Class: Kafka::Protocol::MetadataResponse

Inherits:
Object
  • Object
show all
Defined in:
lib/kafka/protocol/metadata_response.rb

Overview

A response to a TopicMetadataRequest.

The response contains information on the brokers, topics, and partitions in the cluster.

  • For each broker a node id, host, and port is provided.
  • For each topic partition the node id of the broker acting as partition leader, as well as a list of node ids for the set of replicas, are given. The isr list is the subset of replicas that are "in sync", i.e. have fully caught up with the leader.

API Specification

MetadataResponse => [Broker][TopicMetadata]
  Broker => NodeId Host Port  (any number of brokers may be returned)
    NodeId => int32
    Host => string
    Port => int32

  TopicMetadata => TopicErrorCode TopicName [PartitionMetadata]
    TopicErrorCode => int16

  PartitionMetadata => PartitionErrorCode PartitionId Leader Replicas Isr
    PartitionErrorCode => int16
    PartitionId => int32
    Leader => int32
    Replicas => [int32]
    Isr => [int32]

Defined Under Namespace

Classes: BrokerInfo, PartitionMetadata, TopicMetadata

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(brokers:, topics:) ⇒ MetadataResponse

Returns a new instance of MetadataResponse.


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# File 'lib/kafka/protocol/metadata_response.rb', line 84

def initialize(brokers:, topics:)
  @brokers = brokers
  @topics = topics
end

Instance Attribute Details

#brokersArray<BrokerInfo> (readonly)

Returns the list of brokers in the cluster.

Returns:

  • (Array<BrokerInfo>)

    the list of brokers in the cluster.


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# File 'lib/kafka/protocol/metadata_response.rb', line 79

def brokers
  @brokers
end

#topicsArray<TopicMetadata> (readonly)

Returns the list of topics in the cluster.

Returns:


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# File 'lib/kafka/protocol/metadata_response.rb', line 82

def topics
  @topics
end

Class Method Details

.decode(decoder) ⇒ MetadataResponse

Decodes a MetadataResponse from a Decoder containing response data.

Parameters:

Returns:


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# File 'lib/kafka/protocol/metadata_response.rb', line 147

def self.decode(decoder)
  brokers = decoder.array do
    node_id = decoder.int32
    host = decoder.string
    port = decoder.int32

    BrokerInfo.new(
      node_id: node_id,
      host: host,
      port: port
    )
  end

  topics = decoder.array do
    topic_error_code = decoder.int16
    topic_name = decoder.string

    partitions = decoder.array do
      PartitionMetadata.new(
        partition_error_code: decoder.int16,
        partition_id: decoder.int32,
        leader: decoder.int32,
        replicas: decoder.array { decoder.int32 },
        isr: decoder.array { decoder.int32 },
      )
    end

    TopicMetadata.new(
      topic_error_code: topic_error_code,
      topic_name: topic_name,
      partitions: partitions,
    )
  end

  new(brokers: brokers, topics: topics)
end

Instance Method Details

#find_broker(node_id) ⇒ BrokerInfo

Finds the broker info for the given node id.

Parameters:

  • node_id (Integer)

    the node id of the broker.

Returns:

Raises:


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# File 'lib/kafka/protocol/metadata_response.rb', line 123

def find_broker(node_id)
  broker = @brokers.find {|broker| broker.node_id == node_id }

  raise Kafka::Error, "No broker with id #{node_id}" if broker.nil?

  broker
end

#find_leader_id(topic, partition) ⇒ Integer

Finds the node id of the broker that is acting as leader for the given topic and partition per this metadata.

Parameters:

  • topic (String)

    the name of the topic.

  • partition (Integer)

    the partition number.

Returns:

  • (Integer)

    the node id of the leader.


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# File 'lib/kafka/protocol/metadata_response.rb', line 95

def find_leader_id(topic, partition)
  topic_info = @topics.find {|t| t.topic_name == topic }

  if topic_info.nil?
    raise UnknownTopicOrPartition, "no topic #{topic}"
  end

  Protocol.handle_error(topic_info.topic_error_code)

  partition_info = topic_info.partitions.find {|p| p.partition_id == partition }

  if partition_info.nil?
    raise UnknownTopicOrPartition, "no partition #{partition} in topic #{topic}"
  end

  begin
    Protocol.handle_error(partition_info.partition_error_code)
  rescue ReplicaNotAvailable    # This error can be safely ignored per the protocol specification.

  end

  partition_info.leader
end

#partitions_for(topic_name) ⇒ Object


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# File 'lib/kafka/protocol/metadata_response.rb', line 131

def partitions_for(topic_name)
  topic = @topics.find {|t| t.topic_name == topic_name }

  if topic.nil?
    raise UnknownTopicOrPartition, "unknown topic #{topic_name}"
  end

  Protocol.handle_error(topic.topic_error_code)

  topic.partitions
end