How to get latest offset for a partition for a kaf

问题:

I am using the Python high level consumer for Kafka and want to know the latest offsets for each partition of a topic. However I cannot get it to work.

from kafka import TopicPartition
from kafka.consumer import KafkaConsumer

con = KafkaConsumer(bootstrap_servers = brokers)
ps = [TopicPartition(topic, p) for p in con.partitions_for_topic(topic)]

con.assign(ps)
for p in ps:
    print "For partition %s highwater is %s"%(p.partition,con.highwater(p))

print "Subscription = %s"%con.subscription()
print "con.seek_to_beginning() = %s"%con.seek_to_beginning()

But the output I get is

For partition 0 highwater is None
For partition 1 highwater is None
For partition 2 highwater is None
For partition 3 highwater is None
For partition 4 highwater is None
For partition 5 highwater is None
....
For partition 96 highwater is None
For partition 97 highwater is None
For partition 98 highwater is None
For partition 99 highwater is None
Subscription = None
con.seek_to_beginning() = None
con.seek_to_end() = None

I have an alternate approach using assign but the result is the same

con = KafkaConsumer(bootstrap_servers = brokers)
ps = [TopicPartition(topic, p) for p in con.partitions_for_topic(topic)]

con.assign(ps)
for p in ps:
    print "For partition %s highwater is %s"%(p.partition,con.highwater(p))

print "Subscription = %s"%con.subscription()
print "con.seek_to_beginning() = %s"%con.seek_to_beginning()
print "con.seek_to_end() = %s"%con.seek_to_end()

It seems from some of the documentation that I might get this behaviour if a fetch has not been issued. But I cannot find a way to force that. What am I doing wrong?

Or is there a different/simpler way to get the latest offsets for a topic?

回答1:

Finally after spending a day on this and several false starts, I was able to find a solution and get it working. Posting it her so that others may refer to it.

from kafka import SimpleClient
from kafka.protocol.offset import OffsetRequest, OffsetResetStrategy
from kafka.common import OffsetRequestPayload

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)

for r in offsets_responses:
    print "partition = %s, offset = %s"%(r.partition, r.offsets[0])

回答2:

If you wish to use Kafka shell scripts present in kafka/bin, then you can get latest and smallest offsets by using kafka-run-class.sh.

To get latest offset command will look like this

bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list localhost:9092 --time -1 --topic topiname

To get smallest offset command will look like this

bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list localhost:9092 --time -2 --topic topiname

You can find more information on Get Offsets Shell from following link

Hope this helps!

回答3:

from kafka import KafkaConsumer, TopicPartition

TOPIC = 'MYTOPIC'
GROUP = 'MYGROUP'
BOOTSTRAP_SERVERS = ['kafka01:9092', 'kafka02:9092']

consumer = KafkaConsumer(
        bootstrap_servers=BOOTSTRAP_SERVERS,
        group_id=GROUP,
        enable_auto_commit=False
    )


for p in consumer.partitions_for_topic(TOPIC):
    tp = TopicPartition(TOPIC, p)
    consumer.assign([tp])
    committed = consumer.committed(tp)
    consumer.seek_to_end(tp)
    last_offset = consumer.position(tp)
    print("topic: %s partition: %s committed: %s last: %s lag: %s" % (TOPIC, p, committed, last_offset, (last_offset - committed)))

consumer.close(autocommit=False)

回答4:

With kafka-python>=1.3.4 you can use:

kafka.KafkaConsumer.end_offsets(partitions)

Get the last offset for the given partitions. The last offset of a partition is the offset of the upcoming message, i.e. the offset of the last available message + 1.

from kafka import TopicPartition
from kafka.consumer import KafkaConsumer

con = KafkaConsumer(bootstrap_servers = brokers)
ps = [TopicPartition(topic, p) for p in con.partitions_for_topic(topic)]

con.end_offsets(ps)

回答5:

Another way to achieve this is by polling the consumer to obtain the last consumed offset and then using the seek_to_end method to obtain the most recent available offset partition.

from kafka import KafkaConsumer
consumer = KafkaConsumer('my-topic',
                     group_id='my-group',
                     bootstrap_servers=['localhost:9092'])
consumer.poll()
consumer.seek_to_end()

This method particularly comes in handy when using consumer groups.

SOURCES:

1. https://kafka-python.readthedocs.io/en/master/apidoc/kafka.consumer.html#kafka.consumer.KafkaConsumer.poll
2. https://kafka-python.readthedocs.io/en/master/apidoc/kafka.consumer.html#kafka.consumer.KafkaConsumer.seek_to_end