[rabbitmq-discuss] Perl Net::RabbitMQ and failure conditions

Thu May 19 21:44:59 BST 2011

I'm trying to understand how RabbitMQ behaves under failure conditions,
specifically when using the Net::RabbitMQ Perl module.

We have RabbitMQ set up with three nodes, one on the backend, which holds
the actual queues, and two on the frontend, which receive publish requests.

RabbitMQ 2.2.0
Net::RabbitMQ 0.1.8

Below is the chart of behaviors that I have observed.

"+" means the behavior is as I expected: either the message is successfully
queued, or an error is thrown.
"-" means the behavior is not as I expected, but can be managed:
specifically, the process receives a SIGPIPE, which I can trap and recover
from.
"!" means the behavior is not as I expected, and cannot be managed: the
message is not queued but no error is thrown and/or the process hangs.

"App down" means I ran `rabbitmqctl stop_app`.  "Daemon down" means I ran
`rabbitmqctl stop`.

  As publishing process starts up:

    Remote daemon up, app up
      + Everything okay

    Remote daemon up, app down
      ! Net::RabbitMQ hangs when declaring queue

    Remote daemon down
      + Net::RabbitMQ throws error when declaring queue
        "Declaring queue: server channel error 404, message: NOT_FOUND - no
queue 'test' in vhost '/'"

    Local daemon up, app down
      + Net::RabbitMQ throws error when connecting
        "Opening socket: Connection refused"

    Local daemon down
      + Net::RabbitMQ throws error when connecting
        "Opening socket: Connection refused"

  After publishing process starts up:

    Local app goes down
      - Process receives SIGPIPE

    Local daemon goes down
      - Process receives SIGPIPE

    Remote app goes down
      ! Net::RabbitMQ falsely indicates success when publishing, then hangs
(in DESTROY?)

    Remote daemon goes down
      ! Net::RabbitMQ falsely indicates success when publishing

    Local app goes down, comes back up
      - Process receives SIGPIPE

    Local daemon goes down, comes back up
      - Process receives SIGPIPE

    Remote app goes down, comes back up
      + Everything okay

    Remote daemon goes down, comes back up
      + Everything okay

Have other people had these problems with Net::RabbitMQ?  Can we resolve
these issues by changing something in our RabbitMQ configuration?

thanks,
Ronald

P.S. Here's my script.

#!/usr/local/bin/perl

use strict;
use warnings;

use Net::RabbitMQ;

$| = 1;

$SIG{'PIPE'} = sub { die "SIGPIPE\n" };

my $mq = Net::RabbitMQ->new();

alarm(10);

print "Connecting\n";
$mq->connect('localhost', { user => 'engagement', password => '********' })
  or die "Can't connect to RabbitMQ\n";

print "Opening channel\n";
$mq->channel_open(1);

print "Declaring exchange\n";
$mq->exchange_declare(1, 'ee_exchange', { durable => 1 });

print "Declaring queue\n";
$mq->queue_declare(1, 'test', { durable => 1 });

print "Binding queue\n";
$mq->queue_bind(1, 'test', 'ee_exchange', 'ee_test');

alarm(0);

print "> ";
<>;

alarm(10);

print "Publishing message\n";
my $rc =
  $mq->publish(1, 'ee_test', 'hello world!',
               { exchange => 'ee_exchange', mandatory => 1, immediate => 0
},
               { delivery_mode => 2 });
print "Result: $rc\n";

__END__
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