class WaterDrop::Instrumentation::Callbacks::Statistics

Statistics callback handler @note We decorate the statistics with our own decorator because some of the metrics from

rdkafka are absolute. For example number of sent messages increases not in reference to
previous statistics emit but from the beginning of the process. We decorate it with diff
of all the numeric values against the data from the previous callback emit

Public Class Methods

new(producer_id, client_name, monitor) click to toggle source

@param producer_id [String] id of the current producer @param client_name [String] rdkafka client name @param monitor [WaterDrop::Instrumentation::Monitor] monitor we are using

# File lib/waterdrop/instrumentation/callbacks/statistics.rb, line 16
def initialize(producer_id, client_name, monitor)
  @producer_id = producer_id
  @client_name = client_name
  @monitor = monitor
  @statistics_decorator = ::Karafka::Core::Monitoring::StatisticsDecorator.new
end

Public Instance Methods

call(statistics) click to toggle source

Emits decorated statistics to the monitor @param statistics [Hash] rdkafka statistics

# File lib/waterdrop/instrumentation/callbacks/statistics.rb, line 25
def call(statistics)
  # Emit only statistics related to our client
  # rdkafka does not have per-instance statistics hook, thus we need to make sure that we
  # emit only stats that are related to current producer. Otherwise we would emit all of
  # all the time.
  return unless @client_name == statistics['name']

  @monitor.instrument(
    'statistics.emitted',
    producer_id: @producer_id,
    statistics: @statistics_decorator.call(statistics)
  )
# This runs from the rdkafka thread, thus we want to safe-guard it and prevent absolute
# crashes even if the instrumentation code fails. If it would bubble-up, it could crash
# the rdkafka background thread
rescue StandardError => e
  @monitor.instrument(
    'error.occurred',
    caller: self,
    error: e,
    producer_id: @producer_id,
    type: 'callbacks.statistics.error'
  )
end