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Manual Reference Pages  -  KAFKA::MESSAGE (3)

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NAME

Kafka::Message - Interface to the Kafka message properties.

CONTENTS

VERSION

This documentation refers to Kafka::Message version 0.8010 .

SYNOPSIS



    use 5.010;
    use strict;
    use warnings;

    use Kafka qw(
        $DEFAULT_MAX_BYTES
    );
    use Kafka::Connection;
    use Kafka::Consumer;

    #-- Connection
    my $connection = Kafka::Connection->new( host => localhost );

    #-- Consumer
    my $consumer = Kafka::Consumer->new( Connection  => $connection );

    # The Kafka consumer response has an ARRAY reference type.
    # For the fetch response array has the class name Kafka::Message elements.

    # Consuming messages
    my $messages = $consumer->fetch(
        mytopic,          # topic
        0,                  # partition
        0,                  # offset
        $DEFAULT_MAX_BYTES  # Maximum size of MESSAGE(s) to receive
    );
    if ( $messages ) {
        foreach my $message ( @$messages ) {
            if( $message->valid ) {
                say key        : , $message->key;
                say payload    : , $message->payload;
                say offset     : , $message->offset;
                say next_offset: , $message->next_offset;
            } else {
                say error      : , $message->error;
            }
        }
    }

    # Closes and cleans up
    undef $consumer;
    undef $connection;



DESCRIPTION

This module is not intended to be used by the end user.

Kafka::Message class implements API for Kafka message.

fetch method of the Consumer client returns reference to an array of objects of this class.

The main features of the Kafka::Message class are:
o Represents Apache Kafka Message structure. Description of the structure is available at <https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-Messagesets>

    CONSTRUCTOR

new ( \%arg )

Creates a new Kafka::Message object. new() takes an argument - HASH reference with the message attributes corresponding to accessors.

    METHODS

payload

A simple message received from the Apache Kafka server.

key

The key is an optional message key that was used for partition assignment. The key can be an empty string.

valid

Boolean value: indicates whether received message is valid or not.

error

A description why message is invalid.

offset

The offset of the message in the Apache Kafka server.

next_offset

The offset of the next message in the Apache Kafka server.

Attributes

This holds metadata attributes about the message. The lowest 2 bits contain the compression codec used for the message. The other bits are currently unused.

HighwaterMarkOffset

The offset at the end of the log for this partition. This can be used by the client to determine how many messages behind the end of the log they are.

MagicByte

This is version id used to allow backwards compatible evolution of the message binary format.

DIAGNOSTICS

In order to achieve better performance, constructor of this module does not perform validation of arguments.

SEE ALSO

The basic operation of the Kafka package modules:

Kafka - constants and messages used by the Kafka package modules.

Kafka::Connection - interface to connect to a Kafka cluster.

Kafka::Producer - interface for producing client.

Kafka::Consumer - interface for consuming client.

Kafka::Message - interface to access Kafka message properties.

Kafka::Int64 - functions to work with 64 bit elements of the protocol on 32 bit systems.

Kafka::Protocol - functions to process messages in the Apache Kafka’s Protocol.

Kafka::IO - low-level interface for communication with Kafka server.

Kafka::Exceptions - module designated to handle Kafka exceptions.

Kafka::Internals - internal constants and functions used by several package modules.

A wealth of detail about the Apache Kafka and the Kafka Protocol:

Main page at <http://kafka.apache.org/>

Kafka Protocol at <https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol>

SOURCE CODE

Kafka package is hosted on GitHub: <https://github.com/TrackingSoft/Kafka>

AUTHOR

Sergey Gladkov, <sgladkov@trackingsoft.com>

CONTRIBUTORS

Alexander Solovey

Jeremy Jordan

Sergiy Zuban

Vlad Marchenko

COPYRIGHT AND LICENSE

Copyright (C) 2012-2013 by TrackingSoft LLC.

This package is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic at <http://dev.perl.org/licenses/artistic.html>.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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