Question

I am having problem with calling both Parallel::ForkManager and Inline::Java at the same time. Specifically, if I call the Inline::Java with the JNI => 1 option (which I have to), then the fork process doesn’t come back to the parent. Here are the codes:

use Parallel::ForkManager;

##### Calling Inline::Java #####
use Inline Java => <<END, JNI => 1;

END
###### End of Inline::Java #####

my $pm = Parallel::ForkManager->new(2);
for my $i (0..1) {
    $pm->start and next;
    print "Inside process $i\n";
    $pm->finish;
}
$pm->wait_all_children;
print "Back to Parent.\n";

If I run this program, it goes into the child processes but never comes back to the parent. If I remove the 3 lines between the comments, it runs fine. If I change the JNI => 1 to JNI => 0 (not that I’m allowed to change that parameter for my purpose), then there is an error message of Lost connection with Java virtual machine at /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi/Inline/Java.pm line 975.

Does anyone have a clue how to resolve the conflict? I also have to call the Inline::Java before the parallel process so using require after parallel is done is not an option. Thx!

Answer 1

Every child is talking over the same socket, which leads to the VM receiving jibberish.

You need to delay making a connection to the VM so that it’s done in the children instead of it the parent.

You could move all thing Inline::Java-related into another module, then use require Child; (not use Child;) after start.

If you need to use Inline::Java before launching the child, do it in a different process.