… | |
… | |
86 | Request has reached the end of its lifetime and holds no resources |
86 | Request has reached the end of its lifetime and holds no resources |
87 | anymore (except possibly for the Perl object, but its connection to |
87 | anymore (except possibly for the Perl object, but its connection to |
88 | the actual aio request is severed and calling its methods will |
88 | the actual aio request is severed and calling its methods will |
89 | either do nothing or result in a runtime error). |
89 | either do nothing or result in a runtime error). |
90 | |
90 | |
91 | WIN32 FILENAMES/DATABASE NAME MESS |
|
|
92 | Perl on Win32 supports only ASCII filenames (the reason is that it |
|
|
93 | abuses an internal flag to store wether a filename is Unicode or ANSI, |
|
|
94 | but that flag is used for somethign else in the perl core, so there is |
|
|
95 | no way to detect wether a filename is ANSI or Unicode-encoded). The BDB |
|
|
96 | module tries to work around this issue by assuming that the filename is |
|
|
97 | an ANSI filename and BDB was built for unicode support. |
|
|
98 | |
|
|
99 | BERKELEYDB FUNCTIONS |
91 | BERKELEYDB FUNCTIONS |
100 | All of these are functions. The create functions simply return a new |
92 | All of these are functions. The create functions simply return a new |
101 | object and never block. All the remaining functions take an optional |
93 | object and never block. All the remaining functions take an optional |
102 | callback as last argument. If it is missing, then the function will be |
94 | callback as last argument. If it is missing, then the function will be |
103 | executed synchronously. In both cases, $! will reflect the return value |
95 | executed synchronously. In both cases, $! will reflect the return value |
104 | of the function. |
96 | of the function. |
… | |
… | |
142 | |
134 | |
143 | db_env_txn_checkpoint $db_env, 0, 0, 0, undef; |
135 | db_env_txn_checkpoint $db_env, 0, 0, 0, undef; |
144 | db_env_txn_checkpoint $db_env, 0, 0, 0; |
136 | db_env_txn_checkpoint $db_env, 0, 0, 0; |
145 | db_env_txn_checkpoint $db_env, 0; |
137 | db_env_txn_checkpoint $db_env, 0; |
146 | |
138 | |
147 | BDB functions |
139 | BDB functions |
148 | Functions in the BDB namespace, exported by default: |
140 | Functions in the BDB namespace, exported by default: |
149 | |
141 | |
150 | $env = db_env_create (U32 env_flags = 0) |
142 | $env = db_env_create (U32 env_flags = 0) |
151 | flags: RPCCLIENT |
143 | flags: RPCCLIENT |
152 | |
144 | |
… | |
… | |
159 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
151 | atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST |
160 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
152 | db_env_memp_sync (DB_ENV *env, SV *dummy = 0, SV *callback = &PL_sv_undef) |
161 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
153 | db_env_memp_trickle (DB_ENV *env, int percent, SV *dummy = 0, SV *callback = &PL_sv_undef) |
162 | db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef) |
154 | db_env_dbremove (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef) |
163 | db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef) |
155 | db_env_dbrename (DB_ENV *env, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef) |
|
|
156 | db_env_log_archive (DB_ENV *env, SV *listp, U32 flags = 0, SV *callback = &PL_sv_undef) |
164 | |
157 | |
165 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
158 | $db = db_create (DB_ENV *env = 0, U32 flags = 0) |
166 | flags: XA_CREATE |
159 | flags: XA_CREATE |
167 | |
160 | |
168 | db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
161 | db_open (DB *db, DB_TXN_ornull *txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef) |
… | |
… | |
236 | |
229 | |
237 | You can use the "$txn->failed" method to check wether a transaction has |
230 | You can use the "$txn->failed" method to check wether a transaction has |
238 | failed in this way and abort further processing (excluding |
231 | failed in this way and abort further processing (excluding |
239 | "db_txn_finish"). |
232 | "db_txn_finish"). |
240 | |
233 | |
241 | DB_ENV/database environment methods |
234 | DB_ENV/database environment methods |
242 | Methods available on DB_ENV/$env handles: |
235 | Methods available on DB_ENV/$env handles: |
243 | |
236 | |
244 | DESTROY (DB_ENV_ornull *env) |
237 | DESTROY (DB_ENV_ornull *env) |
245 | CODE: |
238 | CODE: |
246 | if (env) |
239 | if (env) |
… | |
… | |
295 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
288 | BDB::INIT_LOCK | BDB::INIT_LOG | BDB::INIT_MPOOL | BDB::INIT_TXN | BDB::RECOVER | BDB::USE_ENVIRON | BDB::CREATE, |
296 | 0600; |
289 | 0600; |
297 | |
290 | |
298 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
291 | $env->set_flags (BDB::AUTO_COMMIT | BDB::TXN_NOSYNC, 1); |
299 | |
292 | |
300 | DB/database methods |
293 | DB/database methods |
301 | Methods available on DB/$db handles: |
294 | Methods available on DB/$db handles: |
302 | |
295 | |
303 | DESTROY (DB_ornull *db) |
296 | DESTROY (DB_ornull *db) |
304 | CODE: |
297 | CODE: |
305 | if (db) |
298 | if (db) |
… | |
… | |
345 | |
338 | |
346 | db_del $db, undef, "key $_" for 1..1000; |
339 | db_del $db, undef, "key $_" for 1..1000; |
347 | |
340 | |
348 | db_sync $db; |
341 | db_sync $db; |
349 | |
342 | |
350 | DB_TXN/transaction methods |
343 | DB_TXN/transaction methods |
351 | Methods available on DB_TXN/$txn handles: |
344 | Methods available on DB_TXN/$txn handles: |
352 | |
345 | |
353 | DESTROY (DB_TXN_ornull *txn) |
346 | DESTROY (DB_TXN_ornull *txn) |
354 | CODE: |
347 | CODE: |
355 | if (txn) |
348 | if (txn) |
… | |
… | |
359 | flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT |
352 | flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT |
360 | |
353 | |
361 | $bool = $txn->failed |
354 | $bool = $txn->failed |
362 | # see db_txn_finish documentation, above |
355 | # see db_txn_finish documentation, above |
363 | |
356 | |
364 | DBC/cursor methods |
357 | DBC/cursor methods |
365 | Methods available on DBC/$dbc handles: |
358 | Methods available on DBC/$dbc handles: |
366 | |
359 | |
367 | DESTROY (DBC_ornull *dbc) |
360 | DESTROY (DBC_ornull *dbc) |
368 | CODE: |
361 | CODE: |
369 | if (dbc) |
362 | if (dbc) |
… | |
… | |
380 | last if $!; |
373 | last if $!; |
381 | } |
374 | } |
382 | |
375 | |
383 | db_c_close $c; |
376 | db_c_close $c; |
384 | |
377 | |
385 | DB_SEQUENCE/sequence methods |
378 | DB_SEQUENCE/sequence methods |
386 | Methods available on DB_SEQUENCE/$seq handles: |
379 | Methods available on DB_SEQUENCE/$seq handles: |
387 | |
380 | |
388 | DESTROY (DB_SEQUENCE_ornull *seq) |
381 | DESTROY (DB_SEQUENCE_ornull *seq) |
389 | CODE: |
382 | CODE: |
390 | if (seq) |
383 | if (seq) |
… | |
… | |
400 | my $seq = $db->sequence; |
393 | my $seq = $db->sequence; |
401 | |
394 | |
402 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
395 | db_sequence_open $seq, undef, "seq", BDB::CREATE; |
403 | db_sequence_get $seq, undef, 1, my $value; |
396 | db_sequence_get $seq, undef, 1, my $value; |
404 | |
397 | |
405 | SUPPORT FUNCTIONS |
398 | SUPPORT FUNCTIONS |
406 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
399 | EVENT PROCESSING AND EVENT LOOP INTEGRATION |
407 | $msg = BDB::strerror [$errno] |
400 | $msg = BDB::strerror [$errno] |
408 | Returns the string corresponding to the given errno value. If no |
401 | Returns the string corresponding to the given errno value. If no |
409 | argument is given, use $!. |
402 | argument is given, use $!. |
410 | |
403 | |
411 | Note that the BDB module also patches the $! variable directly, so |
404 | Note that the BDB module also patches the $! variable directly, so |
… | |
… | |
488 | Strictly equivalent to: |
481 | Strictly equivalent to: |
489 | |
482 | |
490 | BDB::poll_wait, BDB::poll_cb |
483 | BDB::poll_wait, BDB::poll_cb |
491 | while BDB::nreqs; |
484 | while BDB::nreqs; |
492 | |
485 | |
493 | VERSION CHECKING |
486 | VERSION CHECKING |
494 | BerkeleyDB comes in various versions, many of them have minor |
487 | BerkeleyDB comes in various versions, many of them have minor |
495 | incompatibilities. This means that traditional "at least version x.x" |
488 | incompatibilities. This means that traditional "at least version x.x" |
496 | checks are often not sufficient. |
489 | checks are often not sufficient. |
497 | |
490 | |
498 | Example: set the log_autoremove option in a way compatible with <v4.7 |
491 | Example: set the log_autoremove option in a way compatible with <v4.7 |
… | |
… | |
528 | Example: check wether version is strictly less then v4.7. |
521 | Example: check wether version is strictly less then v4.7. |
529 | |
522 | |
530 | BDB::VERSION v0, v4.7 |
523 | BDB::VERSION v0, v4.7 |
531 | or die "version 4.7 is not yet supported"; |
524 | or die "version 4.7 is not yet supported"; |
532 | |
525 | |
533 | CONTROLLING THE NUMBER OF THREADS |
526 | CONTROLLING THE NUMBER OF THREADS |
534 | BDB::min_parallel $nthreads |
527 | BDB::min_parallel $nthreads |
535 | Set the minimum number of BDB threads to $nthreads. The current |
528 | Set the minimum number of BDB threads to $nthreads. The current |
536 | default is 8, which means eight asynchronous operations can execute |
529 | default is 8, which means eight asynchronous operations can execute |
537 | concurrently at any one time (the number of outstanding requests, |
530 | concurrently at any one time (the number of outstanding requests, |
538 | however, is unlimited). |
531 | however, is unlimited). |
… | |
… | |
597 | You can still queue as many requests as you want. Therefore, |
590 | You can still queue as many requests as you want. Therefore, |
598 | "max_oustsanding" is mainly useful in simple scripts (with low |
591 | "max_oustsanding" is mainly useful in simple scripts (with low |
599 | values) or as a stop gap to shield against fatal memory overflow |
592 | values) or as a stop gap to shield against fatal memory overflow |
600 | (with large values). |
593 | (with large values). |
601 | |
594 | |
602 | BDB::set_sync_prepare $cb |
595 | $old_cb = BDB::set_sync_prepare $cb |
603 | Sets a callback that is called whenever a request is created without |
596 | Sets a callback that is called whenever a request is created without |
604 | an explicit callback. It has to return two code references. The |
597 | an explicit callback. It has to return two code references. The |
605 | first is used as the request callback (it should save the return |
598 | first is used as the request callback (it should save the return |
606 | status), and the second is called to wait until the first callback |
599 | status), and the second is called to wait until the first callback |
607 | has been called (it must set $! to the return status). |
600 | has been called (it must set $! to the return status). |
608 | |
601 | |
609 | This mechanism can be used to include BDB into other event |
602 | This mechanism can be used to include BDB into other event |
610 | mechanisms, such as AnyEvent::BDB or Coro::BDB. |
603 | mechanisms, such as Coro::BDB. |
611 | |
604 | |
612 | The default implementation works like this: |
605 | To allow other, callback-based, events to be executed while |
|
|
606 | callback-less ones are run, you could use this sync prepare |
|
|
607 | function: |
613 | |
608 | |
614 | sub { |
609 | sub { |
615 | my $status; |
610 | my $status; |
616 | ( |
611 | ( |
617 | sub { $status = $! }, |
612 | sub { $status = $! }, |
618 | sub { BDB::poll while !defined $status; $! = $status }, |
613 | sub { BDB::poll while !defined $status; $! = $status }, |
619 | ) |
614 | ) |
620 | } |
615 | } |
621 | |
616 | |
622 | It simply blocks the process till the request has finished and then |
617 | It works by polling for results till the request has finished and |
623 | sets $! to the return value. This means that if you don't use a |
618 | then sets $! to the return value. This means that if you don't use a |
624 | callback, BDB will simply fall back to synchronous operations. |
619 | callback, BDB would simply fall back to synchronous operations. |
625 | |
620 | |
|
|
621 | By default, or if the sync prepare function is set to "undef", is to |
|
|
622 | execute callback-less BDB requests in the foreground thread, setting |
|
|
623 | $! to the return value, without polling for other events. |
|
|
624 | |
626 | STATISTICAL INFORMATION |
625 | STATISTICAL INFORMATION |
627 | BDB::nreqs |
626 | BDB::nreqs |
628 | Returns the number of requests currently in the ready, execute or |
627 | Returns the number of requests currently in the ready, execute or |
629 | pending states (i.e. for which their callback has not been invoked |
628 | pending states (i.e. for which their callback has not been invoked |
630 | yet). |
629 | yet). |
631 | |
630 | |
… | |
… | |
640 | |
639 | |
641 | BDB::npending |
640 | BDB::npending |
642 | Returns the number of requests currently in the pending state |
641 | Returns the number of requests currently in the pending state |
643 | (executed, but not yet processed by poll_cb). |
642 | (executed, but not yet processed by poll_cb). |
644 | |
643 | |
|
|
644 | COMMON PITFALLS |
|
|
645 | Unexpected Crashes |
|
|
646 | Remember that, by default, BDB will execute requests in parallel, in |
|
|
647 | somewhat random order. That means that it is easy to run a "db_get" |
|
|
648 | request on thesa me database as a concurrent "db_close" request, leading |
|
|
649 | to a crash, silent data corruption, eventually the next world war on |
|
|
650 | terrorism. |
|
|
651 | |
|
|
652 | If you only ever use foreground requests (without a callback), this will |
|
|
653 | not be an issue. |
|
|
654 | |
|
|
655 | Unexpected Freezes or Deadlocks |
|
|
656 | Remember that, by default, BDB will execute requests in parallel, which |
|
|
657 | easily leads to deadlocks (even concurrent put's on the same database |
|
|
658 | can deadlock). |
|
|
659 | |
|
|
660 | You either need to run deadlock detection (and handle the resulting |
|
|
661 | errors), or make sure only one process ever updates the database, ine |
|
|
662 | one thread, e.g. by using only foreground requests (without a callback). |
|
|
663 | |
645 | FORK BEHAVIOUR |
664 | FORK BEHAVIOUR |
646 | This module should do "the right thing" when the process using it forks: |
665 | This module should do "the right thing" when the process using it forks: |
647 | |
666 | |
648 | Before the fork, BDB enters a quiescent state where no requests can be |
667 | Before the fork, BDB enters a quiescent state where no requests can be |
649 | added in other threads and no results will be processed. After the fork |
668 | added in other threads and no results will be processed. After the fork |
650 | the parent simply leaves the quiescent state and continues |
669 | the parent simply leaves the quiescent state and continues |
… | |
… | |
659 | |
678 | |
660 | Win32 note: there is no fork on win32, and perls emulation of it is too |
679 | Win32 note: there is no fork on win32, and perls emulation of it is too |
661 | broken to be supported, so do not use BDB in a windows pseudo-fork, |
680 | broken to be supported, so do not use BDB in a windows pseudo-fork, |
662 | better yet, switch to a more capable platform. |
681 | better yet, switch to a more capable platform. |
663 | |
682 | |
664 | MEMORY USAGE |
683 | MEMORY USAGE |
665 | Per-request usage: |
684 | Per-request usage: |
666 | |
685 | |
667 | Each aio request uses - depending on your architecture - around 100-200 |
686 | Each aio request uses - depending on your architecture - around 100-200 |
668 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
687 | bytes of memory. In addition, stat requests need a stat buffer (possibly |
669 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
688 | a few hundred bytes), readdir requires a result buffer and so on. Perl |
… | |
… | |
677 | |
696 | |
678 | In the execution phase, some aio requests require more memory for |
697 | In the execution phase, some aio requests require more memory for |
679 | temporary buffers, and each thread requires a stack and other data |
698 | temporary buffers, and each thread requires a stack and other data |
680 | structures (usually around 16k-128k, depending on the OS). |
699 | structures (usually around 16k-128k, depending on the OS). |
681 | |
700 | |
|
|
701 | WIN32 FILENAMES/DATABASE NAME MESS |
|
|
702 | Perl on Win32 supports only ASCII filenames (the reason is that it |
|
|
703 | abuses an internal flag to store wether a filename is Unicode or ANSI, |
|
|
704 | but that flag is used for somethign else in the perl core, so there is |
|
|
705 | no way to detect wether a filename is ANSI or Unicode-encoded). The BDB |
|
|
706 | module tries to work around this issue by assuming that the filename is |
|
|
707 | an ANSI filename and BDB was built for unicode support. |
|
|
708 | |
682 | KNOWN BUGS |
709 | KNOWN BUGS |
683 | Known bugs will be fixed in the next release, except: |
710 | Known bugs will be fixed in the next release, except: |
684 | |
711 | |
685 | If you use a transaction in any request, and the request returns |
712 | If you use a transaction in any request, and the request returns |
686 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |
713 | with an operating system error or DB_LOCK_NOTGRANTED, the internal |