Re^4: Why isn't this code thread-safe? (MCE!)

[marioroy]

Hi again,

Here is the same thing using MCE::Hobo. Similar code, but processes instead.

use warnings;
use feature 'say';
use MCE::Hobo;
use MCE::Shared;

# use IO::Handle;  # <-- loaded automatically by MCE and MCE::Shared::
+Server

my $q = MCE::Shared-> queue;

my @gang = map mce_async( sub {
    while ( defined( my $f = $q-> dequeue )) {
        require Compress::Zlib;
        say MCE::Hobo-> tid;
    }
}), 1 .. 100;

$q-> enqueue( $_ ) for 1 .. 100;
$q-> end;

$_-> join for @gang;

For modules not multi-process safe, another thing one can do on Unix platforms is having MCE::Hobo default to posix_exit to avoid all END and destructor processing.

use warnings;
use feature 'say';
use MCE::Hobo;
use MCE::Shared;

# use IO::Handle;  # <-- loaded automatically by MCE before spawning

MCE::Hobo->init( posix_exit => 1 );

my $q = MCE::Shared-> queue;

my @gang = map mce_async( sub {
    while ( defined( my $f = $q-> dequeue )) {
        require Compress::Zlib;
        say MCE::Hobo-> tid;
    }
}), 1 .. 8;

$q-> enqueue( $_ ) for 1 .. 8;
$q-> end;

$_-> join for @gang;

Note that the posix_exit option is not recommended if constructing an object inside the worker involving a temp file. In that case one may want the worker to exit normally. Anyway, the posix_exit option is there if needed as a last resort.

Taken from the MCE::Hobo manual: Set posix_exit to avoid all END and destructor processing. Constructing MCE::Hobo inside a thread implies 1 or if present CGI, FCGI, Coro, Curses, Gearman::Util, Gearman::XS, LWP::UserAgent, Mojo::IOLoop, Prima, STFL, Tk, Wx, or Win32::GUI.

A lot of modules are not multi-process safe and the reason for setting to 1 automatically. Btw, Prima is now multi-process safe recently.

Kind regards, Mario