Module: Karafka::Processing::Strategies::Default

Includes:
Base
Included in:
Karafka::Pro::Processing::Strategies::Default, Dlq, Mom
Defined in:
lib/karafka/processing/strategies/default.rb

Overview

No features enabled. No manual offset management No long running jobs Nothing. Just standard, automatic flow

Constant Summary collapse

FEATURES =

Apply strategy for a non-feature based flow

%i[].freeze

Instance Method Summary collapse

Instance Method Details

#commit_offsets(async: true) ⇒ Boolean

Note:

Due to its async nature, this may not fully represent the offset state in some edge cases (like for example going beyond max.poll.interval)

Triggers an async offset commit

Parameters:

  • async (Boolean) (defaults to: true) —

    should we use async (default) or sync commit

Returns:

  • (Boolean) —

    true if we still own the partition.



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# File 'lib/karafka/processing/strategies/default.rb', line 94

def commit_offsets(async: true)
  # Do not commit if we already lost the assignment
  return false if revoked?
  return true if client.commit_offsets(async: async)

  # This will once more check the librdkafka revocation status and will revoke the
  # coordinator in case it was not revoked
  revoked?
end

#commit_offsets! ⇒ Boolean

Note:

This is fully synchronous, hence the result of this can be used in DB transactions etc as a way of making sure, that we still own the partition.

Triggers a synchronous offsets commit to Kafka

Returns:

  • (Boolean) —

    true if we still own the partition, false otherwise.



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# File 'lib/karafka/processing/strategies/default.rb', line 109

def commit_offsets!
  commit_offsets(async: false)
end

#handle_after_consume ⇒ Object

Standard flow marks work as consumed and moves on if everything went ok. If there was a processing error, we will pause and continue from the next message (next that is +1 from the last one that was successfully marked as consumed)



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# File 'lib/karafka/processing/strategies/default.rb', line 140

def handle_after_consume
  return if revoked?

  if coordinator.success?
    coordinator.pause_tracker.reset

    # We should not move the offset automatically when the partition was paused
    # If we would not do this upon a revocation during the pause time, a different process
    # would pick not from the place where we paused but from the offset that would be
    # automatically committed here
    return if coordinator.manual_pause?

    mark_as_consumed(messages.last)
  else
    retry_after_pause
  end
end

#handle_before_consume ⇒ Object

Increment number of attempts



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# File 'lib/karafka/processing/strategies/default.rb', line 114

def handle_before_consume
  coordinator.pause_tracker.increment
end

#handle_consume ⇒ Object

Run the user consumption code



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# File 'lib/karafka/processing/strategies/default.rb', line 119

def handle_consume
  Karafka.monitor.instrument('consumer.consume', caller: self)
  Karafka.monitor.instrument('consumer.consumed', caller: self) do
    consume
  end

  # Mark job as successful
  coordinator.success!(self)
rescue StandardError => e
  coordinator.failure!(self, e)

  # Re-raise so reported in the consumer
  raise e
ensure
  # We need to decrease number of jobs that this coordinator coordinates as it has finished
  coordinator.decrement(:consume)
end

#handle_eofed ⇒ Object

Runs the consumer ‘#eofed` method with reporting



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# File 'lib/karafka/processing/strategies/default.rb', line 166

def handle_eofed
  Karafka.monitor.instrument('consumer.eof', caller: self)
  Karafka.monitor.instrument('consumer.eofed', caller: self) do
    eofed
  end
ensure
  coordinator.decrement(:eofed)
end

#handle_idle ⇒ Object

Code that should run on idle runs without messages available



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# File 'lib/karafka/processing/strategies/default.rb', line 159

def handle_idle
  nil
ensure
  coordinator.decrement(:idle)
end

#handle_initialized ⇒ Object

Note:

It runs in the listener loop. Should not be used for anything heavy or with any potential errors. Mostly for initialization of states, etc.

Runs the post-creation, post-assignment code



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# File 'lib/karafka/processing/strategies/default.rb', line 37

def handle_initialized
  Karafka.monitor.instrument('consumer.initialize', caller: self)
  Karafka.monitor.instrument('consumer.initialized', caller: self) do
    initialized
  end
end

#handle_revoked ⇒ Object

We need to always un-pause the processing in case we have lost a given partition. Otherwise the underlying librdkafka would not know we may want to continue processing and the pause could in theory last forever



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# File 'lib/karafka/processing/strategies/default.rb', line 178

def handle_revoked
  resume

  coordinator.revoke

  Karafka.monitor.instrument('consumer.revoke', caller: self)
  Karafka.monitor.instrument('consumer.revoked', caller: self) do
    revoked
  end
ensure
  coordinator.decrement(:revoked)
end

#handle_shutdown ⇒ Object

Runs the shutdown code



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# File 'lib/karafka/processing/strategies/default.rb', line 192

def handle_shutdown
  Karafka.monitor.instrument('consumer.shutting_down', caller: self)
  Karafka.monitor.instrument('consumer.shutdown', caller: self) do
    shutdown
  end
ensure
  coordinator.decrement(:shutdown)
end

#mark_as_consumed(message) ⇒ Boolean

Note:

We keep track of this offset in case we would mark as consumed and got error when processing another message. In case like this we do not pause on the message we’ve already processed but rather at the next one. This applies to both sync and async versions of this method.

Marks message as consumed in an async way.

Parameters:

Returns:

  • (Boolean) —

    true if we were able to mark the offset, false otherwise. False indicates that we were not able and that we have lost the partition.



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# File 'lib/karafka/processing/strategies/default.rb', line 54

def mark_as_consumed(message)
  # seek offset can be nil only in case `#seek` was invoked with offset reset request
  # In case like this we ignore marking
  return true if coordinator.seek_offset.nil?
  # Ignore earlier offsets than the one we already committed
  return true if coordinator.seek_offset > message.offset
  return false if revoked?
  return revoked? unless client.mark_as_consumed(message)

  coordinator.seek_offset = message.offset + 1

  true
end

#mark_as_consumed!(message) ⇒ Boolean

Marks message as consumed in a sync way.

Parameters:

Returns:

  • (Boolean) —

    true if we were able to mark the offset, false otherwise. False indicates that we were not able and that we have lost the partition.



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# File 'lib/karafka/processing/strategies/default.rb', line 73

def mark_as_consumed!(message)
  # seek offset can be nil only in case `#seek` was invoked with offset reset request
  # In case like this we ignore marking
  return true if coordinator.seek_offset.nil?
  # Ignore earlier offsets than the one we already committed
  return true if coordinator.seek_offset > message.offset
  return false if revoked?

  return revoked? unless client.mark_as_consumed!(message)

  coordinator.seek_offset = message.offset + 1

  true
end