
115		487
116	These set the maximum number of requests (default C<0>, meaning infinity)	488	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	489	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	490	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	491	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	492	of time C<poll_cb> is allowed to use).
121		493
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	494	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	495	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	496	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	500	interactiveness when perl is not fast enough to process all requests in
129	time.	501	time.
130		502
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	503	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		504
133	Example: Install an Event watcher that automatically calls	505	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	506	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	507	program get the CPU sometimes even under high load.
136		508
137	# try not to spend much more than 0.1s in poll_cb	509	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	510	BDB::max_poll_time 0.1;
139		511
140	# use a low priority so other tasks have priority	512	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		513
145	=item BDB::AIO::poll_wait	514	=item BDB::poll_wait
146		515
147	If there are any outstanding requests and none of them in the result	516	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	517	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	518	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	519	synchronously wait for some requests to finish).
151		520
152	See C<nreqs> for an example.	521	See C<nreqs> for an example.
153		522
154	=item BDB::AIO::poll	523	=item BDB::poll
155		524
156	Waits until some requests have been handled.	525	Waits until some requests have been handled.
157		526
158	Returns the number of requests processed, but is otherwise strictly	527	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	528	equivalent to:
160		529
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	530	BDB::poll_wait, BDB::poll_cb
162		531
163	=item BDB::AIO::flush	532	=item BDB::flush
164		533
165	Wait till all outstanding AIO requests have been handled.	534	Wait till all outstanding BDB requests have been handled.
166		535
167	Strictly equivalent to:	536	Strictly equivalent to:
168		537
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	538	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	539	while BDB::nreqs;
		540
		541	=back
171		542
172	=head3 CONTROLLING THE NUMBER OF THREADS	543	=head3 CONTROLLING THE NUMBER OF THREADS
173		544
		545	=over 4
		546
174	=item BDB::AIO::min_parallel $nthreads	547	=item BDB::min_parallel $nthreads
175		548
176	Set the minimum number of AIO threads to C<$nthreads>. The current	549	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	550	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	551	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	552	however, is unlimited).
180		553
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	554	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	555	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	556	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.	557	is in the cache and could have been processed faster by a single thread.
185		558
186	It is recommended to keep the number of threads relatively low, as some	559	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	562	versions, 4-32 threads should be fine.
190		563
191	Under most circumstances you don't need to call this function, as the	564	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.	565	module selects a default that is suitable for low to moderate load.
193		566
194	=item BDB::AIO::max_parallel $nthreads	567	=item BDB::max_parallel $nthreads
195		568
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	569	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	570	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	571	them. This function blocks until the limit is reached.
199		572
200	While C<$nthreads> are zero, aio requests get queued but not executed	573	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	574	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	576	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.	577	that all threads are killed and that there are no outstanding requests.
205		578
206	Under normal circumstances you don't need to call this function.	579	Under normal circumstances you don't need to call this function.
207		580
208	=item BDB::AIO::max_idle $nthreads	581	=item BDB::max_idle $nthreads
209		582
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	583	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	584	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	585	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	586	idle, it will free its resources and exit.
…		…
218		591
219	The default is probably ok in most situations, especially if thread	592	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	593	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	594	want to use larger values.
222		595
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	596	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		597
225	This is a very bad function to use in interactive programs because it	598	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	599	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	600	use an C<aio_group> together with a feed callback.
228		601
…		…
236		609
237	You can still queue as many requests as you want. Therefore,	610	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	611	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).	612	as a stop gap to shield against fatal memory overflow (with large values).
240		613
		614	=item BDB::set_sync_prepare $cb
		615
		616	Sets a callback that is called whenever a request is created without an
		617	explicit callback. It has to return two code references. The first is used
		618	as the request callback (it should save the return status), and the second
		619	is called to wait until the first callback has been called (it must set
		620	C<$!> to the return status).
		621
		622	This mechanism can be used to include BDB into other event mechanisms,
		623	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		624
		625	The default implementation works like this:
		626
		627	sub {
		628	my $status;
		629	(
		630	sub { $status = $! },
		631	sub { BDB::poll while !defined $status; $! = $status },
		632	)
		633	}
		634
		635	It simply blocks the process till the request has finished and then sets
		636	C<$!> to the return value. This means that if you don't use a callback,
		637	BDB will simply fall back to synchronous operations.
		638
		639	=back
		640
241	=head3 STATISTICAL INFORMATION	641	=head3 STATISTICAL INFORMATION
242		642
		643	=over 4
		644
243	=item BDB::AIO::nreqs	645	=item BDB::nreqs
244		646
245	Returns the number of requests currently in the ready, execute or pending	647	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).	648	states (i.e. for which their callback has not been invoked yet).
247		649
248	Example: wait till there are no outstanding requests anymore:	650	Example: wait till there are no outstanding requests anymore:
249		651
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	652	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	653	while BDB::nreqs;
252		654
253	=item BDB::AIO::nready	655	=item BDB::nready
254		656
255	Returns the number of requests currently in the ready state (not yet	657	Returns the number of requests currently in the ready state (not yet
256	executed).	658	executed).
257		659
258	=item BDB::AIO::npending	660	=item BDB::npending
259		661
260	Returns the number of requests currently in the pending state (executed,	662	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	663	but not yet processed by poll_cb).
262		664
263	=back	665	=back
264		666
265	=cut	667	=cut
266		668
267	# support function to convert a fd into a perl filehandle	669	set_sync_prepare {
268	sub _fd2fh {	670	my $status;
269	return undef if $_[0] < 0;	671	(
270		672	sub {
271	# try to generate nice filehandles	673	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	674	},
273	local *$sym;	675	sub {
274		676	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	677	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	678	},
277	or open *$sym, ">&=$_[0]" # or this	679	)
278	or return undef;	680	};
279
280	*$sym
281	}
282		681
283	min_parallel 8;	682	min_parallel 8;
284		683
285	END { flush }	684	END { flush }
286		685
…		…
288		687
289	=head2 FORK BEHAVIOUR	688	=head2 FORK BEHAVIOUR
290		689
291	This module should do "the right thing" when the process using it forks:	690	This module should do "the right thing" when the process using it forks:
292		691
293	Before the fork, IO::AIO enters a quiescent state where no requests	692	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	693	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	694	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	695	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	696	(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	697	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	698	parent process has been reached again.
300		699
301	In short: the parent will, after a short pause, continue as if fork had	700	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	701	not been called, while the child will act as if BDB has not been used
303	yet.	702	yet.
		703
		704	Win32 note: there is no fork on win32, and perls emulation of it is too
		705	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		706	yet, switch to a more capable platform.
304		707
305	=head2 MEMORY USAGE	708	=head2 MEMORY USAGE
306		709
307	Per-request usage:	710	Per-request usage:
308		711
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	713	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	714	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	715	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.	716	will consume memory till the request has entered the done state.
314		717
315	This is now awfully much, so queuing lots of requests is not usually a	718	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	719	problem.
317		720
318	Per-thread usage:	721	Per-thread usage:
319		722
320	In the execution phase, some aio requests require more memory for	723	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	724	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	725	structures (usually around 16k-128k, depending on the OS).
323		726
324	=head1 KNOWN BUGS	727	=head1 KNOWN BUGS
325		728
326	Known bugs will be fixed in the next release.	729	Known bugs will be fixed in the next release, except:
		730
		731	If you use a transaction in any request, and the request returns
		732	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		733	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		734	above.
327		735
328	=head1 SEE ALSO	736	=head1 SEE ALSO
329		737
330	L<Coro::AIO>.	738	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		739	syntax), L<IO::AIO> (nice to have).
331		740
332	=head1 AUTHOR	741	=head1 AUTHOR
333		742
334	Marc Lehmann <schmorp@schmorp.de>	743	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	744	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 1.38 by root, Mon Jul 7 22:11:04 2008 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 1.38 by root, Mon Jul 7 22:11:04 2008 UTC