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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 1.29 by root, Sat Dec 22 07:33:48 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 # when you also use Coro, management is easy:
30 use Coro::BDB;
31
32 # automatic result processing with AnyEvent:
33 our $FH; open $FH, "<&=" . BDB::poll_fileno;
34 our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
35
36 # automatic result processing with EV:
37 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
38
39 # with Glib:
40 add_watch Glib::IO BDB::poll_fileno,
41 in => sub { BDB::poll_cb; 1 };
42
43 # or simply flush manually
44 BDB::flush;
45
8 46
9=head1 DESCRIPTION 47=head1 DESCRIPTION
10 48
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 49See 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). 50The BDB API is very similar to the C API (the translation has been very faithful).
… …
72use strict 'vars'; 110use strict 'vars';
73 111
74use base 'Exporter'; 112use base 'Exporter';
75 113
76BEGIN { 114BEGIN {
77 our $VERSION = '1.0'; 115 our $VERSION = '1.41';
78 116
79 our @BDB_REQ = qw( 117 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 118 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 119 db_env_memp_sync db_env_memp_trickle
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 120 db_open db_close db_compact db_sync db_upgrade
121 db_put db_get db_pget db_del db_key_range
83 db_txn_commit db_txn_abort 122 db_txn_commit db_txn_abort db_txn_finish
84 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del 123 db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
85 db_sequence_open db_sequence_close 124 db_sequence_open db_sequence_close
86 db_sequence_get db_sequence_remove 125 db_sequence_get db_sequence_remove
87 ); 126 );
88 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create)); 127 our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
… …
99 138
100=head2 BERKELEYDB FUNCTIONS 139=head2 BERKELEYDB FUNCTIONS
101 140
102All of these are functions. The create functions simply return a new 141All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 142object and never block. All the remaining functions all take an optional
104callback as last argument. If it is missing, then the fucntion will be 143callback as last argument. If it is missing, then the function will be
105executed synchronously. 144executed synchronously. In both cases, C<$!> will reflect the return value
145of the function.
106 146
107BDB functions that cannot block (mostly functions that manipulate 147BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 148settings) are method calls on the relevant objects, so the rule of thumb
109is: if its a method, its not blocking, if its a function, it takes a 149is: if its a method, its not blocking, if its a function, it takes a
110callback as last argument. 150callback as last argument.
… …
126=head3 BDB functions 166=head3 BDB functions
127 167
128Functions in the BDB namespace, exported by default: 168Functions in the BDB namespace, exported by default:
129 169
130 $env = db_env_create (U32 env_flags = 0) 170 $env = db_env_create (U32 env_flags = 0)
171 flags: RPCCLIENT
131 172
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 173 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
174 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) 175 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) 176 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
177 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) 178 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
179 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) 180 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) 181 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
138 182
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 183 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
184 flags: XA_CREATE
140 185
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 186 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
187 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) 188 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
189 flags: DB_NOSYNC
190 db_upgrade (DB *db, octetstring file, U32 flags = 0, SV *callback = &PL_sv_undef)
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) 191 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)
192 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 193 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) 194 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) 195 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
196 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) 197 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
198 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) 199 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
200 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) 201 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) 202 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
203 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 204 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
205
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 206 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) 207 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) 208 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
209 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) 210 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
211 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) 212 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) 213 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 214
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 215 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
216 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 217 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) 218 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)
219 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 220 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
221 flags: TXN_NOSYNC
163 222
223=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
224
225This is not actually a Berkeley DB function but a BDB module
226extension. The background for this exytension is: It is very annoying to
227have to check every single BDB function for error returns and provide a
228codepath out of your transaction. While the BDB module still makes this
229possible, it contains the following extensions:
230
231When a transaction-protected function returns any operating system
232error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
233transaction. This flag is also set by Berkeley DB functions themselves
234when an operation fails with LOCK_DEADLOCK, and it causes all further
235operations on that transaction (including C<db_txn_commit>) to fail.
236
237The C<db_txn_finish> request will look at this flag, and, if it is set,
238will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
239if it isn't set to something else yet). If it isn't set, it will call
240C<db_txn_commit> and return the error normally.
241
242How to use this? Easy: just write your transaction normally:
243
244 my $txn = $db_env->txn_begin;
245 db_get $db, $txn, "key", my $data;
246 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
247 db_txn_finish $txn;
248 die "transaction failed" if $!;
249
250That is, handle only the expected errors. If something unexpected happens
251(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
252requests (db_put in this case) will simply be skipped (they will fail with
253LOCK_DEADLOCK) and the transaction will be aborted.
254
255You can use the C<< $txn->failed >> method to check wether a transaction
256has failed in this way and abort further processing (excluding
257C<db_txn_finish>).
164 258
165=head3 DB_ENV/database environment methods 259=head3 DB_ENV/database environment methods
166 260
167Methods available on DB_ENV/$env handles: 261Methods available on DB_ENV/$env handles:
168 262
… …
179 $int = $env->set_flags (U32 flags, int onoff) 273 $int = $env->set_flags (U32 flags, int onoff)
180 $env->set_errfile (FILE *errfile = 0) 274 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 275 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 276 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 277 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 278 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 279 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 280 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 281 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 282 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 283 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 284 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 285 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 286 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 287 $int = $env->set_lg_max (U32 max)
288 $int = $env->mutex_set_increment (U32 increment)
289 $int = $env->mutex_set_tas_spins (U32 tas_spins)
290 $int = $env->mutex_set_max (U32 max)
291 $int = $env->mutex_set_align (U32 align)
194 292
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 293 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
294 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
196 295
197=head4 Example: 296=head4 Example:
198 297
199 use AnyEvent; 298 use AnyEvent;
200 use BDB; 299 use BDB;
… …
229 SvREFCNT_dec (env); 328 SvREFCNT_dec (env);
230 } 329 }
231 330
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 331 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 332 $int = $db->set_flags (U32 flags)
333 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
334 Btree: DUP DUPSORT RECNUM REVSPLITOFF
335 Hash: DUP DUPSORT
336 Queue: INORDER
337 Recno: RENUMBER SNAPSHOT
338
234 $int = $db->set_encrypt (const char *password, U32 flags) 339 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 340 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 341 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 342 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 343 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 346 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 347 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 348 $int = $db->set_q_extentsize (U32 extentsize)
244 349
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 350 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
351 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 352 $seq = $db->sequence (U32 flags = 0)
247 353
248=head4 Example: 354=head4 Example:
249 355
250 my $db = db_create $env; 356 my $db = db_create $env;
… …
269 DESTROY (DB_TXN_ornull *txn) 375 DESTROY (DB_TXN_ornull *txn)
270 CODE: 376 CODE:
271 if (txn) 377 if (txn)
272 txn->abort (txn); 378 txn->abort (txn);
273 379
274 $int = $txn->set_timeout (NV timeout, U32 flags) 380 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
381 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
382
383 $bool = $txn->failed
384 # see db_txn_finish documentation, above
275 385
276 386
277=head3 DBC/cursor methods 387=head3 DBC/cursor methods
278 388
279Methods available on DBC/$dbc handles: 389Methods available on DBC/$dbc handles:
280 390
281 DESTROY (DBC_ornull *dbc) 391 DESTROY (DBC_ornull *dbc)
282 CODE: 392 CODE:
283 if (dbc) 393 if (dbc)
284 dbc->c_close (dbc); 394 dbc->c_close (dbc);
395
396 $int = $cursor->set_priority ($priority = PRIORITY_*)
285 397
286=head4 Example: 398=head4 Example:
287 399
288 my $c = $db->cursor; 400 my $c = $db->cursor;
289 401
… …
306 seq->close (seq, 0); 418 seq->close (seq, 0);
307 419
308 $int = $seq->initial_value (db_seq_t value) 420 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 421 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 422 $int = $seq->set_flags (U32 flags)
423 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 424 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 425
313=head4 Example: 426=head4 Example:
314 427
315 my $seq = $db->sequence; 428 my $seq = $db->sequence;
… …
321=head2 SUPPORT FUNCTIONS 434=head2 SUPPORT FUNCTIONS
322 435
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 436=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 437
325=over 4 438=over 4
439
440=item $msg = BDB::strerror [$errno]
441
442Returns the string corresponding to the given errno value. If no argument
443is given, use C<$!>.
326 444
327=item $fileno = BDB::poll_fileno 445=item $fileno = BDB::poll_fileno
328 446
329Return the I<request result pipe file descriptor>. This filehandle must be 447Return the I<request result pipe file descriptor>. This filehandle must be
330polled for reading by some mechanism outside this module (e.g. Event or 448polled for reading by some mechanism outside this module (e.g. Event or
… …
369interactiveness when perl is not fast enough to process all requests in 487interactiveness when perl is not fast enough to process all requests in
370time. 488time.
371 489
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 490For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 491
374Example: Install an Event watcher that automatically calls 492Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 493BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 494program get the CPU sometimes even under high load.
377 495
378 # try not to spend much more than 0.1s in poll_cb 496 # try not to spend much more than 0.1s in poll_cb
379 BDB::max_poll_time 0.1; 497 BDB::max_poll_time 0.1;
380 498
381 # use a low priority so other tasks have priority 499 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);
385 500
386=item BDB::poll_wait 501=item BDB::poll_wait
387 502
388If there are any outstanding requests and none of them in the result 503If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 504phase, wait till the result filehandle becomes ready for reading (simply
… …
401 516
402 BDB::poll_wait, BDB::poll_cb 517 BDB::poll_wait, BDB::poll_cb
403 518
404=item BDB::flush 519=item BDB::flush
405 520
406Wait till all outstanding AIO requests have been handled. 521Wait till all outstanding BDB requests have been handled.
407 522
408Strictly equivalent to: 523Strictly equivalent to:
409 524
410 BDB::poll_wait, BDB::poll_cb 525 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 526 while BDB::nreqs;
… …
416 531
417=over 4 532=over 4
418 533
419=item BDB::min_parallel $nthreads 534=item BDB::min_parallel $nthreads
420 535
421Set the minimum number of AIO threads to C<$nthreads>. The current 536Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 537default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 538concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 539however, is unlimited).
425 540
426BDB starts threads only on demand, when an AIO request is queued and 541BDB 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 542no 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 543create 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. 544is in the cache and could have been processed faster by a single thread.
430 545
431It is recommended to keep the number of threads relatively low, as some 546It 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 551Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 552module selects a default that is suitable for low to moderate load.
438 553
439=item BDB::max_parallel $nthreads 554=item BDB::max_parallel $nthreads
440 555
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 556Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 557specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 558them. This function blocks until the limit is reached.
444 559
445While C<$nthreads> are zero, aio requests get queued but not executed 560While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 561until the number of threads has been increased again.
… …
549 664
550=head2 FORK BEHAVIOUR 665=head2 FORK BEHAVIOUR
551 666
552This module should do "the right thing" when the process using it forks: 667This module should do "the right thing" when the process using it forks:
553 668
554Before the fork, IO::AIO enters a quiescent state where no requests 669Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 670can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 671the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 672request/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 673(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 674parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 675parent process has been reached again.
561 676
562In short: the parent will, after a short pause, continue as if fork had 677In 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 678not been called, while the child will act as if BDB has not been used
564yet. 679yet.
680
681Win32 note: there is no fork on win32, and perls emulation of it is too
682broken to be supported, so do not use BDB in a windows pseudo-fork, better
683yet, switch to a more capable platform.
565 684
566=head2 MEMORY USAGE 685=head2 MEMORY USAGE
567 686
568Per-request usage: 687Per-request usage:
569 688
… …
582temporary buffers, and each thread requires a stack and other data 701temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 702structures (usually around 16k-128k, depending on the OS).
584 703
585=head1 KNOWN BUGS 704=head1 KNOWN BUGS
586 705
587Known bugs will be fixed in the next release. 706Known bugs will be fixed in the next release, except:
707
708 If you use a transaction in any request, and the request returns
709 with an operating system error or DB_LOCK_NOTGRANTED, the internal
710 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
711 above.
588 712
589=head1 SEE ALSO 713=head1 SEE ALSO
590 714
591L<Coro::AIO>. 715L<Coro::BDB>, L<IO::AIO>.
592 716
593=head1 AUTHOR 717=head1 AUTHOR
594 718
595 Marc Lehmann <schmorp@schmorp.de> 719 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 720 http://home.schmorp.de/

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