Class: Kafka::FFI::TopicConfig

Inherits:
OpaquePointer show all
Defined in:
lib/kafka/ffi/topic_config.rb

Overview

TopicConfig can be passed to Topic.new to configure how the client interacts with the Topic.

Instance Attribute Summary

Attributes inherited from OpaquePointer

#pointer

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from OpaquePointer

by_ref, from_native, inherited, #initialize, to_native

Constructor Details

This class inherits a constructor from Kafka::FFI::OpaquePointer

Class Method Details

.new ⇒ Object 



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# File 'lib/kafka/ffi/topic_config.rb', line 10

def self.new
  Kafka::FFI.rd_kafka_topic_conf_new
end

Instance Method Details

#destroy ⇒ Object

Note:

Never call #destroy on a Config that has been passed to Kafka::FFI.rd_kafka_topic_new since the handle will take ownership of the config.

Free all resources used by the topic config.



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# File 'lib/kafka/ffi/topic_config.rb', line 120

def destroy
  if !pointer.null?
    ::Kafka::FFI.rd_kafka_topic_conf_destroy(self)
  end
end

#dup ⇒ TopicConfig

Duplicate the current config

Returns:



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# File 'lib/kafka/ffi/topic_config.rb', line 80

def dup
  ::Kafka::FFI.rd_kafka_topic_conf_dup(self)
end

#get(key) ⇒ String, :unknown

Get the current config value for the given key.

Parameters:

  • key (String) —

    Config key to fetch the setting for.

Returns:

  • (String, :unknown) —

    Value for the key or :unknown if not already set.



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# File 'lib/kafka/ffi/topic_config.rb', line 50

def get(key)
  key = key.to_s

  # Will contain the size of the value at key
  size = ::FFI::MemoryPointer.new(:size_t)

  # Make an initial request for the size of buffer we need to allocate.
  # When trying to make a guess at the potential size the code would often
  # segfault due to rd_kafka_conf_get reallocating the buffer.
  err = ::Kafka::FFI.rd_kafka_topic_conf_get(self, key, ::FFI::Pointer::NULL, size)
  if err != :ok
    return err
  end

  # Allocate a string long enough to contain the whole value.
  value = ::FFI::MemoryPointer.new(:char, size.read(:size_t))
  err = ::Kafka::FFI.rd_kafka_topic_conf_get(self, key, value, size)
  if err != :ok
    return err
  end

  value.read_string
ensure
  size.free if size
  value.free if value
end

#set(key, value) ⇒ Object

Set the config option at ‘key` to `value`. The configuration options match those used by librdkafka (and the Java client).

Parameters:

  • key (String) —

    Configuration key

  • value (String) —

    Value to set

Raises:

See Also:



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# File 'lib/kafka/ffi/topic_config.rb', line 24

def set(key, value)
  key = key.to_s
  value = value.to_s

  error = ::FFI::MemoryPointer.new(:char, 512)
  result = ::Kafka::FFI.rd_kafka_topic_conf_set(self, key, value, error, error.size)

  # See config_result enum in ffi.rb
  case result
  when :ok
    nil
  when :unknown
    raise Kafka::FFI::UnknownConfigKey.new(key, value, error.read_string)
  when :invalid
    raise Kafka::FFI::InvalidConfigValue.new(key, value, error.read_string)
  end
ensure
  error.free if error
end

#set_partitioner_cb {|topic, key, partition_count| ... } ⇒ Object

Sets a custom partitioner callback that is called for each message to determine which partition to publish the message to.

Examples:

Random partitioner

set_partitioner_cb do |_topic, _key, parts|
  rand(parts)
end

Yields:

  • (topic, key, partition_count)

Yield Parameters:

  • topic (Topic) —

    Topic the message is being published to

  • key (String) —

    Partitioning key provided when publishing

  • partition_count (Integer) —

    Number of partitions the topic has

Yield Returns:

  • (Integer) —

    The partition to publish the message to

See Also:

  • config option for predefined strategies


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# File 'lib/kafka/ffi/topic_config.rb', line 99

def set_partitioner_cb
  if !block_given?
    raise ArgumentError, "set_partitioner_cb must be called with a block"
  end

  # @todo How do we guarantee the block does not get garbage collected?
  # @todo Support opaque pointers?
  cb = ::FFI::Function.new(:int, [:pointer, :string, :size_t, :int32, :pointer, :pointer]) do |topic, key, _, partitions, _, _|
    topic = Topic.new(topic)

    yield(topic, key, partitions)
  end

  ::Kafka::FFI.rd_kafka_topic_conf_set_partitioner_cb(self, cb)
end