class `MetadataResponse`

Header File: <libkafka_asio/metadata_response.h>

Namespace: libkafka_asio

Implementation of the Kafka Metadata response, as described on the Kafka wiki. An object of this type will be given as response object to the handler function when invoking a metadata request.

Member Functions

PartitionLeader

Broker::OptionalType PartitionLeader(const String& topic, 
                                     Int32 partition) const

Returns the broker, which is currently acting as leader for the given topic partition. The function basically looks for the given topic and partition in the data of this response object and tries to find the broker with node_id set to the value specified in the leader field of the partition metadata structure. The return value of this function is wrapped using Boost optional. It is empty in case the given topic partition or leading broker cannot be found in the data of this metadata response object.

// Assume the response is an argument of the request handler function
MetadataResponse::OptionalType response;

MetadataResponse::Broker::OptionalType leader = response->PartitionLeader
("foo", 1);
if (leader)
{
    std::cout 
      << "Found leader: " << leader->host << ":" << leader->port
      << std::endl;
}

brokers

const BrokerVector& brokers() const

Returns a reference to the set of received broker metadata. See the Broker data structure below.

topics

const TopicVector& topics() const

Returns a reference to the received topic partition metadata. See the description for Topic and Topic::Partition types below.

Types

Broker

struct Broker

node_id: ID of the Kafka broker
host: Kafka broker hostname
port: Kafka broker port

Topic

struct Topic

error_code: Kafka error code for this topic.
topic_name: Name of this topic.
partitions: Metadata for each requested partition of this topic. This can be empty in case of an error for this topic (e.g. in case the topic cannot be found on the connected broker).

Topic::Partition

struct Topic::Partition

error_code: Kafka error code for this partition.
partition: Number, identifying this topic partition.
leader: Node ID of the Kafka broker, which is currently acting as leader for this partition.
replicas: Set of Kafka broker node IDs that are currently acting as slaves for the leader for this partition.
isr: Set of Kafka broker node IDs that are "caught up" to the leader broker.

OptionalType

typedef boost::optional<MetadataResponse> OptionalType

A metadata response object wrapped using Boost optional. Such an object will be used for metadata request handler functions.

BrokerVector

typedef std::vector<Broker> BrokerVector

Set of brokers.

TopicVector

typedef std::vector<Topic> TopicVector

Set of topic metadata structures.

Broker::OptionalType

typedef boost::optional<Broker> Broker::OptionalType

Broker data structure wrapped using Boost optional.

class MetadataResponse