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Comparing BDB/BDB.pm (file contents):
Revision 1.16 by root, Sun Sep 16 18:17:58 2007 UTC vs.
Revision 1.19 by root, Wed Dec 5 13:01:46 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 = '1.1'; 112 our $VERSION = '1.2';
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
435interactiveness when perl is not fast enough to process all requests in 470interactiveness when perl is not fast enough to process all requests in
436time. 471time.
437 472
438For interactive programs, values such as C<0.01> to C<0.1> should be fine. 473For interactive programs, values such as C<0.01> to C<0.1> should be fine.
439 474
440Example: Install an Event watcher that automatically calls 475Example: Install an EV watcher that automatically calls
441BDB::poll_cb with low priority, to ensure that other parts of the 476BDB::poll_cb with low priority, to ensure that other parts of the
442program get the CPU sometimes even under high AIO load. 477program get the CPU sometimes even under high load.
443 478
444 # try not to spend much more than 0.1s in poll_cb 479 # try not to spend much more than 0.1s in poll_cb
445 BDB::max_poll_time 0.1; 480 BDB::max_poll_time 0.1;
446 481
447 # use a low priority so other tasks have priority 482 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);
451 483
452=item BDB::poll_wait 484=item BDB::poll_wait
453 485
454If there are any outstanding requests and none of them in the result 486If there are any outstanding requests and none of them in the result
455phase, wait till the result filehandle becomes ready for reading (simply 487phase, wait till the result filehandle becomes ready for reading (simply
467 499
468 BDB::poll_wait, BDB::poll_cb 500 BDB::poll_wait, BDB::poll_cb
469 501
470=item BDB::flush 502=item BDB::flush
471 503
472Wait till all outstanding AIO requests have been handled. 504Wait till all outstanding BDB requests have been handled.
473 505
474Strictly equivalent to: 506Strictly equivalent to:
475 507
476 BDB::poll_wait, BDB::poll_cb 508 BDB::poll_wait, BDB::poll_cb
477 while BDB::nreqs; 509 while BDB::nreqs;
482 514
483=over 4 515=over 4
484 516
485=item BDB::min_parallel $nthreads 517=item BDB::min_parallel $nthreads
486 518
487Set the minimum number of AIO threads to C<$nthreads>. The current 519Set the minimum number of BDB threads to C<$nthreads>. The current
488default is C<8>, which means eight asynchronous operations can execute 520default is C<8>, which means eight asynchronous operations can execute
489concurrently at any one time (the number of outstanding requests, 521concurrently at any one time (the number of outstanding requests,
490however, is unlimited). 522however, is unlimited).
491 523
492BDB starts threads only on demand, when an AIO request is queued and 524BDB 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 525no 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 526create 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. 527is in the cache and could have been processed faster by a single thread.
496 528
497It is recommended to keep the number of threads relatively low, as some 529It 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 534Under most circumstances you don't need to call this function, as the
503module selects a default that is suitable for low to moderate load. 535module selects a default that is suitable for low to moderate load.
504 536
505=item BDB::max_parallel $nthreads 537=item BDB::max_parallel $nthreads
506 538
507Sets the maximum number of AIO threads to C<$nthreads>. If more than the 539Sets the maximum number of BDB threads to C<$nthreads>. If more than the
508specified number of threads are currently running, this function kills 540specified number of threads are currently running, this function kills
509them. This function blocks until the limit is reached. 541them. This function blocks until the limit is reached.
510 542
511While C<$nthreads> are zero, aio requests get queued but not executed 543While C<$nthreads> are zero, aio requests get queued but not executed
512until the number of threads has been increased again. 544until the number of threads has been increased again.
615 647
616=head2 FORK BEHAVIOUR 648=head2 FORK BEHAVIOUR
617 649
618This module should do "the right thing" when the process using it forks: 650This module should do "the right thing" when the process using it forks:
619 651
620Before the fork, IO::AIO enters a quiescent state where no requests 652Before the fork, BDB enters a quiescent state where no requests
621can be added in other threads and no results will be processed. After 653can be added in other threads and no results will be processed. After
622the fork the parent simply leaves the quiescent state and continues 654the fork the parent simply leaves the quiescent state and continues
623request/result processing, while the child frees the request/result queue 655request/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 656(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 657parent). Threads will be started on demand until the limit set in the
626parent process has been reached again. 658parent process has been reached again.
627 659
628In short: the parent will, after a short pause, continue as if fork had 660In 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 661not been called, while the child will act as if BDB has not been used
630yet. 662yet.
631 663
632=head2 MEMORY USAGE 664=head2 MEMORY USAGE
633 665
634Per-request usage: 666Per-request usage:
657 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>, 689 TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
658 above. 690 above.
659 691
660=head1 SEE ALSO 692=head1 SEE ALSO
661 693
662L<Coro::AIO>. 694L<Coro::BDB>, L<IO::AIO>.
663 695
664=head1 AUTHOR 696=head1 AUTHOR
665 697
666 Marc Lehmann <schmorp@schmorp.de> 698 Marc Lehmann <schmorp@schmorp.de>
667 http://home.schmorp.de/ 699 http://home.schmorp.de/

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