Module: Karafka::Pro::Processing::Strategies::Dlq::Mom

Includes:
Default
Included in:
Aj::DlqMom, MomVp
Defined in:
lib/karafka/pro/processing/strategies/dlq/mom.rb

Overview

Strategy for supporting DLQ with Mom enabled

Constant Summary collapse

FEATURES =

Features for this strategy

%i[
  dead_letter_queue
  manual_offset_management
].freeze

Instance Method Summary collapse

Methods included from Default

#build_dlq_message, #dispatch_to_dlq, #dispatch_to_dlq?, #find_skippable_message

Methods included from Karafka::Pro::Processing::Strategies::Default

#handle_before_consume, #handle_before_enqueue, #handle_consume, #handle_revoked

Methods included from Karafka::Processing::Strategies::Default

#commit_offsets, #commit_offsets!, #handle_before_consume, #handle_before_enqueue, #handle_consume, #handle_idle, #handle_revoked, #handle_shutdown, #mark_as_consumed, #mark_as_consumed!

Methods included from Karafka::Processing::Strategies::Base

#handle_before_consume, #handle_before_enqueue, #handle_consume, #handle_idle, #handle_revoked, #handle_shutdown

Instance Method Details

#handle_after_consume ⇒ Object

When manual offset management is on, we do not mark anything as consumed automatically and we rely on the user to figure things out



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# File 'lib/karafka/pro/processing/strategies/dlq/mom.rb', line 32

def handle_after_consume
  coordinator.on_finished do
    return if revoked?

    if coordinator.success?
      coordinator.pause_tracker.reset
    elsif coordinator.pause_tracker.attempt <= topic.dead_letter_queue.max_retries
      retry_after_pause
    # If we've reached number of retries that we could, we need to skip the first
    # message that was not marked as consumed, pause and continue, while also moving
    # this message to the dead topic.
    #
    # For a Mom setup, this means, that user has to manage the checkpointing by
    # himself. If no checkpointing is ever done, we end up with an endless loop.
    else
      # We reset the pause to indicate we will now consider it as "ok".
      coordinator.pause_tracker.reset

      skippable_message, = find_skippable_message
      dispatch_to_dlq(skippable_message) if dispatch_to_dlq?

      # Save the next offset we want to go with after moving given message to DLQ
      # Without this, we would not be able to move forward and we would end up
      # in an infinite loop trying to un-pause from the message we've already processed
      # Of course, since it's a MoM a rebalance or kill, will move it back as no
      # offsets are being committed
      coordinator.seek_offset = skippable_message.offset + 1
      pause(coordinator.seek_offset, nil, false)
    end
  end
end