Yep, 0 is a non-null value, that is, the consumer group has a committed offset, which in this case happens to be 0. The dash "-" implies an unknown/null value.
In your example with your test topics - the earliest offset in the topic is still 0, and there's not been much data through it, so maybe it makes sense as a default value? But look at the earliest offset on one of our topics, which has a retention time of 7 days (as Kafka offsets are absolute for a topic, never relative): # the -2 arg to time is shorthand for "earliest", -1 is "latest" kafka-run-class kafka.tools.GetOffsetShell --broker-list kafka:9092 --topic trx_reporting --time -2 trx_reporting:0:8681020918 trx_reporting:1:8675438549 trx_reporting:2:8681184674 If I saw a consumer group that listed an offset of 8681020918 on partition 0 of topic trx_reporting, I would think it had previously been consuming that topic. However, an offset of "-" makes it clear that it's never consumed. And it's important that we distinguish "My next offset to read from is 0" from "I have never read from this partition" because of the configuration property available to consumers, auto.offset.reset, which allows you to modify a consumer's behaviour if the last committed offset is null: auto.offset.reset: What to do when there is no initial offset in Kafka or if the current offset does not exist any more on the server (e.g. because that data has been deleted): - earliest: automatically reset the offset to the earliest offset - latest: automatically reset the offset to the latest offset - none: throw exception to the consumer if no previous offset is found for the consumer's group - anything else: throw exception to the consumer. Different applications will have business cases for each possible value. And it requires being able to distinguish a consumer group with a committed offset from a consumer group that's never committed an offset. On Wed, Apr 22, 2020 at 8:02 PM 一直以来 <279377...@qq.com> wrote: > but show "0" and "_", show two value difference??? > thank you ! > > > ------------------ 原始邮件 ------------------ > 发件人: "Liam Clarke-Hutchinson"<liam.cla...@adscale.co.nz>; > 发送时间: 2020年4月21日(星期二) 凌晨4:22 > 收件人: "users"<users@kafka.apache.org>; > > 主题: Re: kafka-consumer-groups.sh CURRENT-OFFSET column show "-" , > what mean about it ! thank you ! > > > > Hi, > > It means the consumer group exists, and Kafka's aware of it's topic > subscriptions, but either the consumers haven't consumed yet (if using auto > offset commit) or the consumers haven't committed any offsets, if using > manual offset committing. > > Does that make sense? > > Kind regards, > > Liam Clarke-Hutchinson > > On Tue, Apr 21, 2020 at 8:12 PM 一直以来 <279377...@qq.com> wrote: > > > ghy@ghy-VirtualBox:~/T/k/bin$ ./kafka-consumer-groups.sh > > --bootstrap-server localhost:9081 --describe --group test > > > > > > GROUP&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > &nbsp;TOPIC&nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp;PARTITION&nbsp; > CURRENT-OFFSET&nbsp; > > LOG-END-OFFSET&nbsp; LAG&nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;CONSUMER-ID&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; HOST&nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; CLIENT-ID > > test&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > myTopic3&nbsp; &nbsp; &nbsp; > > &nbsp; 4&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > -&nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp;1&nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp;-&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;consumer-test-1-d5f2f83d-59fa-4c3b-859d-4219e16479a8 / > 192.168.1.104&nbsp; > > consumer-test-1 > > test&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > myTopic3&nbsp; &nbsp; &nbsp; > > &nbsp; 1&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > -&nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp;1&nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp;-&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;consumer-test-1-d5f2f83d-59fa-4c3b-859d-4219e16479a8 / > 192.168.1.104&nbsp; > > consumer-test-1 > > test&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > myTopic3&nbsp; &nbsp; &nbsp; > > &nbsp; 2&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > -&nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp;0&nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp;-&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;consumer-test-1-d5f2f83d-59fa-4c3b-859d-4219e16479a8 / > 192.168.1.104&nbsp; > > consumer-test-1 > > test&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > myTopic3&nbsp; &nbsp; &nbsp; > > &nbsp; 3&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > -&nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp;1&nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp;-&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;consumer-test-1-d5f2f83d-59fa-4c3b-859d-4219e16479a8 / > 192.168.1.104&nbsp; > > consumer-test-1 > > test&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > myTopic3&nbsp; &nbsp; &nbsp; > > &nbsp; 0&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; > -&nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp; &nbsp; &nbsp;2&nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; &nbsp; > > &nbsp; &nbsp;-&nbsp; &nbsp; &nbsp; &nbsp; > &nbsp; &nbsp; &nbsp; > > &nbsp;consumer-test-1-d5f2f83d-59fa-4c3b-859d-4219e16479a8 / > 192.168.1.104&nbsp; > > consumer-test-1
