Alexey Ozeritskiy created KAFKA-1908:
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Summary: Split brain
Key: KAFKA-1908
URL: https://issues.apache.org/jira/browse/KAFKA-1908
Project: Kafka
Issue Type: Bug
Components: core
Affects Versions: 0.8.2
Reporter: Alexey Ozeritskiy
In some cases, there may be two leaders for one partition.
Steps to reproduce:
# We have 3 brokers, 1 partition with 3 replicas:
{code}
TopicAndPartition: [partition,0] Leader: 1 Replicas: [2,1,3]
ISR: [1,2,3]
{code}
# controller works on broker 3
# let the kafka port be 9092. We execute on broker 1:
{code}
iptables -A INPUT -p tcp --dport 9092 -j REJECT
{code}
# Initiate replica election
# As a result:
Broker 1:
{code}
TopicAndPartition: [partition,0] Leader: 1 Replicas: [2,1,3]
ISR: [1,2,3]
{code}
Broker 2:
{code}
TopicAndPartition: [partition,0] Leader: 2 Replicas: [2,1,3]
ISR: [1,2,3]
{code}
# Flush the iptables rules on broker 1
Now we can produce messages to {code}[partition,0]{code}. Replica-1 will not
receive new data. A consumer can read data from replica-1 or replica-2. When it
reads from replica-1 it resets the offsets and than can read duplicates from
replica-2.
We saw this situation in our production cluster when it had network problems.
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