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Comparing BDB/BDB.pm (file contents):
Revision 1.11 by root, Mon Aug 13 12:04:41 2007 UTC vs.
Revision 1.19 by root, Wed Dec 5 13:01:46 2007 UTC

… …
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use BDB; 7 use BDB;
8 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
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 ahs been very faithful). 47The BDB API is very similar to the C API (the translation has been very faithful).
13 48
14See also the example sections in the document below and possibly the eg/ 49See also the example sections in the document below and possibly the eg/
15subdirectory of the BDB distribution. Last not least see the IO::AIO 50subdirectory of the BDB distribution. Last not least see the IO::AIO
16documentation, as that module uses almost the same asynchronous request 51documentation, as that module uses almost the same asynchronous request
17model as this module. 52model as this module.
… …
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_unde 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)
… …
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)
194 282
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 283 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
284 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
196 285
197=head4 example 286=head4 Example:
198 287
199 use AnyEvent; 288 use AnyEvent;
200 use BDB; 289 use BDB;
201 290
202 our $FH; open $FH, "<&=" . BDB::poll_fileno; 291 our $FH; open $FH, "<&=" . BDB::poll_fileno;
… …
229 SvREFCNT_dec (env); 318 SvREFCNT_dec (env);
230 } 319 }
231 320
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 321 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 322 $int = $db->set_flags (U32 flags)
323 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
324 Btree: DUP DUPSORT RECNUM REVSPLITOFF
325 Hash: DUP DUPSORT
326 Queue: INORDER
327 Recno: RENUMBER SNAPSHOT
328
234 $int = $db->set_encrypt (const char *password, U32 flags) 329 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 330 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 331 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 332 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 333 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 336 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 337 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 338 $int = $db->set_q_extentsize (U32 extentsize)
244 339
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 340 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
341 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 342 $seq = $db->sequence (U32 flags = 0)
247 343
248=head4 example 344=head4 Example:
249 345
250 my $db = db_create $env; 346 my $db = db_create $env;
251 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600; 347 db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0600;
252 348
253 for (1..1000) { 349 for (1..1000) {
… …
269 DESTROY (DB_TXN_ornull *txn) 365 DESTROY (DB_TXN_ornull *txn)
270 CODE: 366 CODE:
271 if (txn) 367 if (txn)
272 txn->abort (txn); 368 txn->abort (txn);
273 369
274 $int = $txn->set_timeout (NV timeout, U32 flags) 370 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
371 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
372
373 $bool = $txn->failed
374 # see db_txn_finish documentation, above
275 375
276 376
277=head3 DBC/cursor methods 377=head3 DBC/cursor methods
278 378
279Methods available on DBC/$dbc handles: 379Methods available on DBC/$dbc handles:
… …
281 DESTROY (DBC_ornull *dbc) 381 DESTROY (DBC_ornull *dbc)
282 CODE: 382 CODE:
283 if (dbc) 383 if (dbc)
284 dbc->c_close (dbc); 384 dbc->c_close (dbc);
285 385
286=head4 example 386=head4 Example:
287 387
288 my $c = $db->cursor; 388 my $c = $db->cursor;
289 389
290 for (;;) { 390 for (;;) {
291 db_c_get $c, my $key, my $data, BDB::NEXT; 391 db_c_get $c, my $key, my $data, BDB::NEXT;
… …
293 last if $!; 393 last if $!;
294 } 394 }
295 395
296 db_c_close $c; 396 db_c_close $c;
297 397
398
298=head3 DB_SEQUENCE/sequence methods 399=head3 DB_SEQUENCE/sequence methods
299 400
300Methods available on DB_SEQUENCE/$seq handles: 401Methods available on DB_SEQUENCE/$seq handles:
301 402
302 DESTROY (DB_SEQUENCE_ornull *seq) 403 DESTROY (DB_SEQUENCE_ornull *seq)
… …
305 seq->close (seq, 0); 406 seq->close (seq, 0);
306 407
307 $int = $seq->initial_value (db_seq_t value) 408 $int = $seq->initial_value (db_seq_t value)
308 $int = $seq->set_cachesize (U32 size) 409 $int = $seq->set_cachesize (U32 size)
309 $int = $seq->set_flags (U32 flags) 410 $int = $seq->set_flags (U32 flags)
411 flags: SEQ_DEC SEQ_INC SEQ_WRAP
310 $int = $seq->set_range (db_seq_t min, db_seq_t max) 412 $int = $seq->set_range (db_seq_t min, db_seq_t max)
311 413
312=head4 example 414=head4 Example:
313 415
314 my $seq = $db->sequence; 416 my $seq = $db->sequence;
315 417
316 db_sequence_open $seq, undef, "seq", BDB::CREATE; 418 db_sequence_open $seq, undef, "seq", BDB::CREATE;
317 db_sequence_get $seq, undef, 1, my $value; 419 db_sequence_get $seq, undef, 1, my $value;
… …
368interactiveness when perl is not fast enough to process all requests in 470interactiveness when perl is not fast enough to process all requests in
369time. 471time.
370 472
371For interactive programs, values such as C<0.01> to C<0.1> should be fine. 473For interactive programs, values such as C<0.01> to C<0.1> should be fine.
372 474
373Example: Install an Event watcher that automatically calls 475Example: Install an EV watcher that automatically calls
374BDB::poll_cb with low priority, to ensure that other parts of the 476BDB::poll_cb with low priority, to ensure that other parts of the
375program get the CPU sometimes even under high AIO load. 477program get the CPU sometimes even under high load.
376 478
377 # try not to spend much more than 0.1s in poll_cb 479 # try not to spend much more than 0.1s in poll_cb
378 BDB::max_poll_time 0.1; 480 BDB::max_poll_time 0.1;
379 481
380 # use a low priority so other tasks have priority 482 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
381 Event->io (fd => BDB::poll_fileno,
382 poll => 'r', nice => 1,
383 cb => &BDB::poll_cb);
384 483
385=item BDB::poll_wait 484=item BDB::poll_wait
386 485
387If there are any outstanding requests and none of them in the result 486If there are any outstanding requests and none of them in the result
388phase, wait till the result filehandle becomes ready for reading (simply 487phase, wait till the result filehandle becomes ready for reading (simply
… …
400 499
401 BDB::poll_wait, BDB::poll_cb 500 BDB::poll_wait, BDB::poll_cb
402 501
403=item BDB::flush 502=item BDB::flush
404 503
405Wait till all outstanding AIO requests have been handled. 504Wait till all outstanding BDB requests have been handled.
406 505
407Strictly equivalent to: 506Strictly equivalent to:
408 507
409 BDB::poll_wait, BDB::poll_cb 508 BDB::poll_wait, BDB::poll_cb
410 while BDB::nreqs; 509 while BDB::nreqs;
… …
415 514
416=over 4 515=over 4
417 516
418=item BDB::min_parallel $nthreads 517=item BDB::min_parallel $nthreads
419 518
420Set the minimum number of AIO threads to C<$nthreads>. The current 519Set the minimum number of BDB threads to C<$nthreads>. The current
421default is C<8>, which means eight asynchronous operations can execute 520default is C<8>, which means eight asynchronous operations can execute
422concurrently at any one time (the number of outstanding requests, 521concurrently at any one time (the number of outstanding requests,
423however, is unlimited). 522however, is unlimited).
424 523
425BDB starts threads only on demand, when an AIO request is queued and 524BDB starts threads only on demand, when an BDB request is queued and
426no free thread exists. Please note that queueing up a hundred requests can 525no free thread exists. Please note that queueing up a hundred requests can
427create demand for a hundred threads, even if it turns out that everything 526create demand for a hundred threads, even if it turns out that everything
428is in the cache and could have been processed faster by a single thread. 527is in the cache and could have been processed faster by a single thread.
429 528
430It is recommended to keep the number of threads relatively low, as some 529It is recommended to keep the number of threads relatively low, as some
… …
435Under most circumstances you don't need to call this function, as the 534Under most circumstances you don't need to call this function, as the
436module selects a default that is suitable for low to moderate load. 535module selects a default that is suitable for low to moderate load.
437 536
438=item BDB::max_parallel $nthreads 537=item BDB::max_parallel $nthreads
439 538
440Sets the maximum number of AIO threads to C<$nthreads>. If more than the 539Sets the maximum number of BDB threads to C<$nthreads>. If more than the
441specified number of threads are currently running, this function kills 540specified number of threads are currently running, this function kills
442them. This function blocks until the limit is reached. 541them. This function blocks until the limit is reached.
443 542
444While C<$nthreads> are zero, aio requests get queued but not executed 543While C<$nthreads> are zero, aio requests get queued but not executed
445until the number of threads has been increased again. 544until the number of threads has been increased again.
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548 647
549=head2 FORK BEHAVIOUR 648=head2 FORK BEHAVIOUR
550 649
551This module should do "the right thing" when the process using it forks: 650This module should do "the right thing" when the process using it forks:
552 651
553Before the fork, IO::AIO enters a quiescent state where no requests 652Before the fork, BDB enters a quiescent state where no requests
554can be added in other threads and no results will be processed. After 653can be added in other threads and no results will be processed. After
555the fork the parent simply leaves the quiescent state and continues 654the fork the parent simply leaves the quiescent state and continues
556request/result processing, while the child frees the request/result queue 655request/result processing, while the child frees the request/result queue
557(so that the requests started before the fork will only be handled in the 656(so that the requests started before the fork will only be handled in the
558parent). Threads will be started on demand until the limit set in the 657parent). Threads will be started on demand until the limit set in the
559parent process has been reached again. 658parent process has been reached again.
560 659
561In short: the parent will, after a short pause, continue as if fork had 660In short: the parent will, after a short pause, continue as if fork had
562not been called, while the child will act as if IO::AIO has not been used 661not been called, while the child will act as if BDB has not been used
563yet. 662yet.
564 663
565=head2 MEMORY USAGE 664=head2 MEMORY USAGE
566 665
567Per-request usage: 666Per-request usage:
… …
570bytes of memory. In addition, stat requests need a stat buffer (possibly 669bytes of memory. In addition, stat requests need a stat buffer (possibly
571a few hundred bytes), readdir requires a result buffer and so on. Perl 670a few hundred bytes), readdir requires a result buffer and so on. Perl
572scalars and other data passed into aio requests will also be locked and 671scalars and other data passed into aio requests will also be locked and
573will consume memory till the request has entered the done state. 672will consume memory till the request has entered the done state.
574 673
575This is now awfully much, so queuing lots of requests is not usually a 674This is not awfully much, so queuing lots of requests is not usually a
576problem. 675problem.
577 676
578Per-thread usage: 677Per-thread usage:
579 678
580In the execution phase, some aio requests require more memory for 679In the execution phase, some aio requests require more memory for
581temporary buffers, and each thread requires a stack and other data 680temporary buffers, and each thread requires a stack and other data
582structures (usually around 16k-128k, depending on the OS). 681structures (usually around 16k-128k, depending on the OS).
583 682
584=head1 KNOWN BUGS 683=head1 KNOWN BUGS
585 684
586Known bugs will be fixed in the next release. 685Known bugs will be fixed in the next release, except:
686
687 If you use a transaction in any request, and the request returns
688 with an operating system error or DB_LOCK_NOTGRANTED, the internal
689 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
690 above.
587 691
588=head1 SEE ALSO 692=head1 SEE ALSO
589 693
590L<Coro::AIO>. 694L<Coro::BDB>, L<IO::AIO>.
591 695
592=head1 AUTHOR 696=head1 AUTHOR
593 697
594 Marc Lehmann <schmorp@schmorp.de> 698 Marc Lehmann <schmorp@schmorp.de>
595 http://home.schmorp.de/ 699 http://home.schmorp.de/

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