AnyEvent::STOMP::Client + AnyEvent::ForkManger = Intermittent Error - perl

Question

I'm trying to write a process that listens to ActiveMQ and based on the message, goes out and grabs data from a webservice, does some processing and then puts the process data to another webservice. (REST/JSON)
The module below works fine until one of the wonky webservices I talk to returns an error. I've tried many things to catch the error but to no avail, yet. Once the webservice error happens though I get the following message:
unhandled callback exception on event (MESSAGE,
AnyEvent::STOMP::Client=HASH(0x3ad5e48), HASH(0x3a6bbb0)
{"action":"created","data":{"id":40578737,"type":"alert","who":null},"guid":"ADCCEE0C-73A7-11E6-8084-74B346D1CA67","hostname":"myserver","pid":48632}):
$fork_manager->start() should be called within the manager process
OK, I conceptually understand that child process is trying to start another process and that fork manager is saying that is a no no. But given the module below, what is the proper way to start a new process to handle the long running processing. Or why is an child process dying causing this exception and how can I prevent this
Here's the module (stripped down)
package consumer;
use AnyEvent::ForkManager;
use AnyEvent::STOMP::Client;
use JSON;
use Data::Dumper;
use v5.18;
use Moose;
sub run {
my $self = shift;
my $pm = AnyEvent::ForkManager->new(max_workers => 20);
my $stomp = AnyEvent::STOMP::Client->new();
$stomp->connect();
$stomp->on_connected(sub {
my $stomp = shift;
$stomp->subscribe('/topic/test');
say "Connected to STOMP";
});
$pm->on_start(sub {
my ($pm,$pid,#params) = #_;
say "Starting $pid worker";
});
$pm->on_finish(sub {
my ($pm, $pid,#params) = #_;
say "Finished $pid worker";
});
$pm->on_error(sub {
say Dumper(\#_);
});
$stomp->on_message(sub {
my ($stomp, $header, $body) = #_;
my $href = decode_json $body;
$pm->start(cb => sub {
my ($pm, #params) = #_;
$self->process(#params);
},
args => [ $href->{id}, $href->{data}->{type}, $href->{data}->{who} ],
);
});
my $cv = AnyEvent->condvar;
$cv->recv;
}
sub process {
say "Processing ".Dumper(\#_);
sleep 5;
if ( int(rand(10)) < 5 ) {
die "OOPS"; # this triggers the error message above
}
say "Done Processing $_[1]";
}
1;
Heres the driver for the module above:
#!/usr/bin/env perl
use v5.18;
use lib '.';
use consumer;
my $c = consumer->new();
$c->run;
Finally a traffic generator that you can use to see this in action:
#!/usr/bin/env perl
use lib '../lib';
use lib '../../lib';
use v5.18;
use Data::Dumper;
use JSON;
use Net::STOMP::Client;
$ENV{'scot_mode'} = "testing";
my $stomp = Net::STOMP::Client->new(
host => "127.0.0.1",
port => 61613
);
$stomp->connect();
for (my $i = 1; $i < 1000000; $i++) {
my $href = {
id => $i,
type => "event",
what => "foo",
};
my $json = encode_json $href;
say "Sending ".Dumper($href);
$stomp->send(
destination => "/topic/test",
body => $json,
);
}
$stomp->disconnect();

Answer 1

I was able to solve this by using Try::Catch and wrapping the call to self->process with a try catch like this:
$stomp->on_message(sub {
my ($stomp, $header, $body) = #_;
my $href = decode_json $body;
$pm->start(cb => sub {
my ($pm, #params) = #_;
try {
$self->process(#params);
}
catch {
# error handling stuff
};
},
args => [ $href->{id}, $href->{data}->{type}, $href->{data}->{who} ],
);
}
);