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Comparing BDB/BDB.pm (file contents):
Revision 1.17 by root, Tue Dec 4 10:13:50 2007 UTC vs.
Revision 1.22 by root, Mon Dec 10 03:57:27 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 # automatic result processing with AnyEvent:
30 our $FH; open $FH, "<&=" . BDB::poll_fileno;
31 our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
32
33 # automatic result processing with EV:
34 my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
35
36 # with Glib:
37 add_watch Glib::IO BDB::poll_fileno,
38 in => sub { BDB::poll_cb; 1 };
39
40 # or simply flush manually
41 BDB::flush;
42
8 43
9=head1 DESCRIPTION 44=head1 DESCRIPTION
10 45
11See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>). 46See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12The BDB API is very similar to the C API (the translation has been very faithful). 47The BDB API is very similar to the C API (the translation has been very faithful).
72use strict 'vars'; 107use strict 'vars';
73 108
74use base 'Exporter'; 109use base 'Exporter';
75 110
76BEGIN { 111BEGIN {
77 our $VERSION = '1.2'; 112 our $VERSION = '1.3';
78 113
79 our @BDB_REQ = qw( 114 our @BDB_REQ = qw(
80 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect 115 db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
81 db_env_memp_sync db_env_memp_trickle 116 db_env_memp_sync db_env_memp_trickle
82 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range 117 db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range
99 134
100=head2 BERKELEYDB FUNCTIONS 135=head2 BERKELEYDB FUNCTIONS
101 136
102All of these are functions. The create functions simply return a new 137All of these are functions. The create functions simply return a new
103object and never block. All the remaining functions all take an optional 138object and never block. All the remaining functions all take an optional
104callback as last argument. If it is missing, then the fucntion will be 139callback as last argument that gets passed the return value. If it is
105executed synchronously. 140missing, then the function will be executed synchronously, and the return
141value is returned as normally.
106 142
107BDB functions that cannot block (mostly functions that manipulate 143BDB functions that cannot block (mostly functions that manipulate
108settings) are method calls on the relevant objects, so the rule of thumb 144settings) 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 145is: if its a method, its not blocking, if its a function, it takes a
110callback as last argument. 146callback as last argument.
242 $int = $env->set_lk_max_lockers (U32 max) 278 $int = $env->set_lk_max_lockers (U32 max)
243 $int = $env->set_lk_max_locks (U32 max) 279 $int = $env->set_lk_max_locks (U32 max)
244 $int = $env->set_lk_max_objects (U32 max) 280 $int = $env->set_lk_max_objects (U32 max)
245 $int = $env->set_lg_bsize (U32 max) 281 $int = $env->set_lg_bsize (U32 max)
246 $int = $env->set_lg_max (U32 max) 282 $int = $env->set_lg_max (U32 max)
283 $int = $env->mutex_set_increment (U32 increment)
284 $int = $env->mutex_set_tas_spins (U32 tas_spins)
285 $int = $env->mutex_set_max (U32 max)
286 $int = $env->mutex_set_align (U32 align)
247 287
248 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0) 288 $txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
249 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC 289 flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
250 290
251=head4 Example: 291=head4 Example:
435interactiveness when perl is not fast enough to process all requests in 475interactiveness when perl is not fast enough to process all requests in
436time. 476time.
437 477
438For interactive programs, values such as C<0.01> to C<0.1> should be fine. 478For interactive programs, values such as C<0.01> to C<0.1> should be fine.
439 479
440Example: Install an Event watcher that automatically calls 480Example: Install an EV watcher that automatically calls
441BDB::poll_cb with low priority, to ensure that other parts of the 481BDB::poll_cb with low priority, to ensure that other parts of the
442program get the CPU sometimes even under high AIO load. 482program get the CPU sometimes even under high load.
443 483
444 # try not to spend much more than 0.1s in poll_cb 484 # try not to spend much more than 0.1s in poll_cb
445 BDB::max_poll_time 0.1; 485 BDB::max_poll_time 0.1;
446 486
447 # use a low priority so other tasks have priority 487 my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
448 Event->io (fd => BDB::poll_fileno,
449 poll => 'r', nice => 1,
450 cb => &BDB::poll_cb);
451 488
452=item BDB::poll_wait 489=item BDB::poll_wait
453 490
454If there are any outstanding requests and none of them in the result 491If there are any outstanding requests and none of them in the result
455phase, wait till the result filehandle becomes ready for reading (simply 492phase, wait till the result filehandle becomes ready for reading (simply
467 504
468 BDB::poll_wait, BDB::poll_cb 505 BDB::poll_wait, BDB::poll_cb
469 506
470=item BDB::flush 507=item BDB::flush
471 508
472Wait till all outstanding AIO requests have been handled. 509Wait till all outstanding BDB requests have been handled.
473 510
474Strictly equivalent to: 511Strictly equivalent to:
475 512
476 BDB::poll_wait, BDB::poll_cb 513 BDB::poll_wait, BDB::poll_cb
477 while BDB::nreqs; 514 while BDB::nreqs;
482 519
483=over 4 520=over 4
484 521
485=item BDB::min_parallel $nthreads 522=item BDB::min_parallel $nthreads
486 523
487Set the minimum number of AIO threads to C<$nthreads>. The current 524Set the minimum number of BDB threads to C<$nthreads>. The current
488default is C<8>, which means eight asynchronous operations can execute 525default is C<8>, which means eight asynchronous operations can execute
489concurrently at any one time (the number of outstanding requests, 526concurrently at any one time (the number of outstanding requests,
490however, is unlimited). 527however, is unlimited).
491 528
492BDB starts threads only on demand, when an AIO request is queued and 529BDB starts threads only on demand, when an BDB request is queued and
493no free thread exists. Please note that queueing up a hundred requests can 530no free thread exists. Please note that queueing up a hundred requests can
494create demand for a hundred threads, even if it turns out that everything 531create demand for a hundred threads, even if it turns out that everything
495is in the cache and could have been processed faster by a single thread. 532is in the cache and could have been processed faster by a single thread.
496 533
497It is recommended to keep the number of threads relatively low, as some 534It is recommended to keep the number of threads relatively low, as some
502Under most circumstances you don't need to call this function, as the 539Under most circumstances you don't need to call this function, as the
503module selects a default that is suitable for low to moderate load. 540module selects a default that is suitable for low to moderate load.
504 541
505=item BDB::max_parallel $nthreads 542=item BDB::max_parallel $nthreads
506 543
507Sets the maximum number of AIO threads to C<$nthreads>. If more than the 544Sets the maximum number of BDB threads to C<$nthreads>. If more than the
508specified number of threads are currently running, this function kills 545specified number of threads are currently running, this function kills
509them. This function blocks until the limit is reached. 546them. This function blocks until the limit is reached.
510 547
511While C<$nthreads> are zero, aio requests get queued but not executed 548While C<$nthreads> are zero, aio requests get queued but not executed
512until the number of threads has been increased again. 549until the number of threads has been increased again.
615 652
616=head2 FORK BEHAVIOUR 653=head2 FORK BEHAVIOUR
617 654
618This module should do "the right thing" when the process using it forks: 655This module should do "the right thing" when the process using it forks:
619 656
620Before the fork, IO::AIO enters a quiescent state where no requests 657Before the fork, BDB enters a quiescent state where no requests
621can be added in other threads and no results will be processed. After 658can be added in other threads and no results will be processed. After
622the fork the parent simply leaves the quiescent state and continues 659the fork the parent simply leaves the quiescent state and continues
623request/result processing, while the child frees the request/result queue 660request/result processing, while the child frees the request/result queue
624(so that the requests started before the fork will only be handled in the 661(so that the requests started before the fork will only be handled in the
625parent). Threads will be started on demand until the limit set in the 662parent). Threads will be started on demand until the limit set in the
626parent process has been reached again. 663parent process has been reached again.
627 664
628In short: the parent will, after a short pause, continue as if fork had 665In short: the parent will, after a short pause, continue as if fork had
629not been called, while the child will act as if IO::AIO has not been used 666not been called, while the child will act as if BDB has not been used
630yet. 667yet.
631 668
632=head2 MEMORY USAGE 669=head2 MEMORY USAGE
633 670
634Per-request usage: 671Per-request usage:
657 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 694 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
658 above. 695 above.
659 696
660=head1 SEE ALSO 697=head1 SEE ALSO
661 698
662L<Coro::AIO>. 699L<Coro::BDB>, L<IO::AIO>.
663 700
664=head1 AUTHOR 701=head1 AUTHOR
665 702
666 Marc Lehmann <schmorp@schmorp.de> 703 Marc Lehmann <schmorp@schmorp.de>
667 http://home.schmorp.de/ 704 http://home.schmorp.de/

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