[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 1.41 by root, Wed Jul 9 12:15:36 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	Most C<SV *> types are generic perl scalars (for input and output of data
		166	values).
		167
		168	The various C<DB_ENV> etc. arguments are handles return by
		169	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		170	appended C<_ornull> this means they are optional and you can pass C<undef>
		171	for them, resulting a NULL pointer on the C level.
		172
		173	The C<SV *callback> is the optional callback function to call when the
		174	request is completed. This last callback argument is special: the callback
		175	is simply the last argument passed. If there are "optional" arguments
		176	before the callback they can be left out. The callback itself can be left
		177	out or specified as C<undef>, in which case the function will be executed
		178	synchronously.
		179
		180	For example, C<db_env_txn_checkpoint> usually is called with all integer
		181	arguments zero. These can be left out, so all of these specify a call
		182	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		183	callback to be called:
		184
		185	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		186	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		187	db_env_txn_checkpoint $db_env, sub { };
		188
		189	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		190	executed synchronously:
		191
		192	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		193	db_env_txn_checkpoint $db_env, 0, 0, 0;
		194	db_env_txn_checkpoint $db_env, 0;
		195
		196	=head3 BDB functions
		197
		198	Functions in the BDB namespace, exported by default:
		199
		200	$env = db_env_create (U32 env_flags = 0)
		201	flags: RPCCLIENT
		202
		203	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		204	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
		205	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		206	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		207	flags: FORCE
		208	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		209	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		210	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		211	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		212	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		213	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)
		214
		215	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		216	flags: XA_CREATE
		217
		218	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)
		219	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		220	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		221	flags: DB_NOSYNC
		222	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		223	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)
		224	flags: FREELIST_ONLY FREE_SPACE
		225	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		226	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		227	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		228	flags: APPEND NODUPDATA NOOVERWRITE
		229	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		230	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		231	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		232	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		233	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		234	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		235	flags: TXN_NOSYNC TXN_SYNC
		236	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		237
		238	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		239	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		240	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		241	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		242	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		243	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
		244	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		245	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		246
		247	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		248	flags: CREATE EXCL
		249	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		250	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)
		251	flags: TXN_NOSYNC
		252	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		253	flags: TXN_NOSYNC
		254
		255	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		256
		257	This is not actually a Berkeley DB function but a BDB module
		258	extension. The background for this exytension is: It is very annoying to
		259	have to check every single BDB function for error returns and provide a
		260	codepath out of your transaction. While the BDB module still makes this
		261	possible, it contains the following extensions:
		262
		263	When a transaction-protected function returns any operating system
		264	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		265	transaction. This flag is also set by Berkeley DB functions themselves
		266	when an operation fails with LOCK_DEADLOCK, and it causes all further
		267	operations on that transaction (including C<db_txn_commit>) to fail.
		268
		269	The C<db_txn_finish> request will look at this flag, and, if it is set,
		270	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		271	if it isn't set to something else yet). If it isn't set, it will call
		272	C<db_txn_commit> and return the error normally.
		273
		274	How to use this? Easy: just write your transaction normally:
		275
		276	my $txn = $db_env->txn_begin;
		277	db_get $db, $txn, "key", my $data;
		278	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		279	db_txn_finish $txn;
		280	die "transaction failed" if $!;
		281
		282	That is, handle only the expected errors. If something unexpected happens
		283	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		284	requests (db_put in this case) will simply be skipped (they will fail with
		285	LOCK_DEADLOCK) and the transaction will be aborted.
		286
		287	You can use the C<< $txn->failed >> method to check wether a transaction
		288	has failed in this way and abort further processing (excluding
		289	C<db_txn_finish>).
		290
		291	=head3 DB_ENV/database environment methods
		292
		293	Methods available on DB_ENV/$env handles:
		294
		295	DESTROY (DB_ENV_ornull *env)
		296	CODE:
		297	if (env)
		298	env->close (env, 0);
		299
		300	$int = $env->set_data_dir (const char *dir)
		301	$int = $env->set_tmp_dir (const char *dir)
		302	$int = $env->set_lg_dir (const char *dir)
		303	$int = $env->set_shm_key (long shm_key)
		304	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		305	$int = $env->set_flags (U32 flags, int onoff = 1)
		306	$int = $env->log_set_config (U32 flags, int onoff = 1) [v4.7]
		307	$int = $env->set_intermediate_dir_mode (const char *modestring) [v4.7]
		308	$env->set_errfile (FILE *errfile = 0)
		309	$env->set_msgfile (FILE *msgfile = 0)
		310	$int = $env->set_verbose (U32 which, int onoff = 1)
		311	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		312	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		313	$int = $env->set_mp_max_openfd (int maxopenfd);
		314	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		315	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		316	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		317	$int = $env->set_lk_max_lockers (U32 max)
		318	$int = $env->set_lk_max_locks (U32 max)
		319	$int = $env->set_lk_max_objects (U32 max)
		320	$int = $env->set_lg_bsize (U32 max)
		321	$int = $env->set_lg_max (U32 max)
		322	$int = $env->mutex_set_increment (U32 increment)
		323	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		324	$int = $env->mutex_set_max (U32 max)
		325	$int = $env->mutex_set_align (U32 align)
		326
		327	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		328	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		329
		330	=head4 Example:
		331
		332	use AnyEvent;
		333	use BDB;
		334
		335	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		336	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		337
		338	BDB::min_parallel 8;
		339
		340	my $env = db_env_create;
		341
		342	mkdir "bdtest", 0700;
		343	db_env_open
		344	$env,
		345	"bdtest",
		346	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		347	0600;
		348
		349	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		350
		351
		352	=head3 DB/database methods
		353
		354	Methods available on DB/$db handles:
		355
		356	DESTROY (DB_ornull *db)
		357	CODE:
		358	if (db)
		359	{
		360	SV env = (SV )db->app_private;
		361	db->close (db, 0);
		362	SvREFCNT_dec (env);
		363	}
		364
		365	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		366	$int = $db->set_flags (U32 flags)
		367	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		368	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		369	Hash: DUP DUPSORT
		370	Queue: INORDER
		371	Recno: RENUMBER SNAPSHOT
		372
		373	$int = $db->set_encrypt (const char *password, U32 flags)
		374	$int = $db->set_lorder (int lorder)
		375	$int = $db->set_bt_minkey (U32 minkey)
		376	$int = $db->set_re_delim (int delim)
		377	$int = $db->set_re_pad (int re_pad)
		378	$int = $db->set_re_source (char *source)
		379	$int = $db->set_re_len (U32 re_len)
		380	$int = $db->set_h_ffactor (U32 h_ffactor)
		381	$int = $db->set_h_nelem (U32 h_nelem)
		382	$int = $db->set_q_extentsize (U32 extentsize)
		383
		384	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		385	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		386	$seq = $db->sequence (U32 flags = 0)
		387
		388	=head4 Example:
		389
		390	my $db = db_create $env;
		391	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		392
		393	for (1..1000) {
		394	db_put $db, undef, "key $_", "data $_";
		395
		396	db_key_range $db, undef, "key $_", my $keyrange;
		397	my ($lt, $eq, $gt) = @$keyrange;
		398	}
		399
		400	db_del $db, undef, "key $_" for 1..1000;
		401
		402	db_sync $db;
		403
		404
		405	=head3 DB_TXN/transaction methods
		406
		407	Methods available on DB_TXN/$txn handles:
		408
		409	DESTROY (DB_TXN_ornull *txn)
		410	CODE:
		411	if (txn)
		412	txn->abort (txn);
		413
		414	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		415	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		416
		417	$bool = $txn->failed
		418	# see db_txn_finish documentation, above
		419
		420
		421	=head3 DBC/cursor methods
		422
		423	Methods available on DBC/$dbc handles:
		424
		425	DESTROY (DBC_ornull *dbc)
		426	CODE:
		427	if (dbc)
		428	dbc->c_close (dbc);
		429
		430	$int = $cursor->set_priority ($priority = PRIORITY_*)
		431
		432	=head4 Example:
		433
		434	my $c = $db->cursor;
		435
		436	for (;;) {
		437	db_c_get $c, my $key, my $data, BDB::NEXT;
		438	warn "<$!,$key,$data>";
		439	last if $!;
		440	}
		441
		442	db_c_close $c;
		443
		444
		445	=head3 DB_SEQUENCE/sequence methods
		446
		447	Methods available on DB_SEQUENCE/$seq handles:
		448
		449	DESTROY (DB_SEQUENCE_ornull *seq)
		450	CODE:
		451	if (seq)
		452	seq->close (seq, 0);
		453
		454	$int = $seq->initial_value (db_seq_t value)
		455	$int = $seq->set_cachesize (U32 size)
		456	$int = $seq->set_flags (U32 flags)
		457	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		458	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		459
		460	=head4 Example:
		461
		462	my $seq = $db->sequence;
		463
		464	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		465	db_sequence_get $seq, undef, 1, my $value;
		466
		467
80	=head2 SUPPORT FUNCTIONS	468	=head2 SUPPORT FUNCTIONS
81		469
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	470	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		471
84	=over 4	472	=over 4
85		473
		474	=item $msg = BDB::strerror [$errno]
		475
		476	Returns the string corresponding to the given errno value. If no argument
		477	is given, use C<$!>.
		478
		479	Note that the BDB module also patches the C<$!> variable directly, so you
		480	should be able to get a bdb error string by simply stringifying C<$!>.
		481
86	=item $fileno = BDB::AIO::poll_fileno	482	=item $fileno = BDB::poll_fileno
87		483
88	Return the I<request result pipe file descriptor>. This filehandle must be	484	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	485	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	486	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	487	to call C<poll_cb> to check the results.
92		488
93	See C<poll_cb> for an example.	489	See C<poll_cb> for an example.
94		490
95	=item BDB::AIO::poll_cb	491	=item BDB::poll_cb
96		492
97	Process some outstanding events on the result pipe. You have to call this	493	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	494	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	495	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>.	496	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		497
102	If not all requests were processed for whatever reason, the filehandle	498	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	499	will still be ready when C<poll_cb> returns.
104		500
105	Example: Install an Event watcher that automatically calls	501	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	502	BDB::poll_cb with high priority:
107		503
108	Event->io (fd => BDB::AIO::poll_fileno,	504	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	505	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	506	cb => \&BDB::poll_cb);
111		507
112	=item BDB::AIO::max_poll_reqs $nreqs	508	=item BDB::max_poll_reqs $nreqs
113		509
114	=item BDB::AIO::max_poll_time $seconds	510	=item BDB::max_poll_time $seconds
115		511
116	These set the maximum number of requests (default C<0>, meaning infinity)	512	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	513	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	514	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	515	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	516	of time C<poll_cb> is allowed to use).
121		517
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	518	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	519	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	520	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	524	interactiveness when perl is not fast enough to process all requests in
129	time.	525	time.
130		526
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	527	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		528
133	Example: Install an Event watcher that automatically calls	529	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	530	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	531	program get the CPU sometimes even under high load.
136		532
137	# try not to spend much more than 0.1s in poll_cb	533	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	534	BDB::max_poll_time 0.1;
139		535
140	# use a low priority so other tasks have priority	536	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		537
145	=item BDB::AIO::poll_wait	538	=item BDB::poll_wait
146		539
147	If there are any outstanding requests and none of them in the result	540	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	541	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	542	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	543	synchronously wait for some requests to finish).
151		544
152	See C<nreqs> for an example.	545	See C<nreqs> for an example.
153		546
154	=item BDB::AIO::poll	547	=item BDB::poll
155		548
156	Waits until some requests have been handled.	549	Waits until some requests have been handled.
157		550
158	Returns the number of requests processed, but is otherwise strictly	551	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	552	equivalent to:
160		553
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	554	BDB::poll_wait, BDB::poll_cb
162		555
163	=item BDB::AIO::flush	556	=item BDB::flush
164		557
165	Wait till all outstanding AIO requests have been handled.	558	Wait till all outstanding BDB requests have been handled.
166		559
167	Strictly equivalent to:	560	Strictly equivalent to:
168		561
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	562	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	563	while BDB::nreqs;
		564
		565	=back
		566
		567	=head3 VERSION CHECKING
		568
		569	BerkeleyDB comes in various versions, many of them have minor
		570	incompatibilities. This means that traditional "at least version x.x"
		571	checks are often not sufficient.
		572
		573	Example: set the log_autoremove option in a way compatible with <v.47 and
		574	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		575	bug when the symbol isn't available.
		576
		577	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		578	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		579
		580	=over 4
		581
		582	=item BDB::VERSION
		583
		584	The C<BDB::VERSION> function, when called without arguments, returns the
		585	Berkeley DB version as a v-string (usually with 3 components). You should
		586	use C<lt> and C<ge> operators exclusively to make comparisons.
		587
		588	Example: check for at least version 4.7.
		589
		590	BDB::VERSION ge v4.7 or die;
		591
		592	=item BDB::VERSION min-version
		593
		594	Returns true if the BDB version is at least the given version (specified
		595	as a v-string), false otherwise.
		596
		597	Example: check for at least version 4.5.
		598
		599	BDB::VERSION v4.7 or die;
		600
		601	=item BDB::VERSION min-version, max-version
		602
		603	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		604	and less then C<max-version>.
		605
		606	Example: check wether version is strictly less then v4.7.
		607
		608	BDB::VERSION v0, v4.7
		609	or die "version 4.7 is not yet supported";
		610
		611	=back
		612
		613	=cut
		614
		615	sub VERSION {
		616	if (@_ > 0) {
		617	return undef if VERSION_v lt $_[0];
		618	if (@_ > 1) {
		619	return undef if VERSION_v ge $_[1];
		620	}
		621	}
		622
		623	VERSION_v
		624	}
171		625
172	=head3 CONTROLLING THE NUMBER OF THREADS	626	=head3 CONTROLLING THE NUMBER OF THREADS
173		627
		628	=over 4
		629
174	=item BDB::AIO::min_parallel $nthreads	630	=item BDB::min_parallel $nthreads
175		631
176	Set the minimum number of AIO threads to C<$nthreads>. The current	632	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	633	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	634	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	635	however, is unlimited).
180		636
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	637	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	638	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	639	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.	640	is in the cache and could have been processed faster by a single thread.
185		641
186	It is recommended to keep the number of threads relatively low, as some	642	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	645	versions, 4-32 threads should be fine.
190		646
191	Under most circumstances you don't need to call this function, as the	647	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.	648	module selects a default that is suitable for low to moderate load.
193		649
194	=item BDB::AIO::max_parallel $nthreads	650	=item BDB::max_parallel $nthreads
195		651
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	652	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	653	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	654	them. This function blocks until the limit is reached.
199		655
200	While C<$nthreads> are zero, aio requests get queued but not executed	656	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	657	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	659	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.	660	that all threads are killed and that there are no outstanding requests.
205		661
206	Under normal circumstances you don't need to call this function.	662	Under normal circumstances you don't need to call this function.
207		663
208	=item BDB::AIO::max_idle $nthreads	664	=item BDB::max_idle $nthreads
209		665
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	666	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	667	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	668	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	669	idle, it will free its resources and exit.
…		…
218		674
219	The default is probably ok in most situations, especially if thread	675	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	676	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	677	want to use larger values.
222		678
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	679	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		680
225	This is a very bad function to use in interactive programs because it	681	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	682	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	683	use an C<aio_group> together with a feed callback.
228		684
…		…
236		692
237	You can still queue as many requests as you want. Therefore,	693	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	694	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).	695	as a stop gap to shield against fatal memory overflow (with large values).
240		696
		697	=item BDB::set_sync_prepare $cb
		698
		699	Sets a callback that is called whenever a request is created without an
		700	explicit callback. It has to return two code references. The first is used
		701	as the request callback (it should save the return status), and the second
		702	is called to wait until the first callback has been called (it must set
		703	C<$!> to the return status).
		704
		705	This mechanism can be used to include BDB into other event mechanisms,
		706	such as L<AnyEvent::BDB> or L<Coro::BDB>.
		707
		708	The default implementation works like this:
		709
		710	sub {
		711	my $status;
		712	(
		713	sub { $status = $! },
		714	sub { BDB::poll while !defined $status; $! = $status },
		715	)
		716	}
		717
		718	It simply blocks the process till the request has finished and then sets
		719	C<$!> to the return value. This means that if you don't use a callback,
		720	BDB will simply fall back to synchronous operations.
		721
		722	=back
		723
241	=head3 STATISTICAL INFORMATION	724	=head3 STATISTICAL INFORMATION
242		725
		726	=over 4
		727
243	=item BDB::AIO::nreqs	728	=item BDB::nreqs
244		729
245	Returns the number of requests currently in the ready, execute or pending	730	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).	731	states (i.e. for which their callback has not been invoked yet).
247		732
248	Example: wait till there are no outstanding requests anymore:	733	Example: wait till there are no outstanding requests anymore:
249		734
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	735	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	736	while BDB::nreqs;
252		737
253	=item BDB::AIO::nready	738	=item BDB::nready
254		739
255	Returns the number of requests currently in the ready state (not yet	740	Returns the number of requests currently in the ready state (not yet
256	executed).	741	executed).
257		742
258	=item BDB::AIO::npending	743	=item BDB::npending
259		744
260	Returns the number of requests currently in the pending state (executed,	745	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	746	but not yet processed by poll_cb).
262		747
263	=back	748	=back
264		749
265	=cut	750	=cut
266		751
267	# support function to convert a fd into a perl filehandle	752	set_sync_prepare {
268	sub _fd2fh {	753	my $status;
269	return undef if $_[0] < 0;	754	(
270		755	sub {
271	# try to generate nice filehandles	756	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	757	},
273	local *$sym;	758	sub {
274		759	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	760	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	761	},
277	or open *$sym, ">&=$_[0]" # or this	762	)
278	or return undef;	763	};
279
280	*$sym
281	}
282		764
283	min_parallel 8;	765	min_parallel 8;
284		766
285	END { flush }	767	END { flush }
286		768
…		…
288		770
289	=head2 FORK BEHAVIOUR	771	=head2 FORK BEHAVIOUR
290		772
291	This module should do "the right thing" when the process using it forks:	773	This module should do "the right thing" when the process using it forks:
292		774
293	Before the fork, IO::AIO enters a quiescent state where no requests	775	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	776	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	777	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	778	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	779	(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	780	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	781	parent process has been reached again.
300		782
301	In short: the parent will, after a short pause, continue as if fork had	783	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	784	not been called, while the child will act as if BDB has not been used
303	yet.	785	yet.
		786
		787	Win32 note: there is no fork on win32, and perls emulation of it is too
		788	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		789	yet, switch to a more capable platform.
304		790
305	=head2 MEMORY USAGE	791	=head2 MEMORY USAGE
306		792
307	Per-request usage:	793	Per-request usage:
308		794
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	796	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	797	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	798	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.	799	will consume memory till the request has entered the done state.
314		800
315	This is now awfully much, so queuing lots of requests is not usually a	801	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	802	problem.
317		803
318	Per-thread usage:	804	Per-thread usage:
319		805
320	In the execution phase, some aio requests require more memory for	806	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	807	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	808	structures (usually around 16k-128k, depending on the OS).
323		809
324	=head1 KNOWN BUGS	810	=head1 KNOWN BUGS
325		811
326	Known bugs will be fixed in the next release.	812	Known bugs will be fixed in the next release, except:
		813
		814	If you use a transaction in any request, and the request returns
		815	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		816	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		817	above.
327		818
328	=head1 SEE ALSO	819	=head1 SEE ALSO
329		820
330	L<Coro::AIO>.	821	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		822	syntax), L<IO::AIO> (nice to have).
331		823
332	=head1 AUTHOR	824	=head1 AUTHOR
333		825
334	Marc Lehmann <schmorp@schmorp.de>	826	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	827	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing BDB/BDB.pm (file contents): Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs. Revision 1.41 by root, Wed Jul 9 12:15:36 2008 UTC

Diff Legend

Comparing BDB/BDB.pm (file contents):
Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.41 by root, Wed Jul 9 12:15:36 2008 UTC