Sergey Gladkov > Kafka-0.12 > Kafka::IO

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Module Version: 0.12   Source   Latest Release: Kafka-0.8008_1

NAME ^

Kafka::IO - object interface to socket communications with the Apache Kafka 0.7 server without using the Apache ZooKeeper

VERSION ^

This documentation refers to Kafka::IO version 0.12

SYNOPSIS ^

Setting up:

    use Kafka qw( KAFKA_SERVER_PORT DEFAULT_TIMEOUT );
    use Kafka::IO;

    my $io;

    eval { $io = Kafka::IO->new(
        host        => "localhost",
        port        => KAFKA_SERVER_PORT,
        timeout     => "bad thing",
        RaiseError  => 1
        ) };
    print "expecting to die: (",
        Kafka::IO::last_errorcode, ") ",
        Kafka::IO::last_error, "\n" if $@;

    unless ( $io = Kafka::IO->new(
        host        => "localhost",
        port        => KAFKA_SERVER_PORT,
        timeout     => DEFAULT_TIMEOUT, # Optional,
                                        # default = DEFAULT_TIMEOUT
        RaiseError  => 0                # Optional, default = 0
        ) )
    {
        print "unexpecting to die: (",
            Kafka::IO::last_errorcode, ") ",
            Kafka::IO::last_error, "\n" if $@;
    }

Producer:

    use Kafka::Producer;

    my $producer = Kafka::Producer->new(
        IO          => $io,
        RaiseError  => 0                # Optional, default = 0
        );

    # ... the application body

    # Closes the producer and cleans up
    $producer->close;

Or Consumer:

    use Kafka::Consumer;

    my $consumer = Kafka::Consumer->new(
        IO          => $io,
        RaiseError  => 0                # Optional, default = 0
        );

    # ... the application body

    # Closes the consumer and cleans up
    $consumer->close;

DESCRIPTION ^

The main features of the Kafka::IO class are:

CONSTRUCTOR

new

Establishes socket TCP connection on given host and port, creates a Kafka::IO IO object. Returns the created a Kafka::IO object.

An error will cause the program to halt or the constructor will return the undefined value, depending on the value of the RaiseError attribute.

You can use the methods of the Kafka::IO class - "last_errorcode" and "last_error" for the information about the error.

new() takes arguments in key-value pairs. The following arguments are currently recognized:

host => $host

$host is an Apache Kafka host to connect to. It can be a hostname or the IP-address in the "xx.xx.xx.xx" form.

port => $port

Optional, default = KAFKA_SERVER_PORT .

$port is the attribute denoting the port number of the service we want to access (Apache Kafka service). The $port should be a number.

KAFKA_SERVER_PORT is the default Apache Kafka server port = 9092.

timeout => $timeout

Optional, default = DEFAULT_TIMEOUT .

DEFAULT_TIMEOUT is the default timeout that can be imported from the Kafka module.

$timeout specifies how much time we give remote server to respond before the IO object disconnects and creates an internal exception. The $timeout in secs, for gethostbyname, connect, blocking receive and send calls (could be any integer or floating-point type).

The first connect will never fail with a timeout as the connect call will not block.

RaiseError => $mode

Optional, default = 0 .

An error will cause the program to halt if "RaiseError" is true: confess if the argument is not valid or die in the other error case. Returns the undefined value if "RaiseError" is not true and any error occured.

METHODS

The following methods are defined for the Kafka::IO class:

send( $message )

Sends a message on a Kafka::IO object socket. Reconnects on unconnected sockets.

The argument must be a bytes string.

Returns the number of characters sent. If there's an error, returns the undefined value if the "RaiseError" is not true.

receive( $length )

Receives a message on an IO object socket. Attempts to receive the $length bytes of data.

Returns a reference to the received message. If there's an error, returns the undefined value if the "RaiseError" is not true.

The argument must be a value that is a positive number. That is, it is defined and Perl thinks it's a number.

close

The method to close the Kafka::IO object and clean up.

last_errorcode

This method returns an error code that specifies the position of the description in the @Kafka::ERROR array. Analysing this information can be done to determine the cause of the error.

The server or the resource might not be available, access to the resource might be denied or other things might have failed for some reason.

Complies with an array of descriptions @Kafka::ERROR.

last_error

This method returns an error message that contains information about the encountered failure. Messages returned from this method may contain additional details and do not comply with the Kafka::ERROR array.

RaiseError

The method which causes the undefined value to be returned when an error is detected if "RaiseError" set to false, or to die automatically if "RaiseError" set to true (this can always be trapped with eval).

It must be a non-negative integer. That is, a positive integer, or zero.

You should always check for errors, when not establishing the "RaiseError" mode to true.

DIAGNOSTICS ^

Look at the RaiseError description for additional information on error handeling.

The methods for the possible error to analyse: "last_errorcode" and more descriptive "last_error".

Mismatch argument

This means that you didn't give the right argument to a new constructor or to other method.

Can't send

This means that the message can't be sent on a Kafka::IO object socket.

Can't recv

This means that the message can't be received on a Kafka::IO object socket.

Can't bind

This means that the socket TCP connection can't be established on on given host and port.

For more error description, always look at the message from "last_error" method or from Kafka::IO::last_error class method.

SEE ALSO ^

The basic operation of the Kafka package modules:

Kafka - constants and messages used by the Kafka package modules

Kafka::IO - object interface to socket communications with the Apache Kafka server

Kafka::Producer - object interface to the producer client

Kafka::Consumer - object interface to the consumer client

Kafka::Message - object interface to the Kafka message properties

Kafka::Protocol - functions to process messages in the Apache Kafka's wire format

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

Kafka::Mock - object interface to the TCP mock server for testing

A wealth of detail about the Apache Kafka and Wire Format:

Main page at http://incubator.apache.org/kafka/

Wire Format at http://cwiki.apache.org/confluence/display/KAFKA/Wire+Format/

Writing a Driver for Kafka at http://cwiki.apache.org/confluence/display/KAFKA/Writing+a+Driver+for+Kafka

AUTHOR ^

Sergey Gladkov, <sgladkov@trackingsoft.com>

CONTRIBUTORS ^

Alexander Solovey

Jeremy Jordan

Vlad Marchenko

COPYRIGHT AND LICENSE ^

Copyright (C) 2012-2013 by TrackingSoft LLC. All rights reserved.

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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