Class: Karafka::Web::Management::Actions::CreateTopics

Inherits:
Base
  • Object
show all
Defined in:
lib/karafka/web/management/actions/create_topics.rb

Overview

Creates all the needed topics (if they don’t exist). It does not populate data.

Instance Method Summary collapse

Instance Method Details

#call(replication_factor) ⇒ Object

Note:

The order of creation of those topics is important. In order to support the zero-downtime bootstrap, we use the presence of the states topic and its initial state existence as an indicator that the setup went as expected. It the consumers states topic exists and contains needed data, it means all went as expected and that topics created before it also exist (as no error).

Runs the creation process

Parameters:

  • replication_factor (Integer) —

    replication factor for Web-UI topics



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# File 'lib/karafka/web/management/actions/create_topics.rb', line 19

def call(replication_factor)
  consumers_states_topic = ::Karafka::Web.config.topics.consumers.states
  consumers_metrics_topic = ::Karafka::Web.config.topics.consumers.metrics
  consumers_reports_topic = ::Karafka::Web.config.topics.consumers.reports
  errors_topic = ::Karafka::Web.config.topics.errors

  if existing_topics_names.include?(errors_topic)
    exists(errors_topic)
  else
    creating(errors_topic)
    # All the errors will be dispatched here
    # This topic can have multiple partitions but we go with one by default. A single
    # Ruby process should not crash that often and if there is an expectation of a higher
    # volume of errors, this can be changed by the end user
    ::Karafka::Admin.create_topic(
      errors_topic,
      1,
      replication_factor,
      # Remove really old errors (older than 3 months just to preserve space)
      {
        'cleanup.policy': 'delete',
        'retention.ms': 3 * 31 * 24 * 60 * 60 * 1_000 # 3 months
      }
    )
    created(errors_topic)
  end

  if existing_topics_names.include?(consumers_reports_topic)
    exists(consumers_reports_topic)
  else
    creating(consumers_reports_topic)
    # This topic needs to have one partition
    ::Karafka::Admin.create_topic(
      consumers_reports_topic,
      1,
      replication_factor,
      # We do not need to to store this data for longer than 1 day as this data is only
      # used to materialize the end states
      # On the other hand we do not want to have it really short-living because in case
      # of a consumer crash, we may want to use this info to catch up and backfill the
      # state.
      #
      # In case its not consumed because no processes are running, it also usually means
      # there's no data to consume because no karafka servers report
      {
        'cleanup.policy': 'delete',
        'retention.ms': 24 * 60 * 60 * 1_000 # 1 day
      }
    )
    created(consumers_reports_topic)
  end

  if existing_topics_names.include?(consumers_metrics_topic)
    exists(consumers_metrics_topic)
  else
    creating(consumers_metrics_topic)
    # This topic needs to have one partition
    # Same as states - only most recent is relevant as it is a materialized state
    ::Karafka::Admin.create_topic(
      consumers_metrics_topic,
      1,
      replication_factor,
      {
        'cleanup.policy': 'compact',
        'retention.ms': 60 * 60 * 1_000, # 1h
        'segment.ms': 24 * 60 * 60 * 1_000, # 1 day
        'segment.bytes': 104_857_600 # 100MB
      }
    )
    created(consumers_metrics_topic)
  end

  # Create only if needed
  if existing_topics_names.include?(consumers_states_topic)
    exists(consumers_states_topic)
  else
    creating(consumers_states_topic)
    # This topic needs to have one partition
    ::Karafka::Admin.create_topic(
      consumers_states_topic,
      1,
      replication_factor,
      # We care only about the most recent state, previous are irrelevant. So we can
      # easily compact after one minute. We do not use this beyond the most recent
      # collective state, hence it all can easily go away. We also limit the segment
      # size to at most 100MB not to use more space ever.
      {
        'cleanup.policy': 'compact',
        'retention.ms': 60 * 60 * 1_000,
        'segment.ms': 24 * 60 * 60 * 1_000, # 1 day
        'segment.bytes': 104_857_600 # 100MB
      }
    )
    created(consumers_states_topic)
  end
end