[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 1.67 by root, Tue Feb 2 04:07:06 2016 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 integration 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	use common::sense;
63	use strict 'vars';
64		109
65	use base 'Exporter';	110	use base 'Exporter';
66		111
		112	our $VERSION;
		113
67	BEGIN {	114	BEGIN {
68	our $VERSION = '0.1';	115	$VERSION = '1.91';
69		116
70	our @BDB_REQ = qw();	117	our @BDB_REQ = qw(
		118	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		119	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
		120	db_env_log_archive db_env_reset_lsn
		121	db_open db_close db_compact db_sync db_verify db_upgrade
		122	db_put db_exists db_get db_pget db_del db_key_range
		123	db_txn_commit db_txn_abort db_txn_finish
		124	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		125	db_sequence_open db_sequence_close
		126	db_sequence_get db_sequence_remove
		127	);
		128	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		129	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	130	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	131	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	132	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	133	max_poll_time max_poll_reqs
		134	);
75		135
76	require XSLoader;	136	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	137	XSLoader::load ("BDB", $VERSION);
78	}	138	}
79		139
		140	=head1 BERKELEYDB FUNCTIONS
		141
		142	All of these are functions. The create functions simply return a new
		143	object and never block. All the remaining functions take an optional
		144	callback as last argument. If it is missing, then the function will be
		145	executed synchronously. In both cases, C<$!> will reflect the return value
		146	of the function.
		147
		148	BDB functions that cannot block (mostly functions that manipulate
		149	settings) are method calls on the relevant objects, so the rule of thumb
		150	is: if it's a method, it's not blocking, if it's a function, it takes a
		151	callback as last argument.
		152
		153	In the following, C<$int> signifies an integer return value,
		154	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		155	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		156	floating point value.
		157
		158	Most C<SV *> types are generic perl scalars (for input and output of data
		159	values).
		160
		161	The various C<DB_ENV> etc. arguments are handles return by
		162	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		163	appended C<_ornull> this means they are optional and you can pass C<undef>
		164	for them, resulting a NULL pointer on the C level.
		165
		166	The C<SV *callback> is the optional callback function to call when the
		167	request is completed. This last callback argument is special: the callback
		168	is simply the last argument passed. If there are "optional" arguments
		169	before the callback they can be left out. The callback itself can be left
		170	out or specified as C<undef>, in which case the function will be executed
		171	synchronously.
		172
		173	For example, C<db_env_txn_checkpoint> usually is called with all integer
		174	arguments zero. These can be left out, so all of these specify a call
		175	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		176	callback to be called:
		177
		178	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		179	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		180	db_env_txn_checkpoint $db_env, sub { };
		181
		182	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		183	executed synchronously:
		184
		185	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		186	db_env_txn_checkpoint $db_env, 0, 0, 0;
		187	db_env_txn_checkpoint $db_env, 0;
		188
		189	=head2 BDB functions
		190
		191	Functions in the BDB namespace, exported by default:
		192
		193	$env = db_env_create (U32 env_flags = 0)
		194	flags: RPCCLIENT
		195
		196	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = 0)
		197	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
		198	db_env_close (DB_ENV env, U32 flags = 0, SV callback = 0)
		199	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = 0)
		200	flags: FORCE
		201	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = 0)
		202	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		203	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = 0)
		204	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = 0)
		205	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = 0)
		206	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = 0)
		207	db_env_log_archive (DB_ENV env, SV listp, U32 flags = 0, SV *callback = 0)
		208	db_env_lsn_reset (DB_ENV env, bdb_filename db, U32 flags = 0, SV callback = 0)
		209
		210	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		211	flags: XA_CREATE
		212
		213	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = 0)
		214	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		215	db_close (DB db, U32 flags = 0, SV callback = 0)
		216	flags: DB_NOSYNC
		217	db_verify (DB db, bdb_filename file, bdb_filename database = 0, SV dummy = 0, U32 flags = 0, SV *callback = 0)
		218	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = 0)
		219	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 = 0)
		220	flags: FREELIST_ONLY FREE_SPACE
		221	db_sync (DB db, U32 flags = 0, SV callback = 0)
		222	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = 0)
		223	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = 0)
		224	flags: APPEND NODUPDATA NOOVERWRITE
		225	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0) (v4.6)
		226	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = 0)
		227	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		228	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = 0)
		229	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		230	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0)
		231	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = 0)
		232	flags: TXN_NOSYNC TXN_SYNC
		233	db_txn_abort (DB_TXN txn, SV callback = 0)
		234
		235	db_c_close (DBC dbc, SV callback = 0)
		236	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = 0)
		237	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = 0)
		238	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		239	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = 0)
		240	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
		241	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = 0)
		242	db_c_del (DBC dbc, U32 flags = 0, SV callback = 0)
		243
		244	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = 0)
		245	flags: CREATE EXCL
		246	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = 0)
		247	db_sequence_get (DB_SEQUENCE seq, DB_TXN_ornull txnid, int delta, SV seq_value, U32 flags = DB_TXN_NOSYNC, SV callback = 0)
		248	flags: TXN_NOSYNC
		249	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = 0)
		250	flags: TXN_NOSYNC
		251
		252	=head3 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = 0)
		253
		254	This is not actually a Berkeley DB function but a BDB module
		255	extension. The background for this exytension is: It is very annoying to
		256	have to check every single BDB function for error returns and provide a
		257	codepath out of your transaction. While the BDB module still makes this
		258	possible, it contains the following extensions:
		259
		260	When a transaction-protected function returns any operating system
		261	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		262	transaction. This flag is also set by Berkeley DB functions themselves
		263	when an operation fails with LOCK_DEADLOCK, and it causes all further
		264	operations on that transaction (including C<db_txn_commit>) to fail.
		265
		266	The C<db_txn_finish> request will look at this flag, and, if it is set,
		267	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		268	if it isn't set to something else yet). If it isn't set, it will call
		269	C<db_txn_commit> and return the error normally.
		270
		271	How to use this? Easy: just write your transaction normally:
		272
		273	my $txn = $db_env->txn_begin;
		274	db_get $db, $txn, "key", my $data;
		275	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		276	db_txn_finish $txn;
		277	die "transaction failed" if $!;
		278
		279	That is, handle only the expected errors. If something unexpected happens
		280	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		281	requests (db_put in this case) will simply be skipped (they will fail with
		282	LOCK_DEADLOCK) and the transaction will be aborted.
		283
		284	You can use the C<< $txn->failed >> method to check wether a transaction
		285	has failed in this way and abort further processing (excluding
		286	C<db_txn_finish>).
		287
		288
		289	=head2 DB_ENV/database environment methods
		290
		291	Methods available on DB_ENV/$env handles:
		292
		293	DESTROY (DB_ENV_ornull *env)
		294	CODE:
		295	if (env)
		296	env->close (env, 0);
		297
		298	$int = $env->set_data_dir (const char *dir)
		299	$int = $env->set_tmp_dir (const char *dir)
		300	$int = $env->set_lg_dir (const char *dir)
		301	$int = $env->set_shm_key (long shm_key)
		302	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		303	$int = $env->set_flags (U32 flags, int onoff = 1)
		304	$int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
		305	$int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
		306	$env->set_errfile (FILE *errfile = 0)
		307	$env->set_msgfile (FILE *msgfile = 0)
		308	$int = $env->set_verbose (U32 which, int onoff = 1)
		309	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		310	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		311	$int = $env->set_mp_max_openfd (int maxopenfd);
		312	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		313	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		314	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		315	$int = $env->set_lk_max_lockers (U32 max)
		316	$int = $env->set_lk_max_locks (U32 max)
		317	$int = $env->set_lk_max_objects (U32 max)
		318	$int = $env->set_lg_bsize (U32 max)
		319	$int = $env->set_lg_max (U32 max)
		320	$int = $env->mutex_set_increment (U32 increment)
		321	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		322	$int = $env->mutex_set_max (U32 max)
		323	$int = $env->mutex_set_align (U32 align)
		324
		325	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		326	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		327	$txn = $env->cdsgroup_begin; (v4.5)
		328
		329	=head3 Example:
		330
		331	use AnyEvent;
		332	use BDB;
		333
		334	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		335	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		336
		337	BDB::min_parallel 8;
		338
		339	my $env = db_env_create;
		340
		341	mkdir "bdtest", 0700;
		342	db_env_open
		343	$env,
		344	"bdtest",
		345	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		346	0600;
		347
		348	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		349
		350
		351	=head2 DB/database methods
		352
		353	Methods available on DB/$db handles:
		354
		355	DESTROY (DB_ornull *db)
		356	CODE:
		357	if (db)
		358	{
		359	SV env = (SV )db->app_private;
		360	db->close (db, 0);
		361	SvREFCNT_dec (env);
		362	}
		363
		364	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		365	$int = $db->set_flags (U32 flags)
		366	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		367	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		368	Hash: DUP DUPSORT
		369	Queue: INORDER
		370	Recno: RENUMBER SNAPSHOT
		371
		372	$int = $db->set_encrypt (const char *password, U32 flags)
		373	$int = $db->set_lorder (int lorder)
		374	$int = $db->set_bt_minkey (U32 minkey)
		375	$int = $db->set_re_delim (int delim)
		376	$int = $db->set_re_pad (int re_pad)
		377	$int = $db->set_re_source (char *source)
		378	$int = $db->set_re_len (U32 re_len)
		379	$int = $db->set_h_ffactor (U32 h_ffactor)
		380	$int = $db->set_h_nelem (U32 h_nelem)
		381	$int = $db->set_q_extentsize (U32 extentsize)
		382
		383	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		384	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		385	$seq = $db->sequence (U32 flags = 0)
		386
		387	=head3 Example:
		388
		389	my $db = db_create $env;
		390	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		391
		392	for (1..1000) {
		393	db_put $db, undef, "key $_", "data $_";
		394
		395	db_key_range $db, undef, "key $_", my $keyrange;
		396	my ($lt, $eq, $gt) = @$keyrange;
		397	}
		398
		399	db_del $db, undef, "key $_" for 1..1000;
		400
		401	db_sync $db;
		402
		403
		404	=head2 DB_TXN/transaction methods
		405
		406	Methods available on DB_TXN/$txn handles:
		407
		408	DESTROY (DB_TXN_ornull *txn)
		409	CODE:
		410	if (txn)
		411	txn->abort (txn);
		412
		413	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		414	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		415
		416	$bool = $txn->failed
		417	# see db_txn_finish documentation, above
		418
		419
		420	=head2 DBC/cursor methods
		421
		422	Methods available on DBC/$dbc handles:
		423
		424	DESTROY (DBC_ornull *dbc)
		425	CODE:
		426	if (dbc)
		427	dbc->c_close (dbc);
		428
		429	$int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
		430
		431	=head3 Example:
		432
		433	my $c = $db->cursor;
		434
		435	for (;;) {
		436	db_c_get $c, my $key, my $data, BDB::NEXT;
		437	warn "<$!,$key,$data>";
		438	last if $!;
		439	}
		440
		441	db_c_close $c;
		442
		443
		444	=head2 DB_SEQUENCE/sequence methods
		445
		446	Methods available on DB_SEQUENCE/$seq handles:
		447
		448	DESTROY (DB_SEQUENCE_ornull *seq)
		449	CODE:
		450	if (seq)
		451	seq->close (seq, 0);
		452
		453	$int = $seq->initial_value (db_seq_t value)
		454	$int = $seq->set_cachesize (U32 size)
		455	$int = $seq->set_flags (U32 flags)
		456	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		457	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		458
		459	=head3 Example:
		460
		461	my $seq = $db->sequence;
		462
		463	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		464	db_sequence_get $seq, undef, 1, my $value;
		465
		466
80	=head2 SUPPORT FUNCTIONS	467	=head1 SUPPORT FUNCTIONS
81		468
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	469	=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		470
84	=over 4	471	=over 4
85		472
		473	=item $msg = BDB::strerror [$errno]
		474
		475	Returns the string corresponding to the given errno value. If no argument
		476	is given, use C<$!>.
		477
		478	Note that the BDB module also patches the C<$!> variable directly, so you
		479	should be able to get a bdb error string by simply stringifying C<$!>.
		480
86	=item $fileno = BDB::AIO::poll_fileno	481	=item $fileno = BDB::poll_fileno
87		482
88	Return the I<request result pipe file descriptor>. This filehandle must be	483	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	484	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	485	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	486	to call C<poll_cb> to check the results.
92		487
93	See C<poll_cb> for an example.	488	See C<poll_cb> for an example.
94		489
95	=item BDB::AIO::poll_cb	490	=item BDB::poll_cb
96		491
97	Process some outstanding events on the result pipe. You have to call this	492	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	493	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	494	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>.	495	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		496
102	If not all requests were processed for whatever reason, the filehandle	497	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	498	will still be ready when C<poll_cb> returns.
104		499
105	Example: Install an Event watcher that automatically calls	500	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	501	BDB::poll_cb with high priority:
107		502
108	Event->io (fd => BDB::AIO::poll_fileno,	503	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	504	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	505	cb => \&BDB::poll_cb);
111		506
112	=item BDB::AIO::max_poll_reqs $nreqs	507	=item BDB::max_poll_reqs $nreqs
113		508
114	=item BDB::AIO::max_poll_time $seconds	509	=item BDB::max_poll_time $seconds
115		510
116	These set the maximum number of requests (default C<0>, meaning infinity)	511	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	512	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	513	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	514	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	515	of time C<poll_cb> is allowed to use).
121		516
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	517	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	518	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	519	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	523	interactiveness when perl is not fast enough to process all requests in
129	time.	524	time.
130		525
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	526	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		527
133	Example: Install an Event watcher that automatically calls	528	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	529	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	530	program get the CPU sometimes even under high load.
136		531
137	# try not to spend much more than 0.1s in poll_cb	532	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	533	BDB::max_poll_time 0.1;
139		534
140	# use a low priority so other tasks have priority	535	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		536
145	=item BDB::AIO::poll_wait	537	=item BDB::poll_wait
146		538
147	If there are any outstanding requests and none of them in the result	539	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	540	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	541	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	542	synchronously wait for some requests to finish).
151		543
152	See C<nreqs> for an example.	544	See C<nreqs> for an example.
153		545
154	=item BDB::AIO::poll	546	=item BDB::poll
155		547
156	Waits until some requests have been handled.	548	Waits until some requests have been handled.
157		549
158	Returns the number of requests processed, but is otherwise strictly	550	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	551	equivalent to:
160		552
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	553	BDB::poll_wait, BDB::poll_cb
162		554
163	=item BDB::AIO::flush	555	=item BDB::flush
164		556
165	Wait till all outstanding AIO requests have been handled.	557	Wait till all outstanding BDB requests have been handled.
166		558
167	Strictly equivalent to:	559	Strictly equivalent to:
168		560
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	561	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	562	while BDB::nreqs;
171		563
		564	=back
		565
		566	=head2 VERSION CHECKING
		567
		568	BerkeleyDB comes in various versions, many of them have minor
		569	incompatibilities. This means that traditional "at least version x.x"
		570	checks are often not sufficient.
		571
		572	Example: set the log_autoremove option in a way compatible with <v4.7 and
		573	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		574	bug when the symbol isn't available.
		575
		576	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		577	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
		578
		579	=over 4
		580
		581	=item BDB::VERSION
		582
		583	The C<BDB::VERSION> function, when called without arguments, returns the
		584	Berkeley DB version as a v-string (usually with 3 components). You should
		585	use C<lt> and C<ge> operators exclusively to make comparisons.
		586
		587	Example: check for at least version 4.7.
		588
		589	BDB::VERSION ge v4.7 or die;
		590
		591	=item BDB::VERSION min-version
		592
		593	Returns true if the BDB version is at least the given version (specified
		594	as a v-string), false otherwise.
		595
		596	Example: check for at least version 4.5.
		597
		598	BDB::VERSION v4.7 or die;
		599
		600	=item BDB::VERSION min-version, max-version
		601
		602	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		603	and less then C<max-version>.
		604
		605	Example: check wether version is strictly less then v4.7.
		606
		607	BDB::VERSION v0, v4.7
		608	or die "version 4.7 is not yet supported";
		609
		610	=back
		611
		612	=cut
		613
		614	sub VERSION {
		615	# I was dumb enough to override the VERSION method here, so let's try
		616	# to fix it up.
		617
		618	if ($_[0] eq __PACKAGE__) {
		619	$VERSION
		620	} else {
		621	if (@_ > 0) {
		622	return undef if VERSION_v lt $_[0];
		623	if (@_ > 1) {
		624	return undef if VERSION_v ge $_[1];
		625	}
		626	}
		627
		628	VERSION_v
		629	}
		630	}
		631
172	=head3 CONTROLLING THE NUMBER OF THREADS	632	=head2 CONTROLLING THE NUMBER OF THREADS
173		633
		634	=over 4
		635
174	=item BDB::AIO::min_parallel $nthreads	636	=item BDB::min_parallel $nthreads
175		637
176	Set the minimum number of AIO threads to C<$nthreads>. The current	638	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	639	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	640	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	641	however, is unlimited).
180		642
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	643	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	644	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	645	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.	646	is in the cache and could have been processed faster by a single thread.
185		647
186	It is recommended to keep the number of threads relatively low, as some	648	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	651	versions, 4-32 threads should be fine.
190		652
191	Under most circumstances you don't need to call this function, as the	653	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.	654	module selects a default that is suitable for low to moderate load.
193		655
194	=item BDB::AIO::max_parallel $nthreads	656	=item BDB::max_parallel $nthreads
195		657
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	658	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	659	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	660	them. This function blocks until the limit is reached.
199		661
200	While C<$nthreads> are zero, aio requests get queued but not executed	662	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	663	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	665	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.	666	that all threads are killed and that there are no outstanding requests.
205		667
206	Under normal circumstances you don't need to call this function.	668	Under normal circumstances you don't need to call this function.
207		669
208	=item BDB::AIO::max_idle $nthreads	670	=item BDB::max_idle $nthreads
209		671
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	672	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	673	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	674	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	675	idle, it will free its resources and exit.
…		…
218		680
219	The default is probably ok in most situations, especially if thread	681	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	682	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	683	want to use larger values.
222		684
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	685	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		686
225	This is a very bad function to use in interactive programs because it	687	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	688	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	689	use an C<aio_group> together with a feed callback.
228		690
…		…
236		698
237	You can still queue as many requests as you want. Therefore,	699	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	700	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).	701	as a stop gap to shield against fatal memory overflow (with large values).
240		702
		703	=item $old_cb = BDB::set_sync_prepare $cb
		704
		705	Sets a callback that is called whenever a request is created without an
		706	explicit callback. It has to return two code references. The first is used
		707	as the request callback (it should save the return status), and the second
		708	is called to wait until the first callback has been called (it must set
		709	C<$!> to the return status).
		710
		711	This mechanism can be used to include BDB into other event mechanisms,
		712	such as L<Coro::BDB>.
		713
		714	To allow other, callback-based, events to be executed while callback-less
		715	ones are run, you could use this sync prepare function:
		716
		717	sub {
		718	my $status;
		719	(
		720	sub { $status = $! },
		721	sub { BDB::poll while !defined $status; $! = $status },
		722	)
		723	}
		724
		725	It works by polling for results till the request has finished and then
		726	sets C<$!> to the return value. This means that if you don't use a
		727	callback, BDB would simply fall back to synchronous operations.
		728
		729	By default, or if the sync prepare function is set to C<undef>, is to
		730	execute callback-less BDB requests in the foreground thread, setting C<$!>
		731	to the return value, without polling for other events.
		732
		733	=back
		734
241	=head3 STATISTICAL INFORMATION	735	=head2 STATISTICAL INFORMATION
242		736
		737	=over 4
		738
243	=item BDB::AIO::nreqs	739	=item BDB::nreqs
244		740
245	Returns the number of requests currently in the ready, execute or pending	741	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).	742	states (i.e. for which their callback has not been invoked yet).
247		743
248	Example: wait till there are no outstanding requests anymore:	744	Example: wait till there are no outstanding requests anymore:
249		745
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	746	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	747	while BDB::nreqs;
252		748
253	=item BDB::AIO::nready	749	=item BDB::nready
254		750
255	Returns the number of requests currently in the ready state (not yet	751	Returns the number of requests currently in the ready state (not yet
256	executed).	752	executed).
257		753
258	=item BDB::AIO::npending	754	=item BDB::npending
259		755
260	Returns the number of requests currently in the pending state (executed,	756	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	757	but not yet processed by poll_cb).
262		758
263	=back	759	=back
264		760
265	=cut	761	=cut
266		762
267	# support function to convert a fd into a perl filehandle	763	set_sync_prepare (undef);
268	sub _fd2fh {
269	return undef if $_[0] < 0;
270
271	# try to generate nice filehandles
272	my $sym = "BDB::AIO::fd#$_[0]";
273	local *$sym;
274
275	open *$sym, "+<&=$_[0]" # usually works under any unix
276	or open *$sym, "<&=$_[0]" # cygwin needs this
277	or open *$sym, ">&=$_[0]" # or this
278	or return undef;
279
280	*$sym
281	}
282		764
283	min_parallel 8;	765	min_parallel 8;
284		766
285	END { flush }	767	END { flush }
286		768
287	1;	769	1;
288		770
		771	=head1 COMMON PITFALLS
		772
		773	=head2 Unexpected Crashes
		774
		775	Remember that, by default, BDB will execute requests in parallel, in
		776	somewhat random order. That means that it is easy to run a C<db_get>
		777	request on the same database as a concurrent C<db_close> request, leading
		778	to a crash, silent data corruption, eventually the next world war on
		779	terrorism.
		780
		781	If you only ever use foreground requests (without a callback), this will
		782	not be an issue (unless you use threads).
		783
		784	=head2 Unexpected Freezes or Deadlocks
		785
		786	Remember that, by default, BDB will execute requests in parallel, which
		787	easily leads to deadlocks (even concurrent put's on the same database can
		788	deadlock).
		789
		790	You either need to run deadlock detection (and handle the resulting
		791	errors), or make sure only one process ever updates the database, ine one
		792	thread, e.g. by using only foreground requests (without a callback).
		793
289	=head2 FORK BEHAVIOUR	794	=head1 FORK BEHAVIOUR
290		795
291	This module should do "the right thing" when the process using it forks:	796	This module should do "the right thing" when the process using it forks:
292		797
293	Before the fork, IO::AIO enters a quiescent state where no requests	798	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	799	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	800	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	801	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	802	(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	803	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	804	parent process has been reached again.
300		805
301	In short: the parent will, after a short pause, continue as if fork had	806	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	807	not been called, while the child will act as if BDB has not been used
303	yet.	808	yet.
304		809
		810	Win32 note: there is no fork on win32, and perls emulation of it is too
		811	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		812	yet, switch to a more capable platform.
		813
305	=head2 MEMORY USAGE	814	=head1 MEMORY USAGE
306		815
307	Per-request usage:	816	Per-request usage:
308		817
309	Each aio request uses - depending on your architecture - around 100-200	818	Each aio request uses - depending on your architecture - around 100-200
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	819	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	820	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	821	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.	822	will consume memory till the request has entered the done state.
314		823
315	This is now awfully much, so queuing lots of requests is not usually a	824	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	825	problem.
317		826
318	Per-thread usage:	827	Per-thread usage:
319		828
320	In the execution phase, some aio requests require more memory for	829	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	830	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	831	structures (usually around 16k-128k, depending on the OS).
323		832
		833	=head1 WIN32 FILENAMES/DATABASE NAME MESS
		834
		835	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		836	an internal flag to store wether a filename is Unicode or ANSI, but that
		837	flag is used for somethign else in the perl core, so there is no way to
		838	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		839	tries to work around this issue by assuming that the filename is an ANSI
		840	filename and BDB was built for unicode support.
		841
324	=head1 KNOWN BUGS	842	=head1 KNOWN BUGS
325		843
326	Known bugs will be fixed in the next release.	844	Known bugs will be fixed in the next release, except:
		845
		846	If you use a transaction in any request, and the request returns
		847	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		848	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		849	above.
327		850
328	=head1 SEE ALSO	851	=head1 SEE ALSO
329		852
330	L<Coro::AIO>.	853	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		854	syntax), L<IO::AIO> (nice to have).
331		855
332	=head1 AUTHOR	856	=head1 AUTHOR
333		857
334	Marc Lehmann <schmorp@schmorp.de>	858	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	859	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 1.67 by root, Tue Feb 2 04:07:06 2016 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 1.67 by root, Tue Feb 2 04:07:06 2016 UTC