Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
Kafka, mail # user - Partition data for deleted topic found in kafka-logs, also, found leader: -1


Copy link to this message
-
Re: Partition data for deleted topic found in kafka-logs, also, found leader: -1
Yogesh Sangvikar 2013-06-19, 04:42
Hi Team,

Could you please help to understand those features?

Thanks,
Yogesh Sangvikar
On Tue, Jun 18, 2013 at 6:55 PM, Yogesh Sangvikar <
[EMAIL PROTECTED]> wrote:

> Hi Team,
>
> I am exploring kafka 0.8 beta release to understand data flow, replication
> features.
> While testing i found that, the partition data for data for deleted topic
> is preseved in kafka-logs, why this behavior? suppose below case,
>
>  A topic (suppose test1) is created with partition 6 and replication 3 on
> a system with 4 brokers, respective log and index files will be prepared
> per partition in kafka-logs. If I delete the topic and recreate the same
> topic ‘test1’ after some time with partition 2 and replication 2. The
> kafka-logs directory seems to be confusing to understand why the partitions
> for previous topic are present. *Please help to understand this scenario*.
>
> Also, while testing the replication and leader selection feature observed
> leader -1 status,
>
> Original status:
> topic: test1    partition: 0    leader: 4       replicas: 4,2,3 isr: 4,2,3
> topic: test1    partition: 1    leader: 0       replicas: 0,3,4 isr: 0,3,4
> topic: test1    partition: 2    leader: 1       replicas: 1,4,0 isr: 1,4,0
> if leader 4 goes down:
> topic: test1    partition: 0    leader: 2       replicas: 4,2,3 isr: 2,3
> topic: test1    partition: 1    leader: 0       replicas: 0,3,4 isr: 0,3,4
> topic: test1    partition: 2    leader: 1       replicas: 1,4,0 isr: 1,0,4
>
> if leader 2  goes down:
> topic: test1    partition: 0    leader: 3       replicas: 4,2,3 isr: 3
> topic: test1    partition: 1    leader: 0       replicas: 0,3,4 isr: 0,3,4
> topic: test1    partition: 2    leader: 1       replicas: 1,4,0 isr: 1,0,4
>
> if again leader 3 goes down:
> topic: test1    partition: 0    leader: -1      replicas: 4,2,3 isr:
> topic: test1    partition: 1    leader: 0       replicas: 0,3,4 isr: 0,4
> topic: test1    partition: 2    leader: 1       replicas: 1,4,0 isr: 1,0,4
>
> As per kafka protocol guide, *leader: -1 means If no leader exists
> because we are in the middle of a leader election this id will be -1.*
>
> *Does it mean that, the data from partition 0 will be unavailable due no
> leader (leader selection in progress)?*
> As per my understanding, can we have auto re-balancer facility to
> re-balance the partition replications to available brokers if one of the
> broker is down, as in above case of (if leader 4 goes down), we can
> replicate the partition 0 to broker 0/1 to re-balance the replication.
>
> Please correct me for any wrong understanding as those are my initial
> observations.
>
> Thanks in advance.
>
> Thanks,
> Yogesh Sangvikar
>
>
>