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From Ye Hong <Ye.H...@audiencescience.com>
Subject Partition reassignment causes replica number and Isr to go above configured value
Date Wed, 05 Aug 2015 21:55:28 GMT
Hi All,

We recently performed a partition reassignment on one of our Kafka cluster. (, all
topics configured to have 2 replicas.)

After the completion of reassignment, we have noticed that some of the partitions has 3 replicas
and 3 Isrs instead of 2. 

for example:
    Topic: topic1    Partition: 7    Leader: 5    Replicas: 5,2    Isr: 5,2  (correct number
of replicas and Isr)
    Topic: topic1    Partition: 8    Leader: 6    Replicas: 6,4,2    Isr: 6,4,2  (has more
replica and Isr than configured)
    Topic: topic1    Partition: 32    Leader: 5    Replicas: 5,4,2    Isr: 5,4,2

Previously, we have seen 3 replicas during the reassignment, however, the Isr count was always
2, and replica count will drop back to 2 after the completion of reassignment. 

Just wonder if someone has encountered similar issue. What would be a good way to fix it?
I am thinking about triggering a partial partition reassignment with a manually created partition
assignment config that would bring the replicas back to 2. Is this the right way to fix such



Here are the step we did for the reassignment:
1. /usr/local/kafka/bin/kafka-reassign-partitions.sh --zookeeper <zookeeper_host_name>:<port>
--broker-list "<broker_list>" --generate --topics-to-move-json-file <topics-to-move_json_file>
2. From the console output, copy the second part and put it into a text file assignment_json_file.
3. /usr/local/kafka/bin/kafka-reassign-partitions.sh --zookeeper <zookeeper_host_name>:<port>
--broker-list "<broker_list>" --execute --topics-to-move-json-file <topics-to-move_json_file>
--reassignment-json-file <assignment_json_file>
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