NAME

Kafka::Producer::Avro - Avro message producer for Apache Kafka.

SYNOPSIS

use Kafka::Connection;
use Kafka::Producer::Avro;

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

my $producer = Kafka::Producer::Avro->new( Connection => $connection , SchemaRegistry => Confluent::SchemaRegistry->new() );

# Set Avro schema for message key (valid JSON-string)
my $key_schema = <<KEY_SCHEMA;
      {
              "type": "long",
              "name": "_id"
      }
KEY_SCHEMA
# Set Avro schema for message value (payload) (valid JSON-string)
my $value_schema = <<VALUE_SCHEMA;
      {
              "type": "record",
              "name": "myrecord",
              "fields": [
                      {
                              "name": "f1",
                              "type": "string"
                      }
              ]
      }
VALUE_SCHEMA

# Sending a single message
my $response = $producer->send(
      'mytopic',          # topic
      0,                  # partition
      'Single message',   # message
      undef,              # key
      undef,              # compression_codec
      undef,              # timestamps
      $key_schema,        # key_schema
      $value_schema       # value_schema
);

# Sending a series of messages
$response = $producer->send(
      'mytopic',          # topic
      0,                  # partition
      [                   # messages
              'The first message',
              'The second message',
              'The third message',
      ],
      undef,              # key(s)
      undef,              # compression_codec
      undef,              # timestamp(s)
      $key_schema,        # key_schema
      $value_schema       # value_schema
);

# ...or use named parameters

$producer->send(
      topic             => $topic,
      partition         => $partition,
      messages          => $messages,
      keys              => $keys,
      compression_codec => $compression_codec,
      timestamps        => $timestamps,
      key_schema        => $key_schema,
      value_schema      => $value_schema
);    

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

DESCRIPTION

Kafka::Producer::Avro main feature is to provide object-oriented API to produce messages according to Confluent SchemaRegistry and Avro serialization.

Kafka::Producer::Avro inerhits from and extends Kafka::Producer.

INSTALL

Installation of Kafka::Producer::Avro is a canonical:

perl Makefile.PL
make
make test
make install

TEST NOTES

Tests are focused on verifying Avro-formatted messages and theirs interactions with Confluent Schema Registry and are intended to extend Kafka::Producer test suite.

They expect that in the target are listening Apache Kafka and Schema Registry services, respectively listening on localhost:9092 and http://localhost:8081.

You can alternatively set a different URLs by exporting the following environment variable:

• KAFKA_HOST
• KAFKA_PORT
• CONFLUENT_SCHEMA_REGISTY_URL

For example:

export KAFKA_HOST=my-kafka-host.my-domain.org
export FALFA_PORT=9092
export CONFLUENT_SCHEMA_REGISTY_URL=http://my-schema-registry-host.my-domain.org

USAGE

CONSTRUCTOR

new

Creates new producer client object.

new() takes arguments in key-value pairs as described in Kafka::Producer from which it inherits.

In addition, takes in the following arguments:

• SchemaRegistry => $schema_registry (mandatory)

  Is a Confluent::SchemaRegistry instance.

METHODS

The following methods are defined for the Kafka::Avro::Producer class:

schema_registry()

Returns the Confluent::SchemaRegistry instance supplied to the construcor.

get_error()

Returns a string containing last error message.

send( $topic, $partition, $messages, $keys, $compression_codec, $timestamps, $key_schema, $value_schema )

send( %named_params )

Sends Avro-formatted messages on a Kafka::Connection object.

Returns a non-blank value (a reference to a hash with server response description) if the message is successfully sent.

In order to handle Avro format, Kafka::Producer|Kafka::Producer send() method is extended with two more positional arguments, $key_schema and $value_schema:

$producer->send(
      $topic,             # scalar 
      $partition,         # scalar
      $messages,          # scalar | array
      $keys,              # (optional) undef | scalar | array
      $compression_codec, # (optional) undef | scalar
      $timestamps,        # (optional) undef | scalar | array
      $key_schema,        # (optional) undef | JSON-string
      $value_schema       # (optional) undef | JSON-string
);

Both $key_schema and $value_schema parameters are optional and must provide JSON strings that represent Avro schemas to use to validate and serialize key(s) and value(s).

These schemas are validated against $schema_registry and, if compliant, they are added to the registry under the $topic+'key' or $topic+'value' Schema Registry's subjects.

If an expected schema isn't provided, latest version from Schema Registry is used accordingly to the
(topic + key/value) subject.

Alternatively, for ease of use, the send() method may be also used by suggesting named parameters:

$producer->send(
      topic             => $topic,             # scalar 
      partition         => $partition,         # scalar
      messages          => $messages,          # scalar | array
      keys              => $keys,              # (optional) undef | scalar | array
      compression_codec => $compression_codec, # (optional) undef | scalar
      timestamps        => $timestamps,        # (optional) undef | scalar | array
      key_schema        => $key_schema,        # (optional) undef | JSON-string
      value_schema      => $value_schema       # (optional) undef | JSON-string
);    

bulk_send( %params )

Similar to send but uses bulks to avoid memory leaking.

Extra named parameters are expected:

• size => $size

  The size of the bulk

• on_before_send_bulk => sub {...} (optional)

  A code block that will be executed before the sending of each bulk.

  The block will receive the following positional parameters:

  • $bulk_num the number of the bulk
  • $bulk_messages the number of messages in the bulk
  • $bulk_keys the number of keys in the bulk
  • $index_from the absolute index of the first message in the bulk
  • $index_to the absolute index of the last message in the bulk

• on_after_send_bulk => sub {...} (optional)

  A code block that will be executed after the sending of each bulk.

  The block will receive the following positional parameters:

  • $sent the number of sent messages in the bulk
  • $total_sent the total number of messages sent

• on_init => sub {...} (optional)

  A code block that will be executed only once before at the beginning of the cycle.

  The block will receive the following positional parameters:

  • $to_send the total number of messages to send
  • $bulk_size the size of the bulk

• on_complete => sub {...} (optional)

  A code block that will be executed only once after the end of the cycle.

  The block will receive the following positional parameters:

  • $to_send the total number of messages to send
  • $total_sent the total number of messages sent
  • $errors the number bulks sent with errors

• on_send_error => sub {...} (optional)

  A code block that will be executed when a bulk registers an error.

AUTHOR

Alvaro Livraghi, alvarol@cpan.org

CONTRIBUTE

https://github.com/alivraghi/Kafka-Producer-Avro

BUGS

Please use GitHub project link above to report problems or contact authors.

COPYRIGHT AND LICENSE

Copyright 2018 by Alvaro Livraghi

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.