Question

我使用这篇文章：http://www.perlmonks.org/?node_id=594175编写代码，将DBI与fork结合起来。它适用于Linux，但不适用于Windows XP。我使用的是Active状态Perl v5.10.0 MSWin32-x86-multi-thread，DBD :: mysql v4.011。

在Linux Perl v5.16.1上运行i486-linux-thread-multi DBD :: mysql v4.021。

代码。 dbi_fork.pl：

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
require "mysql.pl";

my $dbh = connect_mysql();

if (fork()) {
    $dbh->do("UPDATE articles SET title='parent' WHERE id=1");
}
else {
    my $dbh_child = $dbh->clone();
    $dbh->{InactiveDestroy} = 1;
    undef $dbh;
    $dbh_child->do("UPDATE articles SET title='child' WHERE id=2");
}

mysql.pl：

sub connect_mysql
{
    my $user_db = 'user';
    my $password_db = 'secret';
    my $base_name = 'test';
    my $mysql_host_url = 'localhost';

    my $dsn = "DBI:mysql:$base_name:$mysql_host_url";
    my $dbh = DBI->connect($dsn, $user_db, $password_db) or die $DBI::errstr;

    return $dbh;
}

1;

文章表：

DROP TABLE IF EXISTS `articles`;
CREATE TABLE `articles` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `title` varchar(50) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of articles
-- ----------------------------
INSERT INTO `articles` VALUES ('1', 'title1');
INSERT INTO `articles` VALUES ('2', 'title2');

在Windows上，它会出错：

$ perl ./dbi_fork.pl
DBD::mysql::db clone failed: handle 2 is owned by thread 2344b4 not current
thread 1a45014 (handles can't be shared between threads and your driver may
need a CLONE method added) at ./dbi_fork.pl line 14.

如何解决？

Answer 1

Windows上没有fork这样的东西。这是unix系统特有的功能。 Perl使用Windows上的线程模拟它，这会导致问题。

不要尝试重新创建现有连接，只需在任务中创建连接。

换句话说，使用

if (fork()) {
    my $dbh = connect_mysql();
    $dbh->do(...);
} else {
    my $dbh = connect_mysql();
    $dbh->do(...);
}

Answer 2

这是解决方案 - 每个线程都创建自己的连接：

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
require "mysql.pl";

if (fork()) {
    my $dbh = connect_mysql();
    $dbh->do("UPDATE articles SET title='parent' WHERE id=1");
}
else {
    my $dbh = connect_mysql();
    $dbh->do("UPDATE articles SET title='child' WHERE id=2");
}

DBI和fork在Windows上不起作用

2 个答案: