from kafka import SimpleClient, KafkaConsumer
from kafka.common import OffsetRequestPayload, TopicPartition

def get_topic_offset(brokers, topic):
  """
  獲取一個topic的offset值的和
  """
  client = SimpleClient(brokers)
  partitions = client.topic_partitions[topic]
  offset_requests = [OffsetRequestPayload(topic, p, -1, 1) for p in partitions.keys()]
  offsets_responses = client.send_offset_request(offset_requests)
  return sum([r.offsets[0] for r in offsets_responses])


def get_group_offset(brokers, group_id, topic):
  """
  獲取一個topic特定group已經消費的offset值的和
  """
  consumer = KafkaConsumer(bootstrap_servers=brokers,
               group_id=group_id,
               )
  pts = [TopicPartition(topic=topic, partition=i) for i in
      consumer.partitions_for_topic(topic)]
  result = consumer._coordinator.fetch_committed_offsets(pts)
  return sum([r.offset for r in result.values()])


if __name__ == '__main__':
  topic_offset = get_topic_offset("brokers", "topic")
  group_offset = get_group_offset("brokers", "group_id", "topic")
  lag = topic_offset - group_offset