Class: Kafka::FetchOperation

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

Overview

Fetches messages from one or more partitions.

operation = Kafka::FetchOperation.new( cluster: cluster, logger: logger, min_bytes: 1, max_wait_time: 10, ) # These calls will schedule fetches from the specified topics/partitions. operation.fetch_from_partition("greetings", 42, offset: :latest, max_bytes: 100000) operation.fetch_from_partition("goodbyes", 13, offset: :latest, max_bytes: 100000) operation.execute

Instance Method Summary collapse

Constructor Details

#initialize(cluster:, logger:, min_bytes: 1, max_bytes: 10485760, max_wait_time: 5) ⇒ FetchOperation

Returns a new instance of FetchOperation.

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# File 'lib/kafka/fetch_operation.rb', line 24 def initialize(cluster:, logger:, min_bytes: 1, max_bytes: 10485760, max_wait_time: 5) @cluster = cluster @logger = TaggedLogger.new(logger) @min_bytes = min_bytes @max_bytes = max_bytes @max_wait_time = max_wait_time @topics = {} @offset_resolver = Kafka::FetchedOffsetResolver.new( logger: logger ) end

Instance Method Details

#execute ⇒ Object 

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# File 'lib/kafka/fetch_operation.rb', line 51 def execute @cluster.add_target_topics(@topics.keys) @cluster.refresh_metadata_if_necessary! topics_by_broker = {} if @topics.none? {|topic, partitions| partitions.any? } raise NoPartitionsToFetchFrom end @topics.each do |topic, partitions| partitions.each do |partition, options| broker = @cluster.get_leader(topic, partition) topics_by_broker[broker] ||= {} topics_by_broker[broker][topic] ||= {} topics_by_broker[broker][topic][partition] = options end end topics_by_broker.flat_map do |broker, topics| @offset_resolver.resolve!(broker, topics) options = { max_wait_time: @max_wait_time * 1000, # Kafka expects ms, not secs  min_bytes: @min_bytes, max_bytes: @max_bytes, topics: topics, } response = broker.fetch_messages(**options) response.topics.flat_map do |fetched_topic| fetched_topic.partitions.map do |fetched_partition| begin Protocol.handle_error(fetched_partition.error_code) rescue Kafka::OffsetOutOfRange => e e.topic = fetched_topic.name e.partition = fetched_partition.partition e.offset = topics.fetch(e.topic).fetch(e.partition).fetch(:fetch_offset) raise e rescue Kafka::Error => e topic = fetched_topic.name partition = fetched_partition.partition @logger.error "Failed to fetch from #{topic}/#{partition}: #{e.message}" raise e end Kafka::FetchedBatchGenerator.new( fetched_topic.name, fetched_partition, topics.fetch(fetched_topic.name).fetch(fetched_partition.partition).fetch(:fetch_offset), logger: @logger ).generate end end end rescue Kafka::ConnectionError, Kafka::LeaderNotAvailable, Kafka::NotLeaderForPartition @cluster.mark_as_stale! raise end

#fetch_from_partition(topic, partition, offset: :latest, max_bytes: 1048576) ⇒ Object 

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# File 'lib/kafka/fetch_operation.rb', line 37 def fetch_from_partition(topic, partition, offset: :latest, max_bytes: 1048576) if offset == :earliest offset = -2 elsif offset == :latest offset = -1 end @topics[topic] ||= {} @topics[topic][partition] = { fetch_offset: offset, max_bytes: max_bytes, } end