[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 1.40 by root, Tue Jul 8 08:35:12 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 = '1.6';
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 = 1)
		284	$int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
		285	$int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
		286	$env->set_errfile (FILE *errfile = 0)
		287	$env->set_msgfile (FILE *msgfile = 0)
		288	$int = $env->set_verbose (U32 which, int onoff = 1)
		289	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		290	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		291	$int = $env->set_mp_max_openfd (int maxopenfd);
		292	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		293	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		294	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		295	$int = $env->set_lk_max_lockers (U32 max)
		296	$int = $env->set_lk_max_locks (U32 max)
		297	$int = $env->set_lk_max_objects (U32 max)
		298	$int = $env->set_lg_bsize (U32 max)
		299	$int = $env->set_lg_max (U32 max)
		300	$int = $env->mutex_set_increment (U32 increment)
		301	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		302	$int = $env->mutex_set_max (U32 max)
		303	$int = $env->mutex_set_align (U32 align)
		304
		305	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		306	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		307
		308	=head4 Example:
		309
		310	use AnyEvent;
		311	use BDB;
		312
		313	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		314	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		315
		316	BDB::min_parallel 8;
		317
		318	my $env = db_env_create;
		319
		320	mkdir "bdtest", 0700;
		321	db_env_open
		322	$env,
		323	"bdtest",
		324	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		325	0600;
		326
		327	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		328
		329
		330	=head3 DB/database methods
		331
		332	Methods available on DB/$db handles:
		333
		334	DESTROY (DB_ornull *db)
		335	CODE:
		336	if (db)
		337	{
		338	SV env = (SV )db->app_private;
		339	db->close (db, 0);
		340	SvREFCNT_dec (env);
		341	}
		342
		343	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		344	$int = $db->set_flags (U32 flags)
		345	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		346	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		347	Hash: DUP DUPSORT
		348	Queue: INORDER
		349	Recno: RENUMBER SNAPSHOT
		350
		351	$int = $db->set_encrypt (const char *password, U32 flags)
		352	$int = $db->set_lorder (int lorder)
		353	$int = $db->set_bt_minkey (U32 minkey)
		354	$int = $db->set_re_delim (int delim)
		355	$int = $db->set_re_pad (int re_pad)
		356	$int = $db->set_re_source (char *source)
		357	$int = $db->set_re_len (U32 re_len)
		358	$int = $db->set_h_ffactor (U32 h_ffactor)
		359	$int = $db->set_h_nelem (U32 h_nelem)
		360	$int = $db->set_q_extentsize (U32 extentsize)
		361
		362	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		363	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		364	$seq = $db->sequence (U32 flags = 0)
		365
		366	=head4 Example:
		367
		368	my $db = db_create $env;
		369	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		370
		371	for (1..1000) {
		372	db_put $db, undef, "key $_", "data $_";
		373
		374	db_key_range $db, undef, "key $_", my $keyrange;
		375	my ($lt, $eq, $gt) = @$keyrange;
		376	}
		377
		378	db_del $db, undef, "key $_" for 1..1000;
		379
		380	db_sync $db;
		381
		382
		383	=head3 DB_TXN/transaction methods
		384
		385	Methods available on DB_TXN/$txn handles:
		386
		387	DESTROY (DB_TXN_ornull *txn)
		388	CODE:
		389	if (txn)
		390	txn->abort (txn);
		391
		392	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		393	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		394
		395	$bool = $txn->failed
		396	# see db_txn_finish documentation, above
		397
		398
		399	=head3 DBC/cursor methods
		400
		401	Methods available on DBC/$dbc handles:
		402
		403	DESTROY (DBC_ornull *dbc)
		404	CODE:
		405	if (dbc)
		406	dbc->c_close (dbc);
		407
		408	$int = $cursor->set_priority ($priority = PRIORITY_*)
		409
		410	=head4 Example:
		411
		412	my $c = $db->cursor;
		413
		414	for (;;) {
		415	db_c_get $c, my $key, my $data, BDB::NEXT;
		416	warn "<$!,$key,$data>";
		417	last if $!;
		418	}
		419
		420	db_c_close $c;
		421
		422
		423	=head3 DB_SEQUENCE/sequence methods
		424
		425	Methods available on DB_SEQUENCE/$seq handles:
		426
		427	DESTROY (DB_SEQUENCE_ornull *seq)
		428	CODE:
		429	if (seq)
		430	seq->close (seq, 0);
		431
		432	$int = $seq->initial_value (db_seq_t value)
		433	$int = $seq->set_cachesize (U32 size)
		434	$int = $seq->set_flags (U32 flags)
		435	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		436	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		437
		438	=head4 Example:
		439
		440	my $seq = $db->sequence;
		441
		442	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		443	db_sequence_get $seq, undef, 1, my $value;
		444
		445
80	=head2 SUPPORT FUNCTIONS	446	=head2 SUPPORT FUNCTIONS
81		447
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	448	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		449
84	=over 4	450	=over 4
85		451
		452	=item $msg = BDB::strerror [$errno]
		453
		454	Returns the string corresponding to the given errno value. If no argument
		455	is given, use C<$!>.
		456
		457	Note that the BDB module also patches the C<$!> variable directly, so you
		458	should be able to get a bdb error string by simply stringifying C<$!>.
		459
86	=item $fileno = BDB::AIO::poll_fileno	460	=item $fileno = BDB::poll_fileno
87		461
88	Return the I<request result pipe file descriptor>. This filehandle must be	462	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	463	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	464	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	465	to call C<poll_cb> to check the results.
92		466
93	See C<poll_cb> for an example.	467	See C<poll_cb> for an example.
94		468
95	=item BDB::AIO::poll_cb	469	=item BDB::poll_cb
96		470
97	Process some outstanding events on the result pipe. You have to call this	471	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	472	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	473	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>.	474	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		475
102	If not all requests were processed for whatever reason, the filehandle	476	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	477	will still be ready when C<poll_cb> returns.
104		478
105	Example: Install an Event watcher that automatically calls	479	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	480	BDB::poll_cb with high priority:
107		481
108	Event->io (fd => BDB::AIO::poll_fileno,	482	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	483	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	484	cb => \&BDB::poll_cb);
111		485
112	=item BDB::AIO::max_poll_reqs $nreqs	486	=item BDB::max_poll_reqs $nreqs
113		487
114	=item BDB::AIO::max_poll_time $seconds	488	=item BDB::max_poll_time $seconds
115		489
116	These set the maximum number of requests (default C<0>, meaning infinity)	490	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	491	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	492	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	493	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	494	of time C<poll_cb> is allowed to use).
121		495
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	496	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	497	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	498	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	502	interactiveness when perl is not fast enough to process all requests in
129	time.	503	time.
130		504
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	505	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		506
133	Example: Install an Event watcher that automatically calls	507	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	508	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	509	program get the CPU sometimes even under high load.
136		510
137	# try not to spend much more than 0.1s in poll_cb	511	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	512	BDB::max_poll_time 0.1;
139		513
140	# use a low priority so other tasks have priority	514	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		515
145	=item BDB::AIO::poll_wait	516	=item BDB::poll_wait
146		517
147	If there are any outstanding requests and none of them in the result	518	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	519	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	520	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	521	synchronously wait for some requests to finish).
151		522
152	See C<nreqs> for an example.	523	See C<nreqs> for an example.
153		524
154	=item BDB::AIO::poll	525	=item BDB::poll
155		526
156	Waits until some requests have been handled.	527	Waits until some requests have been handled.
157		528
158	Returns the number of requests processed, but is otherwise strictly	529	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	530	equivalent to:
160		531
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	532	BDB::poll_wait, BDB::poll_cb
162		533
163	=item BDB::AIO::flush	534	=item BDB::flush
164		535
165	Wait till all outstanding AIO requests have been handled.	536	Wait till all outstanding BDB requests have been handled.
166		537
167	Strictly equivalent to:	538	Strictly equivalent to:
168		539
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	540	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	541	while BDB::nreqs;
		542
		543	=back
		544
		545	=head3 VERSION CHECKING
		546
		547	BerkeleyDB comes in various versions, many of them have minor
		548	incompatibilities. This means that traditional "at least version x.x"
		549	checks are often not sufficient.
		550
		551	Example: set the log_autoremove option in a way compatible with <v.47 and
		552	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		553	bug when the symbol isn't available.
		554
		555	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		556	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		557
		558	=over 4
		559
		560	=item BDB::VERSION
		561
		562	The C<BDB::VERSION> function, when called without arguments, returns the
		563	Berkeley DB version as a v-string (usually with 3 components). You should
		564	use C<lt> and C<ge> operators exclusively to make comparisons.
		565
		566	Example: check for at least version 4.7.
		567
		568	BDB::VERSION ge v4.7 or die;
		569
		570	=item BDB::VERSION min-version
		571
		572	Returns true if the BDB version is at least the given version (specified
		573	as a v-string), false otherwise.
		574
		575	Example: check for at least version 4.5.
		576
		577	BDB::VERSION v4.7 or die;
		578
		579	=item BDB::VERSION min-version, max-version
		580
		581	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		582	and less then C<max-version>.
		583
		584	Example: check wether version is strictly less then v4.7.
		585
		586	BDB::VERSION v0, v4.7
		587	or die "version 4.7 is not yet supported";
		588
		589	=back
		590
		591	=cut
		592
		593	sub VERSION {
		594	if (@_ > 0) {
		595	return undef if VERSION_v lt $_[0];
		596	if (@_ > 1) {
		597	return undef if VERSION_v ge $_[1];
		598	}
		599	}
		600
		601	VERSION_v
		602	}
171		603
172	=head3 CONTROLLING THE NUMBER OF THREADS	604	=head3 CONTROLLING THE NUMBER OF THREADS
173		605
		606	=over 4
		607
174	=item BDB::AIO::min_parallel $nthreads	608	=item BDB::min_parallel $nthreads
175		609
176	Set the minimum number of AIO threads to C<$nthreads>. The current	610	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	611	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	612	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	613	however, is unlimited).
180		614
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	615	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	616	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	617	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.	618	is in the cache and could have been processed faster by a single thread.
185		619
186	It is recommended to keep the number of threads relatively low, as some	620	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	623	versions, 4-32 threads should be fine.
190		624
191	Under most circumstances you don't need to call this function, as the	625	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.	626	module selects a default that is suitable for low to moderate load.
193		627
194	=item BDB::AIO::max_parallel $nthreads	628	=item BDB::max_parallel $nthreads
195		629
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	630	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	631	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	632	them. This function blocks until the limit is reached.
199		633
200	While C<$nthreads> are zero, aio requests get queued but not executed	634	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	635	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	637	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.	638	that all threads are killed and that there are no outstanding requests.
205		639
206	Under normal circumstances you don't need to call this function.	640	Under normal circumstances you don't need to call this function.
207		641
208	=item BDB::AIO::max_idle $nthreads	642	=item BDB::max_idle $nthreads
209		643
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	644	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	645	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	646	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	647	idle, it will free its resources and exit.
…		…
218		652
219	The default is probably ok in most situations, especially if thread	653	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	654	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	655	want to use larger values.
222		656
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	657	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		658
225	This is a very bad function to use in interactive programs because it	659	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	660	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	661	use an C<aio_group> together with a feed callback.
228		662
…		…
236		670
237	You can still queue as many requests as you want. Therefore,	671	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	672	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).	673	as a stop gap to shield against fatal memory overflow (with large values).
240		674
		675	=item BDB::set_sync_prepare $cb
		676
		677	Sets a callback that is called whenever a request is created without an
		678	explicit callback. It has to return two code references. The first is used
		679	as the request callback (it should save the return status), and the second
		680	is called to wait until the first callback has been called (it must set
		681	C<$!> to the return status).
		682
		683	This mechanism can be used to include BDB into other event mechanisms,
		684	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		685
		686	The default implementation works like this:
		687
		688	sub {
		689	my $status;
		690	(
		691	sub { $status = $! },
		692	sub { BDB::poll while !defined $status; $! = $status },
		693	)
		694	}
		695
		696	It simply blocks the process till the request has finished and then sets
		697	C<$!> to the return value. This means that if you don't use a callback,
		698	BDB will simply fall back to synchronous operations.
		699
		700	=back
		701
241	=head3 STATISTICAL INFORMATION	702	=head3 STATISTICAL INFORMATION
242		703
		704	=over 4
		705
243	=item BDB::AIO::nreqs	706	=item BDB::nreqs
244		707
245	Returns the number of requests currently in the ready, execute or pending	708	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).	709	states (i.e. for which their callback has not been invoked yet).
247		710
248	Example: wait till there are no outstanding requests anymore:	711	Example: wait till there are no outstanding requests anymore:
249		712
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	713	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	714	while BDB::nreqs;
252		715
253	=item BDB::AIO::nready	716	=item BDB::nready
254		717
255	Returns the number of requests currently in the ready state (not yet	718	Returns the number of requests currently in the ready state (not yet
256	executed).	719	executed).
257		720
258	=item BDB::AIO::npending	721	=item BDB::npending
259		722
260	Returns the number of requests currently in the pending state (executed,	723	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	724	but not yet processed by poll_cb).
262		725
263	=back	726	=back
264		727
265	=cut	728	=cut
266		729
267	# support function to convert a fd into a perl filehandle	730	set_sync_prepare {
268	sub _fd2fh {	731	my $status;
269	return undef if $_[0] < 0;	732	(
270		733	sub {
271	# try to generate nice filehandles	734	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	735	},
273	local *$sym;	736	sub {
274		737	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	738	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	739	},
277	or open *$sym, ">&=$_[0]" # or this	740	)
278	or return undef;	741	};
279
280	*$sym
281	}
282		742
283	min_parallel 8;	743	min_parallel 8;
284		744
285	END { flush }	745	END { flush }
286		746
…		…
288		748
289	=head2 FORK BEHAVIOUR	749	=head2 FORK BEHAVIOUR
290		750
291	This module should do "the right thing" when the process using it forks:	751	This module should do "the right thing" when the process using it forks:
292		752
293	Before the fork, IO::AIO enters a quiescent state where no requests	753	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	754	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	755	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	756	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	757	(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	758	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	759	parent process has been reached again.
300		760
301	In short: the parent will, after a short pause, continue as if fork had	761	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	762	not been called, while the child will act as if BDB has not been used
303	yet.	763	yet.
		764
		765	Win32 note: there is no fork on win32, and perls emulation of it is too
		766	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		767	yet, switch to a more capable platform.
304		768
305	=head2 MEMORY USAGE	769	=head2 MEMORY USAGE
306		770
307	Per-request usage:	771	Per-request usage:
308		772
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	774	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	775	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	776	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.	777	will consume memory till the request has entered the done state.
314		778
315	This is now awfully much, so queuing lots of requests is not usually a	779	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	780	problem.
317		781
318	Per-thread usage:	782	Per-thread usage:
319		783
320	In the execution phase, some aio requests require more memory for	784	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	785	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	786	structures (usually around 16k-128k, depending on the OS).
323		787
324	=head1 KNOWN BUGS	788	=head1 KNOWN BUGS
325		789
326	Known bugs will be fixed in the next release.	790	Known bugs will be fixed in the next release, except:
		791
		792	If you use a transaction in any request, and the request returns
		793	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		794	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		795	above.
327		796
328	=head1 SEE ALSO	797	=head1 SEE ALSO
329		798
330	L<Coro::AIO>.	799	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		800	syntax), L<IO::AIO> (nice to have).
331		801
332	=head1 AUTHOR	802	=head1 AUTHOR
333		803
334	Marc Lehmann <schmorp@schmorp.de>	804	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	805	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 1.40 by root, Tue Jul 8 08:35:12 2008 UTC

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Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.40 by root, Tue Jul 8 08:35:12 2008 UTC