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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 1.35 by root, Sun Mar 30 08:01:58 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 = '1.45';
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", $VERSION);
98} 137}
99 138
139=head2 WIN32 FILENAMES/DATABASE NAME MESS
140
141Perl on Win32 supports only ASCII filenames (the reason is that it abuses
142an internal flag to store wether a filename is Unicode or ANSI, but that
143flag is used for somethign else in the perl core, so there is no way to
144detect wether a filename is ANSI or Unicode-encoded). The BDB module
145tries to work around this issue by assuming that the filename is an ANSI
146filename and BDB was built for unicode support.
147
100=head2 BERKELEYDB FUNCTIONS 148=head2 BERKELEYDB FUNCTIONS
101 149
102All of these are functions. The create functions simply return a new 150All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 151object and never block. All the remaining functions take an optional
104callback as last argument. If it is missing, then the fucntion will be 152callback as last argument. If it is missing, then the function will be
105executed synchronously. 153executed synchronously. In both cases, C<$!> will reflect the return value
154of the function.
106 155
107BDB functions that cannot block (mostly functions that manipulate 156BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 157settings) 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 158is: if it's a method, it's not blocking, if it's a function, it takes a
110callback as last argument. 159callback as last argument.
111 160
112In the following, C<$int> signifies an integer return value, 161In the following, C<$int> signifies an integer return value,
113C<octetstring> is a "binary string" (i.e. a perl string with no character 162C<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 163indices >255), C<U32> is an unsigned 32 bit integer, C<int> is some
… …
126=head3 BDB functions 175=head3 BDB functions
127 176
128Functions in the BDB namespace, exported by default: 177Functions in the BDB namespace, exported by default:
129 178
130 $env = db_env_create (U32 env_flags = 0) 179 $env = db_env_create (U32 env_flags = 0)
180 flags: RPCCLIENT
131 181
132 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef) 182 db_env_open (DB_ENV *env, octetstring db_home, U32 open_flags, int mode, SV *callback = &PL_sv_undef)
183 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) 184 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) 185 db_env_txn_checkpoint (DB_ENV *env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
186 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) 187 db_env_lock_detect (DB_ENV *env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV *dummy = 0, SV *callback = &PL_sv_undef)
188 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) 189 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) 190 db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef)
138 191
139 $db = db_create (DB_ENV *env = 0, U32 flags = 0) 192 $db = db_create (DB_ENV *env = 0, U32 flags = 0)
193 flags: XA_CREATE
140 194
141 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) 195 db_open (DB *db, DB_TXN_ornull *txnid, octetstring file, octetstring database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
196 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) 197 db_close (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef)
198 flags: DB_NOSYNC
199 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) 200 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)
201 flags: FREELIST_ONLY FREE_SPACE
144 db_sync (DB *db, U32 flags = 0, SV *callback = &PL_sv_undef) 202 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) 203 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) 204 db_put (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
205 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) 206 db_get (DB *db, DB_TXN_ornull *txn, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
207 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) 208 db_pget (DB *db, DB_TXN_ornull *txn, SV *key, SV *pkey, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
209 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) 210 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) 211 db_txn_commit (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
212 flags: TXN_NOSYNC TXN_SYNC
151 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef) 213 db_txn_abort (DB_TXN *txn, SV *callback = &PL_sv_undef)
214
152 db_c_close (DBC *dbc, SV *callback = &PL_sv_undef) 215 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) 216 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) 217 db_c_put (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
218 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) 219 db_c_get (DBC *dbc, SV *key, SV *data, U32 flags = 0, SV *callback = &PL_sv_undef)
220 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) 221 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) 222 db_c_del (DBC *dbc, U32 flags = 0, SV *callback = &PL_sv_undef)
158 223
159 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef) 224 db_sequence_open (DB_SEQUENCE *seq, DB_TXN_ornull *txnid, SV *key, U32 flags = 0, SV *callback = &PL_sv_undef)
225 flags: CREATE EXCL
160 db_sequence_close (DB_SEQUENCE *seq, U32 flags = 0, SV *callback = &PL_sv_undef) 226 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) 227 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)
228 flags: TXN_NOSYNC
162 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef) 229 db_sequence_remove (DB_SEQUENCE *seq, DB_TXN_ornull *txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
230 flags: TXN_NOSYNC
163 231
232=head4 db_txn_finish (DB_TXN *txn, U32 flags = 0, SV *callback = &PL_sv_undef)
233
234This is not actually a Berkeley DB function but a BDB module
235extension. The background for this exytension is: It is very annoying to
236have to check every single BDB function for error returns and provide a
237codepath out of your transaction. While the BDB module still makes this
238possible, it contains the following extensions:
239
240When a transaction-protected function returns any operating system
241error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
242transaction. This flag is also set by Berkeley DB functions themselves
243when an operation fails with LOCK_DEADLOCK, and it causes all further
244operations on that transaction (including C<db_txn_commit>) to fail.
245
246The C<db_txn_finish> request will look at this flag, and, if it is set,
247will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
248if it isn't set to something else yet). If it isn't set, it will call
249C<db_txn_commit> and return the error normally.
250
251How to use this? Easy: just write your transaction normally:
252
253 my $txn = $db_env->txn_begin;
254 db_get $db, $txn, "key", my $data;
255 db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
256 db_txn_finish $txn;
257 die "transaction failed" if $!;
258
259That is, handle only the expected errors. If something unexpected happens
260(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
261requests (db_put in this case) will simply be skipped (they will fail with
262LOCK_DEADLOCK) and the transaction will be aborted.
263
264You can use the C<< $txn->failed >> method to check wether a transaction
265has failed in this way and abort further processing (excluding
266C<db_txn_finish>).
164 267
165=head3 DB_ENV/database environment methods 268=head3 DB_ENV/database environment methods
166 269
167Methods available on DB_ENV/$env handles: 270Methods available on DB_ENV/$env handles:
168 271
… …
179 $int = $env->set_flags (U32 flags, int onoff) 282 $int = $env->set_flags (U32 flags, int onoff)
180 $env->set_errfile (FILE *errfile = 0) 283 $env->set_errfile (FILE *errfile = 0)
181 $env->set_msgfile (FILE *msgfile = 0) 284 $env->set_msgfile (FILE *msgfile = 0)
182 $int = $env->set_verbose (U32 which, int onoff = 1) 285 $int = $env->set_verbose (U32 which, int onoff = 1)
183 $int = $env->set_encrypt (const char *password, U32 flags = 0) 286 $int = $env->set_encrypt (const char *password, U32 flags = 0)
184 $int = $env->set_timeout (NV timeout, U32 flags) 287 $int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
185 $int = $env->set_mp_max_openfd (int maxopenfd); 288 $int = $env->set_mp_max_openfd (int maxopenfd);
186 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep); 289 $int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
187 $int = $env->set_mp_mmapsize (int mmapsize_mb) 290 $int = $env->set_mp_mmapsize (int mmapsize_mb)
188 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT) 291 $int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
189 $int = $env->set_lk_max_lockers (U32 max) 292 $int = $env->set_lk_max_lockers (U32 max)
190 $int = $env->set_lk_max_locks (U32 max) 293 $int = $env->set_lk_max_locks (U32 max)
191 $int = $env->set_lk_max_objects (U32 max) 294 $int = $env->set_lk_max_objects (U32 max)
192 $int = $env->set_lg_bsize (U32 max) 295 $int = $env->set_lg_bsize (U32 max)
193 $int = $env->set_lg_max (U32 max) 296 $int = $env->set_lg_max (U32 max)
297 $int = $env->mutex_set_increment (U32 increment)
298 $int = $env->mutex_set_tas_spins (U32 tas_spins)
299 $int = $env->mutex_set_max (U32 max)
300 $int = $env->mutex_set_align (U32 align)
194 301
195 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 302 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
303 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
196 304
197=head4 Example: 305=head4 Example:
198 306
199 use AnyEvent; 307 use AnyEvent;
200 use BDB; 308 use BDB;
… …
229 SvREFCNT_dec (env); 337 SvREFCNT_dec (env);
230 } 338 }
231 339
232 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0) 340 $int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
233 $int = $db->set_flags (U32 flags) 341 $int = $db->set_flags (U32 flags)
342 flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
343 Btree: DUP DUPSORT RECNUM REVSPLITOFF
344 Hash: DUP DUPSORT
345 Queue: INORDER
346 Recno: RENUMBER SNAPSHOT
347
234 $int = $db->set_encrypt (const char *password, U32 flags) 348 $int = $db->set_encrypt (const char *password, U32 flags)
235 $int = $db->set_lorder (int lorder) 349 $int = $db->set_lorder (int lorder)
236 $int = $db->set_bt_minkey (U32 minkey) 350 $int = $db->set_bt_minkey (U32 minkey)
237 $int = $db->set_re_delim (int delim) 351 $int = $db->set_re_delim (int delim)
238 $int = $db->set_re_pad (int re_pad) 352 $int = $db->set_re_pad (int re_pad)
… …
241 $int = $db->set_h_ffactor (U32 h_ffactor) 355 $int = $db->set_h_ffactor (U32 h_ffactor)
242 $int = $db->set_h_nelem (U32 h_nelem) 356 $int = $db->set_h_nelem (U32 h_nelem)
243 $int = $db->set_q_extentsize (U32 extentsize) 357 $int = $db->set_q_extentsize (U32 extentsize)
244 358
245 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0) 359 $dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
360 flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
246 $seq = $db->sequence (U32 flags = 0) 361 $seq = $db->sequence (U32 flags = 0)
247 362
248=head4 Example: 363=head4 Example:
249 364
250 my $db = db_create $env; 365 my $db = db_create $env;
… …
269 DESTROY (DB_TXN_ornull *txn) 384 DESTROY (DB_TXN_ornull *txn)
270 CODE: 385 CODE:
271 if (txn) 386 if (txn)
272 txn->abort (txn); 387 txn->abort (txn);
273 388
274 $int = $txn->set_timeout (NV timeout, U32 flags) 389 $int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
390 flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
391
392 $bool = $txn->failed
393 # see db_txn_finish documentation, above
275 394
276 395
277=head3 DBC/cursor methods 396=head3 DBC/cursor methods
278 397
279Methods available on DBC/$dbc handles: 398Methods available on DBC/$dbc handles:
280 399
281 DESTROY (DBC_ornull *dbc) 400 DESTROY (DBC_ornull *dbc)
282 CODE: 401 CODE:
283 if (dbc) 402 if (dbc)
284 dbc->c_close (dbc); 403 dbc->c_close (dbc);
404
405 $int = $cursor->set_priority ($priority = PRIORITY_*)
285 406
286=head4 Example: 407=head4 Example:
287 408
288 my $c = $db->cursor; 409 my $c = $db->cursor;
289 410
… …
306 seq->close (seq, 0); 427 seq->close (seq, 0);
307 428
308 $int = $seq->initial_value (db_seq_t value) 429 $int = $seq->initial_value (db_seq_t value)
309 $int = $seq->set_cachesize (U32 size) 430 $int = $seq->set_cachesize (U32 size)
310 $int = $seq->set_flags (U32 flags) 431 $int = $seq->set_flags (U32 flags)
432 flags: SEQ_DEC SEQ_INC SEQ_WRAP
311 $int = $seq->set_range (db_seq_t min, db_seq_t max) 433 $int = $seq->set_range (db_seq_t min, db_seq_t max)
312 434
313=head4 Example: 435=head4 Example:
314 436
315 my $seq = $db->sequence; 437 my $seq = $db->sequence;
… …
321=head2 SUPPORT FUNCTIONS 443=head2 SUPPORT FUNCTIONS
322 444
323=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION 445=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
324 446
325=over 4 447=over 4
448
449=item $msg = BDB::strerror [$errno]
450
451Returns the string corresponding to the given errno value. If no argument
452is given, use C<$!>.
453
454Note that the BDB module also patches the C<$!> variable directly, so you
455should be able to get a bdb error string by simply stringifying C<$!>.
326 456
327=item $fileno = BDB::poll_fileno 457=item $fileno = BDB::poll_fileno
328 458
329Return the I<request result pipe file descriptor>. This filehandle must be 459Return the I<request result pipe file descriptor>. This filehandle must be
330polled for reading by some mechanism outside this module (e.g. Event or 460polled for reading by some mechanism outside this module (e.g. Event or
… …
369interactiveness when perl is not fast enough to process all requests in 499interactiveness when perl is not fast enough to process all requests in
370time. 500time.
371 501
372For interactive programs, values such as C<0.01> to C<0.1> should be fine. 502For interactive programs, values such as C<0.01> to C<0.1> should be fine.
373 503
374Example: Install an Event watcher that automatically calls 504Example: Install an EV watcher that automatically calls
375BDB::poll_cb with low priority, to ensure that other parts of the 505BDB::poll_cb with low priority, to ensure that other parts of the
376program get the CPU sometimes even under high AIO load. 506program get the CPU sometimes even under high load.
377 507
378 # try not to spend much more than 0.1s in poll_cb 508 # try not to spend much more than 0.1s in poll_cb
379 BDB::max_poll_time 0.1; 509 BDB::max_poll_time 0.1;
380 510
381 # use a low priority so other tasks have priority 511 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);
385 512
386=item BDB::poll_wait 513=item BDB::poll_wait
387 514
388If there are any outstanding requests and none of them in the result 515If there are any outstanding requests and none of them in the result
389phase, wait till the result filehandle becomes ready for reading (simply 516phase, wait till the result filehandle becomes ready for reading (simply
… …
401 528
402 BDB::poll_wait, BDB::poll_cb 529 BDB::poll_wait, BDB::poll_cb
403 530
404=item BDB::flush 531=item BDB::flush
405 532
406Wait till all outstanding AIO requests have been handled. 533Wait till all outstanding BDB requests have been handled.
407 534
408Strictly equivalent to: 535Strictly equivalent to:
409 536
410 BDB::poll_wait, BDB::poll_cb 537 BDB::poll_wait, BDB::poll_cb
411 while BDB::nreqs; 538 while BDB::nreqs;
… …
416 543
417=over 4 544=over 4
418 545
419=item BDB::min_parallel $nthreads 546=item BDB::min_parallel $nthreads
420 547
421Set the minimum number of AIO threads to C<$nthreads>. The current 548Set the minimum number of BDB threads to C<$nthreads>. The current
422default is C<8>, which means eight asynchronous operations can execute 549default is C<8>, which means eight asynchronous operations can execute
423concurrently at any one time (the number of outstanding requests, 550concurrently at any one time (the number of outstanding requests,
424however, is unlimited). 551however, is unlimited).
425 552
426BDB starts threads only on demand, when an AIO request is queued and 553BDB 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 554no 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 555create 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. 556is in the cache and could have been processed faster by a single thread.
430 557
431It is recommended to keep the number of threads relatively low, as some 558It 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 563Under most circumstances you don't need to call this function, as the
437module selects a default that is suitable for low to moderate load. 564module selects a default that is suitable for low to moderate load.
438 565
439=item BDB::max_parallel $nthreads 566=item BDB::max_parallel $nthreads
440 567
441Sets the maximum number of AIO threads to C<$nthreads>. If more than the 568Sets the maximum number of BDB threads to C<$nthreads>. If more than the
442specified number of threads are currently running, this function kills 569specified number of threads are currently running, this function kills
443them. This function blocks until the limit is reached. 570them. This function blocks until the limit is reached.
444 571
445While C<$nthreads> are zero, aio requests get queued but not executed 572While C<$nthreads> are zero, aio requests get queued but not executed
446until the number of threads has been increased again. 573until the number of threads has been increased again.
… …
549 676
550=head2 FORK BEHAVIOUR 677=head2 FORK BEHAVIOUR
551 678
552This module should do "the right thing" when the process using it forks: 679This module should do "the right thing" when the process using it forks:
553 680
554Before the fork, IO::AIO enters a quiescent state where no requests 681Before the fork, BDB enters a quiescent state where no requests
555can be added in other threads and no results will be processed. After 682can be added in other threads and no results will be processed. After
556the fork the parent simply leaves the quiescent state and continues 683the fork the parent simply leaves the quiescent state and continues
557request/result processing, while the child frees the request/result queue 684request/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 685(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 686parent). Threads will be started on demand until the limit set in the
560parent process has been reached again. 687parent process has been reached again.
561 688
562In short: the parent will, after a short pause, continue as if fork had 689In 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 690not been called, while the child will act as if BDB has not been used
564yet. 691yet.
692
693Win32 note: there is no fork on win32, and perls emulation of it is too
694broken to be supported, so do not use BDB in a windows pseudo-fork, better
695yet, switch to a more capable platform.
565 696
566=head2 MEMORY USAGE 697=head2 MEMORY USAGE
567 698
568Per-request usage: 699Per-request usage:
569 700
… …
582temporary buffers, and each thread requires a stack and other data 713temporary buffers, and each thread requires a stack and other data
583structures (usually around 16k-128k, depending on the OS). 714structures (usually around 16k-128k, depending on the OS).
584 715
585=head1 KNOWN BUGS 716=head1 KNOWN BUGS
586 717
587Known bugs will be fixed in the next release. 718Known bugs will be fixed in the next release, except:
719
720 If you use a transaction in any request, and the request returns
721 with an operating system error or DB_LOCK_NOTGRANTED, the internal
722 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
723 above.
588 724
589=head1 SEE ALSO 725=head1 SEE ALSO
590 726
591L<Coro::AIO>. 727L<Coro::BDB>, L<IO::AIO>.
592 728
593=head1 AUTHOR 729=head1 AUTHOR
594 730
595 Marc Lehmann <schmorp@schmorp.de> 731 Marc Lehmann <schmorp@schmorp.de>
596 http://home.schmorp.de/ 732 http://home.schmorp.de/

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