[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 1.20 by root, Fri Dec 7 13:14:41 2007 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	BDB::AIO - Asynchronous Berkeley DB access	3	BDB - Asynchronous Berkeley DB access
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB::AIO;	7	use BDB;
		8
		9	my $env = db_env_create;
		10
		11	mkdir "bdtest", 0700;
		12	db_env_open
		13	$env,
		14	"bdtest",
		15	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL
		16	\| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		17	0600;
		18
		19	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		20
		21	my $db = db_create $env;
		22	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE
		23	\| BDB::READ_UNCOMMITTED, 0600;
		24	db_put $db, undef, "key", "data", 0, sub {
		25	db_del $db, undef, "key";
		26	};
		27	db_sync $db;
		28
		29	# automatic result processing with AnyEvent:
		30	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		31	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		32
		33	# automatic result processing with EV:
		34	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		35
		36	# with Glib:
		37	add_watch Glib::IO BDB::poll_fileno,
		38	in => sub { BDB::poll_cb; 1 };
		39
		40	# or simply flush manually
		41	BDB::flush;
		42
8		43
9	=head1 DESCRIPTION	44	=head1 DESCRIPTION
10		45
11	=head2 EXAMPLE	46	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
		47	The BDB API is very similar to the C API (the translation has been very faithful).
		48
		49	See also the example sections in the document below and possibly the eg/
		50	subdirectory of the BDB distribution. Last not least see the IO::AIO
		51	documentation, as that module uses almost the same asynchronous request
		52	model as this module.
		53
		54	I know this is woefully inadequate documentation. Send a patch!
		55
12		56
13	=head1 REQUEST ANATOMY AND LIFETIME	57	=head1 REQUEST ANATOMY AND LIFETIME
14		58
15	Every request method creates a request. which is a C data structure not	59	Every request method creates a request. which is a C data structure not
16	directly visible to Perl.	60	directly visible to Perl.
55		99
56	=back	100	=back
57		101
58	=cut	102	=cut
59		103
60	package BDB::AIO;	104	package BDB;
61		105
62	no warnings;	106	no warnings;
63	use strict 'vars';	107	use strict 'vars';
64		108
65	use base 'Exporter';	109	use base 'Exporter';
66		110
67	BEGIN {	111	BEGIN {
68	our $VERSION = '0.1';	112	our $VERSION = '1.2';
69		113
70	our @BDB_REQ = qw();	114	our @BDB_REQ = qw(
		115	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
		116	db_env_memp_sync db_env_memp_trickle
		117	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
		118	db_txn_commit db_txn_abort db_txn_finish
		119	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
		120	db_sequence_open db_sequence_close
		121	db_sequence_get db_sequence_remove
		122	);
		123	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
		124	our @EXPORT_OK = qw(
71	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	125	poll_fileno poll_cb poll_wait flush
72	min_parallel max_parallel max_idle	126	min_parallel max_parallel max_idle
73	nreqs nready npending nthreads	127	nreqs nready npending nthreads
74	max_poll_time max_poll_reqs);	128	max_poll_time max_poll_reqs
		129	);
75		130
76	require XSLoader;	131	require XSLoader;
77	XSLoader::load ("BDB::AIO", $VERSION);	132	XSLoader::load ("BDB", $VERSION);
78	}	133	}
79		134
		135	=head2 BERKELEYDB FUNCTIONS
		136
		137	All of these are functions. The create functions simply return a new
		138	object and never block. All the remaining functions all take an optional
		139	callback as last argument. If it is missing, then the fucntion will be
		140	executed synchronously.
		141
		142	BDB functions that cannot block (mostly functions that manipulate
		143	settings) are method calls on the relevant objects, so the rule of thumb
		144	is: if its a method, its not blocking, if its a function, it takes a
		145	callback as last argument.
		146
		147	In the following, C<$int> signifies an integer return value,
		148	C<octetstring> is a "binary string" (i.e. a perl string with no character
		149	indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
		150	integer, C<NV> is a floating point value.
		151
		152	The C<SV *> types are generic perl scalars (for input and output of data
		153	values), and the C<SV *callback> is the optional callback function to call
		154	when the request is completed.
		155
		156	The various C<DB_ENV> etc. arguments are handles return by
		157	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		158	appended C<_ornull> this means they are optional and you can pass C<undef>
		159	for them, resulting a NULL pointer on the C level.
		160
		161	=head3 BDB functions
		162
		163	Functions in the BDB namespace, exported by default:
		164
		165	$env = db_env_create (U32 env_flags = 0)
		166	flags: RPCCLIENT
		167
		168	db_env_open (DB_ENV env, octetstring db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		169	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
		170	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		171	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		172	flags: FORCE
		173	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		174	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		175	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		176	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		177
		178	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		179	flags: XA_CREATE
		180
		181	db_open (DB db, DB_TXN_ornull txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		182	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		183	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		184	flags: DB_NOSYNC
		185	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)
		186	flags: FREELIST_ONLY FREE_SPACE
		187	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		188	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		189	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		190	flags: APPEND NODUPDATA NOOVERWRITE
		191	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		192	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		193	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		194	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		195	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		196	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		197	flags: TXN_NOSYNC TXN_SYNC
		198	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		199
		200	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		201	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		202	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		203	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		204	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		205	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
		206	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		207	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		208
		209	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		210	flags: CREATE EXCL
		211	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		212	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)
		213	flags: TXN_NOSYNC
		214	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		215	flags: TXN_NOSYNC
		216
		217	=head4 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		218
		219	This is not actually a Berkeley DB function but a BDB module
		220	extension. The background for this exytension is: It is very annoying to
		221	have to check every single BDB function for error returns and provide a
		222	codepath out of your transaction. While the BDB module still makes this
		223	possible, it contains the following extensions:
		224
		225	When a transaction-protected function returns any operating system
		226	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		227	transaction. This flag is also set by Berkeley DB functions themselves
		228	when an operation fails with LOCK_DEADLOCK, and it causes all further
		229	operations on that transaction (including C<db_txn_commit>) to fail.
		230
		231	The C<db_txn_finish> request will look at this flag, and, if it is set,
		232	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		233	if it isn't set to something else yet). If it isn't set, it will call
		234	C<db_txn_commit> and return the error normally.
		235
		236	How to use this? Easy: just write your transaction normally:
		237
		238	my $txn = $db_env->txn_begin;
		239	db_get $db, $txn, "key", my $data;
		240	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		241	db_txn_finish $txn;
		242	die "transaction failed" if $!;
		243
		244	That is, handle only the expected errors. If something unexpected happens
		245	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		246	requests (db_put in this case) will simply be skipped (they will fail with
		247	LOCK_DEADLOCK) and the transaction will be aborted.
		248
		249	You can use the C<< $txn->failed >> method to check wether a transaction
		250	has failed in this way and abort further processing (excluding
		251	C<db_txn_finish>).
		252
		253	=head3 DB_ENV/database environment methods
		254
		255	Methods available on DB_ENV/$env handles:
		256
		257	DESTROY (DB_ENV_ornull *env)
		258	CODE:
		259	if (env)
		260	env->close (env, 0);
		261
		262	$int = $env->set_data_dir (const char *dir)
		263	$int = $env->set_tmp_dir (const char *dir)
		264	$int = $env->set_lg_dir (const char *dir)
		265	$int = $env->set_shm_key (long shm_key)
		266	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		267	$int = $env->set_flags (U32 flags, int onoff)
		268	$env->set_errfile (FILE *errfile = 0)
		269	$env->set_msgfile (FILE *msgfile = 0)
		270	$int = $env->set_verbose (U32 which, int onoff = 1)
		271	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		272	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		273	$int = $env->set_mp_max_openfd (int maxopenfd);
		274	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		275	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		276	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		277	$int = $env->set_lk_max_lockers (U32 max)
		278	$int = $env->set_lk_max_locks (U32 max)
		279	$int = $env->set_lk_max_objects (U32 max)
		280	$int = $env->set_lg_bsize (U32 max)
		281	$int = $env->set_lg_max (U32 max)
		282	$int = $env->mutex_set_increment (U32 increment)
		283	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		284	$int = $env->mutex_set_max (U32 max)
		285	$int = $env->mutex_set_align (U32 align)
		286
		287	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		288	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		289
		290	=head4 Example:
		291
		292	use AnyEvent;
		293	use BDB;
		294
		295	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		296	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		297
		298	BDB::min_parallel 8;
		299
		300	my $env = db_env_create;
		301
		302	mkdir "bdtest", 0700;
		303	db_env_open
		304	$env,
		305	"bdtest",
		306	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		307	0600;
		308
		309	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		310
		311
		312	=head3 DB/database methods
		313
		314	Methods available on DB/$db handles:
		315
		316	DESTROY (DB_ornull *db)
		317	CODE:
		318	if (db)
		319	{
		320	SV env = (SV )db->app_private;
		321	db->close (db, 0);
		322	SvREFCNT_dec (env);
		323	}
		324
		325	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		326	$int = $db->set_flags (U32 flags)
		327	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		328	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		329	Hash: DUP DUPSORT
		330	Queue: INORDER
		331	Recno: RENUMBER SNAPSHOT
		332
		333	$int = $db->set_encrypt (const char *password, U32 flags)
		334	$int = $db->set_lorder (int lorder)
		335	$int = $db->set_bt_minkey (U32 minkey)
		336	$int = $db->set_re_delim (int delim)
		337	$int = $db->set_re_pad (int re_pad)
		338	$int = $db->set_re_source (char *source)
		339	$int = $db->set_re_len (U32 re_len)
		340	$int = $db->set_h_ffactor (U32 h_ffactor)
		341	$int = $db->set_h_nelem (U32 h_nelem)
		342	$int = $db->set_q_extentsize (U32 extentsize)
		343
		344	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		345	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		346	$seq = $db->sequence (U32 flags = 0)
		347
		348	=head4 Example:
		349
		350	my $db = db_create $env;
		351	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		352
		353	for (1..1000) {
		354	db_put $db, undef, "key $_", "data $_";
		355
		356	db_key_range $db, undef, "key $_", my $keyrange;
		357	my ($lt, $eq, $gt) = @$keyrange;
		358	}
		359
		360	db_del $db, undef, "key $_" for 1..1000;
		361
		362	db_sync $db;
		363
		364
		365	=head3 DB_TXN/transaction methods
		366
		367	Methods available on DB_TXN/$txn handles:
		368
		369	DESTROY (DB_TXN_ornull *txn)
		370	CODE:
		371	if (txn)
		372	txn->abort (txn);
		373
		374	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		375	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		376
		377	$bool = $txn->failed
		378	# see db_txn_finish documentation, above
		379
		380
		381	=head3 DBC/cursor methods
		382
		383	Methods available on DBC/$dbc handles:
		384
		385	DESTROY (DBC_ornull *dbc)
		386	CODE:
		387	if (dbc)
		388	dbc->c_close (dbc);
		389
		390	=head4 Example:
		391
		392	my $c = $db->cursor;
		393
		394	for (;;) {
		395	db_c_get $c, my $key, my $data, BDB::NEXT;
		396	warn "<$!,$key,$data>";
		397	last if $!;
		398	}
		399
		400	db_c_close $c;
		401
		402
		403	=head3 DB_SEQUENCE/sequence methods
		404
		405	Methods available on DB_SEQUENCE/$seq handles:
		406
		407	DESTROY (DB_SEQUENCE_ornull *seq)
		408	CODE:
		409	if (seq)
		410	seq->close (seq, 0);
		411
		412	$int = $seq->initial_value (db_seq_t value)
		413	$int = $seq->set_cachesize (U32 size)
		414	$int = $seq->set_flags (U32 flags)
		415	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		416	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		417
		418	=head4 Example:
		419
		420	my $seq = $db->sequence;
		421
		422	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		423	db_sequence_get $seq, undef, 1, my $value;
		424
		425
80	=head2 SUPPORT FUNCTIONS	426	=head2 SUPPORT FUNCTIONS
81		427
82	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	428	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
83		429
84	=over 4	430	=over 4
85		431
86	=item $fileno = BDB::AIO::poll_fileno	432	=item $fileno = BDB::poll_fileno
87		433
88	Return the I<request result pipe file descriptor>. This filehandle must be	434	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	435	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	436	select, see below or the SYNOPSIS). If the pipe becomes readable you have
91	to call C<poll_cb> to check the results.	437	to call C<poll_cb> to check the results.
92		438
93	See C<poll_cb> for an example.	439	See C<poll_cb> for an example.
94		440
95	=item BDB::AIO::poll_cb	441	=item BDB::poll_cb
96		442
97	Process some outstanding events on the result pipe. You have to call this	443	Process some outstanding events on the result pipe. You have to call this
98	regularly. Returns the number of events processed. Returns immediately	444	regularly. Returns the number of events processed. Returns immediately
99	when no events are outstanding. The amount of events processed depends on	445	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>.	446	the settings of C<BDB::max_poll_req> and C<BDB::max_poll_time>.
101		447
102	If not all requests were processed for whatever reason, the filehandle	448	If not all requests were processed for whatever reason, the filehandle
103	will still be ready when C<poll_cb> returns.	449	will still be ready when C<poll_cb> returns.
104		450
105	Example: Install an Event watcher that automatically calls	451	Example: Install an Event watcher that automatically calls
106	BDB::AIO::poll_cb with high priority:	452	BDB::poll_cb with high priority:
107		453
108	Event->io (fd => BDB::AIO::poll_fileno,	454	Event->io (fd => BDB::poll_fileno,
109	poll => 'r', async => 1,	455	poll => 'r', async => 1,
110	cb => \&BDB::AIO::poll_cb);	456	cb => \&BDB::poll_cb);
111		457
112	=item BDB::AIO::max_poll_reqs $nreqs	458	=item BDB::max_poll_reqs $nreqs
113		459
114	=item BDB::AIO::max_poll_time $seconds	460	=item BDB::max_poll_time $seconds
115		461
116	These set the maximum number of requests (default C<0>, meaning infinity)	462	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	463	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	464	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	465	C<BDB::poll_cb> to process requests (more correctly the mininum amount
120	of time C<poll_cb> is allowed to use).	466	of time C<poll_cb> is allowed to use).
121		467
122	Setting C<max_poll_time> to a non-zero value creates an overhead of one	468	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	469	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	470	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	474	interactiveness when perl is not fast enough to process all requests in
129	time.	475	time.
130		476
131	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	477	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
132		478
133	Example: Install an Event watcher that automatically calls	479	Example: Install an EV watcher that automatically calls
134	BDB::AIO::poll_cb with low priority, to ensure that other parts of the	480	BDB::poll_cb with low priority, to ensure that other parts of the
135	program get the CPU sometimes even under high AIO load.	481	program get the CPU sometimes even under high load.
136		482
137	# try not to spend much more than 0.1s in poll_cb	483	# try not to spend much more than 0.1s in poll_cb
138	BDB::AIO::max_poll_time 0.1;	484	BDB::max_poll_time 0.1;
139		485
140	# use a low priority so other tasks have priority	486	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		487
145	=item BDB::AIO::poll_wait	488	=item BDB::poll_wait
146		489
147	If there are any outstanding requests and none of them in the result	490	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	491	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	492	does a C<select> on the filehandle. This is useful if you want to
150	synchronously wait for some requests to finish).	493	synchronously wait for some requests to finish).
151		494
152	See C<nreqs> for an example.	495	See C<nreqs> for an example.
153		496
154	=item BDB::AIO::poll	497	=item BDB::poll
155		498
156	Waits until some requests have been handled.	499	Waits until some requests have been handled.
157		500
158	Returns the number of requests processed, but is otherwise strictly	501	Returns the number of requests processed, but is otherwise strictly
159	equivalent to:	502	equivalent to:
160		503
161	BDB::AIO::poll_wait, BDB::AIO::poll_cb	504	BDB::poll_wait, BDB::poll_cb
162		505
163	=item BDB::AIO::flush	506	=item BDB::flush
164		507
165	Wait till all outstanding AIO requests have been handled.	508	Wait till all outstanding BDB requests have been handled.
166		509
167	Strictly equivalent to:	510	Strictly equivalent to:
168		511
169	BDB::AIO::poll_wait, BDB::AIO::poll_cb	512	BDB::poll_wait, BDB::poll_cb
170	while BDB::AIO::nreqs;	513	while BDB::nreqs;
		514
		515	=back
171		516
172	=head3 CONTROLLING THE NUMBER OF THREADS	517	=head3 CONTROLLING THE NUMBER OF THREADS
173		518
		519	=over 4
		520
174	=item BDB::AIO::min_parallel $nthreads	521	=item BDB::min_parallel $nthreads
175		522
176	Set the minimum number of AIO threads to C<$nthreads>. The current	523	Set the minimum number of BDB threads to C<$nthreads>. The current
177	default is C<8>, which means eight asynchronous operations can execute	524	default is C<8>, which means eight asynchronous operations can execute
178	concurrently at any one time (the number of outstanding requests,	525	concurrently at any one time (the number of outstanding requests,
179	however, is unlimited).	526	however, is unlimited).
180		527
181	BDB::AIO starts threads only on demand, when an AIO request is queued and	528	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	529	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	530	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.	531	is in the cache and could have been processed faster by a single thread.
185		532
186	It is recommended to keep the number of threads relatively low, as some	533	It is recommended to keep the number of threads relatively low, as some
…		…
189	versions, 4-32 threads should be fine.	536	versions, 4-32 threads should be fine.
190		537
191	Under most circumstances you don't need to call this function, as the	538	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.	539	module selects a default that is suitable for low to moderate load.
193		540
194	=item BDB::AIO::max_parallel $nthreads	541	=item BDB::max_parallel $nthreads
195		542
196	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	543	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
197	specified number of threads are currently running, this function kills	544	specified number of threads are currently running, this function kills
198	them. This function blocks until the limit is reached.	545	them. This function blocks until the limit is reached.
199		546
200	While C<$nthreads> are zero, aio requests get queued but not executed	547	While C<$nthreads> are zero, aio requests get queued but not executed
201	until the number of threads has been increased again.	548	until the number of threads has been increased again.
…		…
203	This module automatically runs C<max_parallel 0> at program end, to ensure	550	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.	551	that all threads are killed and that there are no outstanding requests.
205		552
206	Under normal circumstances you don't need to call this function.	553	Under normal circumstances you don't need to call this function.
207		554
208	=item BDB::AIO::max_idle $nthreads	555	=item BDB::max_idle $nthreads
209		556
210	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	557	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
211	threads that did not get a request to process within 10 seconds). That	558	threads that did not get a request to process within 10 seconds). That
212	means if a thread becomes idle while C<$nthreads> other threads are also	559	means if a thread becomes idle while C<$nthreads> other threads are also
213	idle, it will free its resources and exit.	560	idle, it will free its resources and exit.
…		…
218		565
219	The default is probably ok in most situations, especially if thread	566	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	567	creation is fast. If thread creation is very slow on your system you might
221	want to use larger values.	568	want to use larger values.
222		569
223	=item $oldmaxreqs = BDB::AIO::max_outstanding $maxreqs	570	=item $oldmaxreqs = BDB::max_outstanding $maxreqs
224		571
225	This is a very bad function to use in interactive programs because it	572	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	573	blocks, and a bad way to reduce concurrency because it is inexact: Better
227	use an C<aio_group> together with a feed callback.	574	use an C<aio_group> together with a feed callback.
228		575
…		…
236		583
237	You can still queue as many requests as you want. Therefore,	584	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	585	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).	586	as a stop gap to shield against fatal memory overflow (with large values).
240		587
		588	=item BDB::set_sync_prepare $cb
		589
		590	Sets a callback that is called whenever a request is created without an
		591	explicit callback. It has to return two code references. The first is used
		592	as the request callback, and the second is called to wait until the first
		593	callback has been called. The default implementation works like this:
		594
		595	sub {
		596	my $status;
		597	(
		598	sub { $status = $! },
		599	sub { BDB::poll while !defined $status; $! = $status },
		600	)
		601	}
		602
		603	=back
		604
241	=head3 STATISTICAL INFORMATION	605	=head3 STATISTICAL INFORMATION
242		606
		607	=over 4
		608
243	=item BDB::AIO::nreqs	609	=item BDB::nreqs
244		610
245	Returns the number of requests currently in the ready, execute or pending	611	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).	612	states (i.e. for which their callback has not been invoked yet).
247		613
248	Example: wait till there are no outstanding requests anymore:	614	Example: wait till there are no outstanding requests anymore:
249		615
250	BDB::AIO::poll_wait, BDB::AIO::poll_cb	616	BDB::poll_wait, BDB::poll_cb
251	while BDB::AIO::nreqs;	617	while BDB::nreqs;
252		618
253	=item BDB::AIO::nready	619	=item BDB::nready
254		620
255	Returns the number of requests currently in the ready state (not yet	621	Returns the number of requests currently in the ready state (not yet
256	executed).	622	executed).
257		623
258	=item BDB::AIO::npending	624	=item BDB::npending
259		625
260	Returns the number of requests currently in the pending state (executed,	626	Returns the number of requests currently in the pending state (executed,
261	but not yet processed by poll_cb).	627	but not yet processed by poll_cb).
262		628
263	=back	629	=back
264		630
265	=cut	631	=cut
266		632
267	# support function to convert a fd into a perl filehandle	633	set_sync_prepare {
268	sub _fd2fh {	634	my $status;
269	return undef if $_[0] < 0;	635	(
270		636	sub {
271	# try to generate nice filehandles	637	$status = $!;
272	my $sym = "BDB::AIO::fd#$_[0]";	638	},
273	local *$sym;	639	sub {
274		640	BDB::poll while !defined $status;
275	open *$sym, "+<&=$_[0]" # usually works under any unix	641	$! = $status;
276	or open *$sym, "<&=$_[0]" # cygwin needs this	642	},
277	or open *$sym, ">&=$_[0]" # or this	643	)
278	or return undef;	644	};
279
280	*$sym
281	}
282		645
283	min_parallel 8;	646	min_parallel 8;
284		647
285	END { flush }	648	END { flush }
286		649
…		…
288		651
289	=head2 FORK BEHAVIOUR	652	=head2 FORK BEHAVIOUR
290		653
291	This module should do "the right thing" when the process using it forks:	654	This module should do "the right thing" when the process using it forks:
292		655
293	Before the fork, IO::AIO enters a quiescent state where no requests	656	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	657	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	658	the fork the parent simply leaves the quiescent state and continues
296	request/result processing, while the child frees the request/result queue	659	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	660	(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	661	parent). Threads will be started on demand until the limit set in the
299	parent process has been reached again.	662	parent process has been reached again.
300		663
301	In short: the parent will, after a short pause, continue as if fork had	664	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	665	not been called, while the child will act as if BDB has not been used
303	yet.	666	yet.
304		667
305	=head2 MEMORY USAGE	668	=head2 MEMORY USAGE
306		669
307	Per-request usage:	670	Per-request usage:
…		…
310	bytes of memory. In addition, stat requests need a stat buffer (possibly	673	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	674	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	675	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.	676	will consume memory till the request has entered the done state.
314		677
315	This is now awfully much, so queuing lots of requests is not usually a	678	This is not awfully much, so queuing lots of requests is not usually a
316	problem.	679	problem.
317		680
318	Per-thread usage:	681	Per-thread usage:
319		682
320	In the execution phase, some aio requests require more memory for	683	In the execution phase, some aio requests require more memory for
321	temporary buffers, and each thread requires a stack and other data	684	temporary buffers, and each thread requires a stack and other data
322	structures (usually around 16k-128k, depending on the OS).	685	structures (usually around 16k-128k, depending on the OS).
323		686
324	=head1 KNOWN BUGS	687	=head1 KNOWN BUGS
325		688
326	Known bugs will be fixed in the next release.	689	Known bugs will be fixed in the next release, except:
		690
		691	If you use a transaction in any request, and the request returns
		692	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		693	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		694	above.
327		695
328	=head1 SEE ALSO	696	=head1 SEE ALSO
329		697
330	L<Coro::AIO>.	698	L<Coro::BDB>, L<IO::AIO>.
331		699
332	=head1 AUTHOR	700	=head1 AUTHOR
333		701
334	Marc Lehmann <schmorp@schmorp.de>	702	Marc Lehmann <schmorp@schmorp.de>
335	http://home.schmorp.de/	703	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 1.20 by root, Fri Dec 7 13:14:41 2007 UTC

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Revision 1.1 by root, Mon Feb 5 18:40:55 2007 UTC vs.
Revision 1.20 by root, Fri Dec 7 13:14:41 2007 UTC