I have a requirement to connect to a Kafka server over SSL. I have the certs, private key, and password, but I can't work out how to even test a connection. Looking at the Kafka modules, they use Socket to create the connection, and the Kafka modules don't support SSL.

I've started playing with IO::Socket::SSL to try to connect to the server, but I think I'll have to work out how to do this at the lower level Socket interface, even if I manage to connect using IO::Socket::SSL, because of how Kafka::IO is written. I know very little about socket coding, nor why the decision was made to use Socket over IO::Socket so this feels like a very steep learning curve. So far, I've managed to create the socket, and I can send data to the server, but I'm guessing the server thinks it's just gibberish, because it closes the socket straight away. Or, possibly, I'm not doing whatever it is I need to do with the password to get a valid response.

Does anyone have any pointers that could get me going in the right direction. I did drag out my old copy of Stein's Network programming with Perl, but I don't see any references to SSL in it.

I get no errors when running this at debug level 3:

my $socket = IO::Socket::SSL->new(
    PeerAddr        => $host,
    PeerPort        => 9094,
    SSL_verify_mode => SSL_VERIFY_NONE,
    SSL_key_file    => './key.pem',
    SSL_cert_file   => './cert.pem',
) or die "failed to connect: $SSL_ERROR"
[download]

but that doesn't include using the password (I'm not sure whether that's for the SSL level or Kafka level ATM). Is there something I can print to the socket to get metadata from the server?

I tried looking for info on the raw socket commends that Kafka uses, but I'm only finding API docs right now :/

All pointers welcomed...

update

Got it working with Net::Kafka after following the pointers below. For future reference for those that need it, here's the code I used:

use v5.22;
use strictures 2;
use JSON::XS qw(decode_json);
use Data::Dumper 'Dumper';

use Net::Kafka::Consumer;

my $consumer    = Net::Kafka::Consumer->new(
  'bootstrap.servers'     => 'server1.com:9094,server2.com:9094,server
+3.com:9094',
  'group.id'              => 'my_consumer_group',
  'security.protocol'     => 'SSL',
  'ssl.keystore.location' => '/path/to/kafka.client.keystore.p12',
  'ssl.keystore.password' => 'password',
  'ssl.key.password'      => 'password',
  error_cb                => sub {
    my ($self, $err, $msg) = @_;
    warn Dumper({ ERR => $err, MSG => $msg });
  },
);

# see https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION
+.md for all options

$consumer->subscribe( [ "my_topic" ] );
warn Dumper({ consumer => $consumer });

while (1) {
  my $msg = $consumer->poll(1000);
  if ($msg) {
    if ( my $err = $msg->err ) {
      say "Error: ", Net::Kafka::Error::to_string($err);
    }
    else {
      say Dumper({ PAYLOAD => decode_json $msg->payload });
    }
  }
}
[download]

The module is sparsely documented, so I ended up doing a little hit and miss testing to get here.

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