| 1 |
=head1 NAME |
| 2 |
|
| 3 |
Coro::Mysql - let other threads run while doing mysql requests |
| 4 |
|
| 5 |
=head1 SYNOPSIS |
| 6 |
|
| 7 |
use Coro::Mysql; |
| 8 |
|
| 9 |
my $DBH = Coro::Mysql::unblock DBI->connect (...); |
| 10 |
|
| 11 |
=head1 DESCRIPTION |
| 12 |
|
| 13 |
(Note that in this manual, "thread" refers to real threads as implemented |
| 14 |
by the Coro module, not to the built-in windows process emulation which |
| 15 |
unfortunately is also called "threads") |
| 16 |
|
| 17 |
This module "patches" DBD::mysql database handles so that they do not |
| 18 |
block the whole process, but only the thread that they are used in. |
| 19 |
|
| 20 |
This can be used to make parallel sql requests using Coro, or to do other |
| 21 |
stuff while mysql is rumbling in the background. |
| 22 |
|
| 23 |
=head2 CAVEAT |
| 24 |
|
| 25 |
Note that this module must be linked against exactly the same |
| 26 |
F<libmysqlclient> library as DBD::mysql, otherwise it will not work. |
| 27 |
|
| 28 |
Also, while this module makes database handles non-blocking, you still |
| 29 |
cannot run multiple requests in parallel on the same database handle. If |
| 30 |
you want to run multiple queries in parallel, you have to create multiple |
| 31 |
database connections, one for each thread that runs queries. |
| 32 |
|
| 33 |
If you make sure that you never run two or more requests in parallel, you |
| 34 |
cna freely share the database handles between threads, of course. |
| 35 |
|
| 36 |
Also, this module uses a number of "unclean" techniques (patching an |
| 37 |
internal libmysql structure for one thing) and was hacked within a few |
| 38 |
hours on a long flight to Malaysia. |
| 39 |
|
| 40 |
It does, however, check whether it indeed got the structure layout |
| 41 |
correct, so you should expect perl exceptions or early crashes as opposed |
| 42 |
to data corruption when something goes wrong. |
| 43 |
|
| 44 |
=head2 SPEED |
| 45 |
|
| 46 |
This module is implemented in XS, and as long as mysqld replies quickly |
| 47 |
enough, it adds no overhead to the standard libmysql communication |
| 48 |
routines (which are very badly written). |
| 49 |
|
| 50 |
For very fast queries ("select 0"), this module can add noticable overhead |
| 51 |
(around 15%) as it tries to switch to other coroutines when mysqld doesn't |
| 52 |
deliver the data instantly. |
| 53 |
|
| 54 |
For most types of queries, there will be no overhead, especially on |
| 55 |
multicore systems where your perl process can do other things while mysqld |
| 56 |
does its stuff. |
| 57 |
|
| 58 |
=over 4 |
| 59 |
|
| 60 |
=cut |
| 61 |
|
| 62 |
package Coro::Mysql; |
| 63 |
|
| 64 |
use strict qw(vars subs); |
| 65 |
no warnings; |
| 66 |
|
| 67 |
use Scalar::Util (); |
| 68 |
use Carp qw(croak); |
| 69 |
|
| 70 |
use Guard; |
| 71 |
use Coro::Handle (); |
| 72 |
|
| 73 |
# we need this extra indirection, as Coro doesn't support |
| 74 |
# calling SLF-like functions via call_sv. |
| 75 |
|
| 76 |
sub readable { &Coro::Handle::FH::readable } |
| 77 |
sub writable { &Coro::Handle::FH::writable } |
| 78 |
|
| 79 |
BEGIN { |
| 80 |
our $VERSION = '0.2'; |
| 81 |
|
| 82 |
require XSLoader; |
| 83 |
XSLoader::load Coro::Mysql::, $VERSION; |
| 84 |
} |
| 85 |
|
| 86 |
=item $DBH = Coro::Mysql::unblock $DBH |
| 87 |
|
| 88 |
This function takes a DBI database handles and "patches" it |
| 89 |
so it becomes compatible to Coro threads. |
| 90 |
|
| 91 |
After that, it returns the patched handle - you should always use the |
| 92 |
newly returned database handle. |
| 93 |
|
| 94 |
It is safe to call this function on any database handle, but it will only |
| 95 |
do anything to L<DBD::mysql> handles, others are returned unchanged. |
| 96 |
|
| 97 |
=cut |
| 98 |
|
| 99 |
sub unblock { |
| 100 |
my ($DBH) = @_; |
| 101 |
|
| 102 |
if ($DBH->{Driver}{Name} eq "mysql") { |
| 103 |
my $sock = $DBH->{sock}; |
| 104 |
|
| 105 |
open my $fh, "+>&" . $DBH->{sockfd} |
| 106 |
or croak "Coro::Mysql unable to clone mysql fd"; |
| 107 |
|
| 108 |
$fh = Coro::Handle::unblock $fh; |
| 109 |
|
| 110 |
_patch $sock, $DBH->{sockfd}, tied ${$fh}; |
| 111 |
$DBH->{private_Coro_Mysql} = guard { |
| 112 |
_unpatch $sock; |
| 113 |
undef $fh; |
| 114 |
}; |
| 115 |
} |
| 116 |
|
| 117 |
$DBH |
| 118 |
} |
| 119 |
|
| 120 |
1; |
| 121 |
|
| 122 |
=back |
| 123 |
|
| 124 |
=head1 AUTHOR |
| 125 |
|
| 126 |
Marc Lehmann <schmorp@schmorp.de> |
| 127 |
http://home.schmorp.de/ |
| 128 |
|
| 129 |
=cut |
| 130 |
|
