ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/BDB/BDB.pm
(Generate patch)

Comparing BDB/BDB.pm (file contents):
Revision 1.13 by root, Mon Aug 13 12:07:55 2007 UTC vs.
Revision 1.34 by root, Sun Mar 30 06:17:31 2008 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 = '1.44';
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));
… …
95 134
96 require XSLoader; 135 require XSLoader;
97 XSLoader::load ("BDB", $VERSION); 136 XSLoader::load ("BDB", $VERSION);
98} 137}
99 138
139=head2 FILENAMES/DATABASE NAMES
140
141The BDB expects "binary" filenames (octet strings) for pathnames on POSIX
142systems, and "unicode" filenames (strings with characters potentially
143>255) on Win32 (expecting a Unicode win32 build - win32 is a total mess).
144
100=head2 BERKELEYDB FUNCTIONS 145=head2 BERKELEYDB FUNCTIONS
101 146
102All of these are functions. The create functions simply return a new 147All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 148object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 149callback as last argument. If it is missing, then the function will be
105executed synchronously. 150executed synchronously. In both cases, C<$!> will reflect the return value
151of the function.
106 152
107BDB functions that cannot block (mostly functions that manipulate 153BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 154settings) 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 155is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 156callback as last argument.
111 157
112In the following, C<$int> signifies an integer return value, 158In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 159C<octetstring> is a "binary string" (i.e. a perl string with no character
114indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some 160indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
… …
126=head3 BDB functions 172=head3 BDB functions
127 173
128Functions in the BDB namespace, exported by default: 174Functions in the BDB namespace, exported by default:
129 175
130 $env = db_env_create (U32 env_flags = 0) 176 $env = db_env_create (U32 env_flags = 0)
177 flags: RPCCLIENT
131 178
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 179 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
180 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) 181 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) 182 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
183 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) 184 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
185 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) 186 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) 187 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
138 188
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 189 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
190 flags: XA_CREATE
140 191
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 192 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
193 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) 194 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
195 flags: DB_NOSYNC
196 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) 197 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)
198 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 199 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) 200 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) 201 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
202 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) 203 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
204 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) 205 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
206 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) 207 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) 208 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
209 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 210 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
211
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 212 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) 213 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) 214 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
215 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) 216 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
217 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) 218 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) 219 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 220
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 221 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
222 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 223 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) 224 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)
225 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 226 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
227 flags: TXN_NOSYNC
163 228
229=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
230
231This is not actually a Berkeley DB function but a BDB module
232extension. The background for this exytension is: It is very annoying to
233have to check every single BDB function for error returns and provide a
234codepath out of your transaction. While the BDB module still makes this
235possible, it contains the following extensions:
236
237When a transaction-protected function returns any operating system
238error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
239transaction. This flag is also set by Berkeley DB functions themselves
240when an operation fails with LOCK_DEADLOCK, and it causes all further
241operations on that transaction (including C<db_txn_commit>) to fail.
242
243The C<db_txn_finish> request will look at this flag, and, if it is set,
244will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
245if it isn't set to something else yet). If it isn't set, it will call
246C<db_txn_commit> and return the error normally.
247
248How to use this? Easy: just write your transaction normally:
249
250 my $txn = $db_env->txn_begin;
251 db_get $db, $txn, "key", my $data;
252 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
253 db_txn_finish $txn;
254 die "transaction failed" if $!;
255
256That is, handle only the expected errors. If something unexpected happens
257(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
258requests (db_put in this case) will simply be skipped (they will fail with
259LOCK_DEADLOCK) and the transaction will be aborted.
260
261You can use the C<< $txn->failed >> method to check wether a transaction
262has failed in this way and abort further processing (excluding
263C<db_txn_finish>).
164 264
165=head3 DB_ENV/database environment methods 265=head3 DB_ENV/database environment methods
166 266
167Methods available on DB_ENV/$env handles: 267Methods available on DB_ENV/$env handles:
168 268
… …
179 $int = $env->set_flags (U32 flags, int onoff) 279 $int = $env->set_flags (U32 flags, int onoff)
180 $env->set_errfile (FILE *errfile = 0) 280 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 281 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 282 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 283 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 284 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 285 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 286 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 287 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 288 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 289 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 290 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 291 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 292 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 293 $int = $env->set_lg_max (U32 max)
294 $int = $env->mutex_set_increment (U32 increment)
295 $int = $env->mutex_set_tas_spins (U32 tas_spins)
296 $int = $env->mutex_set_max (U32 max)
297 $int = $env->mutex_set_align (U32 align)
194 298
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 299 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
300 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
196 301
197=head4 Example: 302=head4 Example:
198 303
199 use AnyEvent; 304 use AnyEvent;
200 use BDB; 305 use BDB;
… …
229 SvREFCNT_dec (env); 334 SvREFCNT_dec (env);
230 } 335 }
231 336
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 337 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 338 $int = $db->set_flags (U32 flags)
339 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
340 Btree: DUP DUPSORT RECNUM REVSPLITOFF
341 Hash: DUP DUPSORT
342 Queue: INORDER
343 Recno: RENUMBER SNAPSHOT
344
234 $int = $db->set_encrypt (const char *password, U32 flags) 345 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 346 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 347 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 348 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 349 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 352 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 353 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 354 $int = $db->set_q_extentsize (U32 extentsize)
244 355
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 356 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
357 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 358 $seq = $db->sequence (U32 flags = 0)
247 359
248=head4 Example: 360=head4 Example:
249 361
250 my $db = db_create $env; 362 my $db = db_create $env;
… …
269 DESTROY (DB_TXN_ornull *txn) 381 DESTROY (DB_TXN_ornull *txn)
270 CODE: 382 CODE:
271 if (txn) 383 if (txn)
272 txn->abort (txn); 384 txn->abort (txn);
273 385
274 $int = $txn->set_timeout (NV timeout, U32 flags) 386 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
387 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
388
389 $bool = $txn->failed
390 # see db_txn_finish documentation, above
275 391
276 392
277=head3 DBC/cursor methods 393=head3 DBC/cursor methods
278 394
279Methods available on DBC/$dbc handles: 395Methods available on DBC/$dbc handles:
280 396
281 DESTROY (DBC_ornull *dbc) 397 DESTROY (DBC_ornull *dbc)
282 CODE: 398 CODE:
283 if (dbc) 399 if (dbc)
284 dbc->c_close (dbc); 400 dbc->c_close (dbc);
401
402 $int = $cursor->set_priority ($priority = PRIORITY_*)
285 403
286=head4 Example: 404=head4 Example:
287 405
288 my $c = $db->cursor; 406 my $c = $db->cursor;
289 407
… …
306 seq->close (seq, 0); 424 seq->close (seq, 0);
307 425
308 $int = $seq->initial_value (db_seq_t value) 426 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 427 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 428 $int = $seq->set_flags (U32 flags)
429 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 430 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 431
313=head4 Example: 432=head4 Example:
314 433
315 my $seq = $db->sequence; 434 my $seq = $db->sequence;
… …
321=head2 SUPPORT FUNCTIONS 440=head2 SUPPORT FUNCTIONS
322 441
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 442=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 443
325=over 4 444=over 4
445
446=item $msg = BDB::strerror [$errno]
447
448Returns the string corresponding to the given errno value. If no argument
449is given, use C<$!>.
450
451Note that the BDB module also patches the C<$!> variable directly, so you
452should be able to get a bdb error string by simply stringifying C<$!>.
326 453
327=item $fileno = BDB::poll_fileno 454=item $fileno = BDB::poll_fileno
328 455
329Return the I<request result pipe file descriptor>. This filehandle must be 456Return the I<request result pipe file descriptor>. This filehandle must be
330polled for reading by some mechanism outside this module (e.g. Event or 457polled for reading by some mechanism outside this module (e.g. Event or
… …
369interactiveness when perl is not fast enough to process all requests in 496interactiveness when perl is not fast enough to process all requests in
370time. 497time.
371 498
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 499For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 500
374Example: Install an Event watcher that automatically calls 501Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 502BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 503program get the CPU sometimes even under high load.
377 504
378 # try not to spend much more than 0.1s in poll_cb 505 # try not to spend much more than 0.1s in poll_cb
379 BDB::max_poll_time 0.1; 506 BDB::max_poll_time 0.1;
380 507
381 # use a low priority so other tasks have priority 508 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);
385 509
386=item BDB::poll_wait 510=item BDB::poll_wait
387 511
388If there are any outstanding requests and none of them in the result 512If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 513phase, wait till the result filehandle becomes ready for reading (simply
… …
401 525
402 BDB::poll_wait, BDB::poll_cb 526 BDB::poll_wait, BDB::poll_cb
403 527
404=item BDB::flush 528=item BDB::flush
405 529
406Wait till all outstanding AIO requests have been handled. 530Wait till all outstanding BDB requests have been handled.
407 531
408Strictly equivalent to: 532Strictly equivalent to:
409 533
410 BDB::poll_wait, BDB::poll_cb 534 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 535 while BDB::nreqs;
… …
416 540
417=over 4 541=over 4
418 542
419=item BDB::min_parallel $nthreads 543=item BDB::min_parallel $nthreads
420 544
421Set the minimum number of AIO threads to C<$nthreads>. The current 545Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 546default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 547concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 548however, is unlimited).
425 549
426BDB starts threads only on demand, when an AIO request is queued and 550BDB 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 551no 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 552create 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. 553is in the cache and could have been processed faster by a single thread.
430 554
431It is recommended to keep the number of threads relatively low, as some 555It 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 560Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 561module selects a default that is suitable for low to moderate load.
438 562
439=item BDB::max_parallel $nthreads 563=item BDB::max_parallel $nthreads
440 564
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 565Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 566specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 567them. This function blocks until the limit is reached.
444 568
445While C<$nthreads> are zero, aio requests get queued but not executed 569While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 570until the number of threads has been increased again.
… …
549 673
550=head2 FORK BEHAVIOUR 674=head2 FORK BEHAVIOUR
551 675
552This module should do "the right thing" when the process using it forks: 676This module should do "the right thing" when the process using it forks:
553 677
554Before the fork, IO::AIO enters a quiescent state where no requests 678Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 679can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 680the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 681request/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 682(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 683parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 684parent process has been reached again.
561 685
562In short: the parent will, after a short pause, continue as if fork had 686In 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 687not been called, while the child will act as if BDB has not been used
564yet. 688yet.
689
690Win32 note: there is no fork on win32, and perls emulation of it is too
691broken to be supported, so do not use BDB in a windows pseudo-fork, better
692yet, switch to a more capable platform.
565 693
566=head2 MEMORY USAGE 694=head2 MEMORY USAGE
567 695
568Per-request usage: 696Per-request usage:
569 697
… …
582temporary buffers, and each thread requires a stack and other data 710temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 711structures (usually around 16k-128k, depending on the OS).
584 712
585=head1 KNOWN BUGS 713=head1 KNOWN BUGS
586 714
587Known bugs will be fixed in the next release. 715Known bugs will be fixed in the next release, except:
716
717 If you use a transaction in any request, and the request returns
718 with an operating system error or DB_LOCK_NOTGRANTED, the internal
719 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
720 above.
588 721
589=head1 SEE ALSO 722=head1 SEE ALSO
590 723
591L<Coro::AIO>. 724L<Coro::BDB>, L<IO::AIO>.
592 725
593=head1 AUTHOR 726=head1 AUTHOR
594 727
595 Marc Lehmann <schmorp@schmorp.de> 728 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 729 http://home.schmorp.de/

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines