Since I reused the same consumer group to consume the messages after step 6 data there was no data loss occurred. But if I create a new consumer group for sure the new consumer will suffer data loss.
I am more concerning about if this is an acceptable behavior by Kafka that an out of sync broker can be elected as the leader for a partition. Is there any mechanism built around Kafka to ensure that only the in-sync broker can be chosen to be a leader? If no, what is the best practice to restart brokers if some of the replicas are out of sync? On Tue, Mar 3, 2015 at 2:35 AM, Jiangjie Qin <j...@linkedin.com.invalid> wrote: > In this case you have data loss. In step 6, when broker 1 comes up, it > becomes the leader and has log end offset 1000. When broker 0 comes up, it > becomes follower and will truncate its log to 1000, i.e. 1000 messages > were lost. Next time when the consumer starts, its offset will be reset to > either the smallest or the largest depending on the setting. > > Jiangjie (Becket) Qin > > On 3/2/15, 9:32 AM, "Stuart Reynolds" <s...@stureynolds.com> wrote: > > >Each topic has: earliest and latest offsets (per partition) > >Each consumer group has a current offset (per topic, partition pair) > > > >I see -1 for the current offsets new consumer groups that haven't yet > >committed an offset. I think it means that the offsets for that > >consumer group are undefined. > > > >Is it possible you generated new consumer groups when you restarted your > >broker? > > > > > > > > > >On Mon, Mar 2, 2015 at 3:15 AM, tao xiao <xiaotao...@gmail.com> wrote: > >> Hi team, > >> > >> I have 2 brokers (0 and 1) serving a topic mm-benchmark-test. I did some > >> tests on the two brokers to verify how leader got elected. Here are the > >> steps: > >> > >> 1. started 2 brokers > >> 2. created a topic with partition=1 and replication-factor=2. Now > >>brokers 1 > >> was elected as leader > >> 3. sent 1000 messages to the topic and consumed from a high level > >>consumer > >> using zk as the offset storage. > >> 4. shutdown broker 1 and now broker 0 was elected as leader > >> 5. sent another 1000 messages to topic and consumed again > >> 6. completely shutdown broker 0 and then started broker 1. now broker 1 > >> became the leader > >> 7. started broker 0 and ran ConsumerOffsetChecker which showed negative > >>lag > >> (-1000 in my case) > >> > >> I think this is because the consumed offset in zk was 2000 and logsize > >> retrieved from the leader (broker 1) which missed 1000 messages in step > >>5 > >> in this case was 1000 there -1000 = 1000 - 2000 was given. > >> > >> Is this a bug or expected behavior? > >> > >> -- > >> Regards, > >> Tao > > -- Regards, Tao
