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Comparing BDB/BDB.pm (file contents):
Revision 1.13 by root, Mon Aug 13 12:07:55 2007 UTC vs.
Revision 1.20 by root, Fri Dec 7 13:14:41 2007 UTC

… …
3BDB - Asynchronous Berkeley DB access 3BDB - Asynchronous Berkeley DB access
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use BDB; 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
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 46See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12The BDB API is very similar to the C API (the translation has been very faithful). 47The BDB API is very similar to the C API (the translation has been very faithful).
… …
72use strict 'vars'; 107use strict 'vars';
73 108
74use base 'Exporter'; 109use base 'Exporter';
75 110
76BEGIN { 111BEGIN {
77 our $VERSION = '1.0'; 112 our $VERSION = '1.2';
78 113
79 our @BDB_REQ = qw( 114 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 115 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 116 db_env_memp_sync db_env_memp_trickle
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 117 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 118 db_txn_commit db_txn_abort db_txn_finish
84 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del 119 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
85 db_sequence_open db_sequence_close 120 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 121 db_sequence_get db_sequence_remove
87 ); 122 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 123 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
126=head3 BDB functions 161=head3 BDB functions
127 162
128Functions in the BDB namespace, exported by default: 163Functions in the BDB namespace, exported by default:
129 164
130 $env = db_env_create (U32 env_flags = 0) 165 $env = db_env_create (U32 env_flags = 0)
166 flags: RPCCLIENT
131 167
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 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
133 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef) 170 db_env_close (DB_ENV *env, U32 flags = 0, SV *callback = &PL_sv_undef)
134 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, 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
135 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef) 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
136 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) 175 db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef)
137 db_env_memp_trickle (DB_ENV *env, int percent, 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)
138 177
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 178 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
179 flags: XA_CREATE
140 180
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 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
142 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 183 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
184 flags: DB_NOSYNC
143 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) 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
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 187 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
145 db_key_range (DB *db, DB_TXN_ornull *txn, SV *key, SV *key_range, 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)
146 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, 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
147 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 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
148 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 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
149 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 195 db_del (DB *db, DB_TXN_ornull *txn, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
150 db_txn_commit (DB_TXN *txn, 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
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 198 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
199
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 200 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef)
153 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef) 201 db_c_count (DBC *dbc, SV *count, U32 flags = 0, SV *callback = &PL_sv_undef)
154 db_c_put (DBC *dbc, SV *key, SV *data, 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
155 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 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
156 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef) 206 db_c_pget (DBC *dbc, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
157 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef) 207 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 208
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 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
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 211 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef)
161 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) 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
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 214 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
215 flags: TXN_NOSYNC
163 216
217=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
218
219This is not actually a Berkeley DB function but a BDB module
220extension. The background for this exytension is: It is very annoying to
221have to check every single BDB function for error returns and provide a
222codepath out of your transaction. While the BDB module still makes this
223possible, it contains the following extensions:
224
225When a transaction-protected function returns any operating system
226error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
227transaction. This flag is also set by Berkeley DB functions themselves
228when an operation fails with LOCK_DEADLOCK, and it causes all further
229operations on that transaction (including C<db_txn_commit>) to fail.
230
231The C<db_txn_finish> request will look at this flag, and, if it is set,
232will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
233if it isn't set to something else yet). If it isn't set, it will call
234C<db_txn_commit> and return the error normally.
235
236How 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
244That 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
246requests (db_put in this case) will simply be skipped (they will fail with
247LOCK_DEADLOCK) and the transaction will be aborted.
248
249You can use the C<< $txn->failed >> method to check wether a transaction
250has failed in this way and abort further processing (excluding
251C<db_txn_finish>).
164 252
165=head3 DB_ENV/database environment methods 253=head3 DB_ENV/database environment methods
166 254
167Methods available on DB_ENV/$env handles: 255Methods available on DB_ENV/$env handles:
168 256
… …
179 $int = $env->set_flags (U32 flags, int onoff) 267 $int = $env->set_flags (U32 flags, int onoff)
180 $env->set_errfile (FILE *errfile = 0) 268 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 269 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 270 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 271 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 272 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 273 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 274 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 275 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 276 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 277 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 278 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 279 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 280 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (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)
194 286
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 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
196 289
197=head4 Example: 290=head4 Example:
198 291
199 use AnyEvent; 292 use AnyEvent;
200 use BDB; 293 use BDB;
… …
229 SvREFCNT_dec (env); 322 SvREFCNT_dec (env);
230 } 323 }
231 324
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 325 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 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
234 $int = $db->set_encrypt (const char *password, U32 flags) 333 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 334 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 335 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 336 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 337 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 340 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 341 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 342 $int = $db->set_q_extentsize (U32 extentsize)
244 343
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 344 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
345 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 346 $seq = $db->sequence (U32 flags = 0)
247 347
248=head4 Example: 348=head4 Example:
249 349
250 my $db = db_create $env; 350 my $db = db_create $env;
… …
269 DESTROY (DB_TXN_ornull *txn) 369 DESTROY (DB_TXN_ornull *txn)
270 CODE: 370 CODE:
271 if (txn) 371 if (txn)
272 txn->abort (txn); 372 txn->abort (txn);
273 373
274 $int = $txn->set_timeout (NV timeout, U32 flags) 374 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
375 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
376
377 $bool = $txn->failed
378 # see db_txn_finish documentation, above
275 379
276 380
277=head3 DBC/cursor methods 381=head3 DBC/cursor methods
278 382
279Methods available on DBC/$dbc handles: 383Methods available on DBC/$dbc handles:
… …
306 seq->close (seq, 0); 410 seq->close (seq, 0);
307 411
308 $int = $seq->initial_value (db_seq_t value) 412 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 413 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 414 $int = $seq->set_flags (U32 flags)
415 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 416 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 417
313=head4 Example: 418=head4 Example:
314 419
315 my $seq = $db->sequence; 420 my $seq = $db->sequence;
… …
369interactiveness when perl is not fast enough to process all requests in 474interactiveness when perl is not fast enough to process all requests in
370time. 475time.
371 476
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 477For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 478
374Example: Install an Event watcher that automatically calls 479Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 480BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 481program get the CPU sometimes even under high load.
377 482
378 # 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
379 BDB::max_poll_time 0.1; 484 BDB::max_poll_time 0.1;
380 485
381 # use a low priority so other tasks have priority 486 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
382 Event->io (fd => BDB::poll_fileno,
383 poll => 'r', nice => 1,
384 cb => &BDB::poll_cb);
385 487
386=item BDB::poll_wait 488=item BDB::poll_wait
387 489
388If there are any outstanding requests and none of them in the result 490If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 491phase, wait till the result filehandle becomes ready for reading (simply
… …
401 503
402 BDB::poll_wait, BDB::poll_cb 504 BDB::poll_wait, BDB::poll_cb
403 505
404=item BDB::flush 506=item BDB::flush
405 507
406Wait till all outstanding AIO requests have been handled. 508Wait till all outstanding BDB requests have been handled.
407 509
408Strictly equivalent to: 510Strictly equivalent to:
409 511
410 BDB::poll_wait, BDB::poll_cb 512 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 513 while BDB::nreqs;
… …
416 518
417=over 4 519=over 4
418 520
419=item BDB::min_parallel $nthreads 521=item BDB::min_parallel $nthreads
420 522
421Set the minimum number of AIO threads to C<$nthreads>. The current 523Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 524default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 525concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 526however, is unlimited).
425 527
426BDB starts threads only on demand, when an AIO request is queued and 528BDB starts threads only on demand, when an BDB request is queued and
427no free thread exists. Please note that queueing up a hundred requests can 529no free thread exists. Please note that queueing up a hundred requests can
428create demand for a hundred threads, even if it turns out that everything 530create demand for a hundred threads, even if it turns out that everything
429is in the cache and could have been processed faster by a single thread. 531is in the cache and could have been processed faster by a single thread.
430 532
431It is recommended to keep the number of threads relatively low, as some 533It is recommended to keep the number of threads relatively low, as some
… …
436Under most circumstances you don't need to call this function, as the 538Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 539module selects a default that is suitable for low to moderate load.
438 540
439=item BDB::max_parallel $nthreads 541=item BDB::max_parallel $nthreads
440 542
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 543Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 544specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 545them. This function blocks until the limit is reached.
444 546
445While C<$nthreads> are zero, aio requests get queued but not executed 547While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 548until the number of threads has been increased again.
… …
549 651
550=head2 FORK BEHAVIOUR 652=head2 FORK BEHAVIOUR
551 653
552This module should do "the right thing" when the process using it forks: 654This module should do "the right thing" when the process using it forks:
553 655
554Before the fork, IO::AIO enters a quiescent state where no requests 656Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 657can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 658the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 659request/result processing, while the child frees the request/result queue
558(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
559parent). Threads will be started on demand until the limit set in the 661parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 662parent process has been reached again.
561 663
562In short: the parent will, after a short pause, continue as if fork had 664In short: the parent will, after a short pause, continue as if fork had
563not been called, while the child will act as if IO::AIO has not been used 665not been called, while the child will act as if BDB has not been used
564yet. 666yet.
565 667
566=head2 MEMORY USAGE 668=head2 MEMORY USAGE
567 669
568Per-request usage: 670Per-request usage:
… …
582temporary buffers, and each thread requires a stack and other data 684temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 685structures (usually around 16k-128k, depending on the OS).
584 686
585=head1 KNOWN BUGS 687=head1 KNOWN BUGS
586 688
587Known bugs will be fixed in the next release. 689Known 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.
588 695
589=head1 SEE ALSO 696=head1 SEE ALSO
590 697
591L<Coro::AIO>. 698L<Coro::BDB>, L<IO::AIO>.
592 699
593=head1 AUTHOR 700=head1 AUTHOR
594 701
595 Marc Lehmann <schmorp@schmorp.de> 702 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 703 http://home.schmorp.de/

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