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From "Alexandre Dupriez (JIRA)" <j...@apache.org>
Subject [jira] [Created] (KAFKA-8695) Metrics UnderReplicated and UnderMinSir are diverging when configuration is inconsistent
Date Mon, 22 Jul 2019 15:09:00 GMT
Alexandre Dupriez created KAFKA-8695:
----------------------------------------

             Summary: Metrics UnderReplicated and UnderMinSir are diverging when configuration
is inconsistent
                 Key: KAFKA-8695
                 URL: https://issues.apache.org/jira/browse/KAFKA-8695
             Project: Kafka
          Issue Type: Bug
          Components: core
    Affects Versions: 2.3.0, 2.1.1, 2.2.0, 2.1.0
            Reporter: Alexandre Dupriez


As of now, Kafka allows the replication factor of a topic and "min.insync.replicas" to be
set such that "min.insync.replicas" > the topic's replication factor.

As a consequences, the JMX beans
{code:java}
kafka.cluster:type=Partition,name=UnderReplicated{code}
and 
{code:java}
kafka.cluster:type=Partition,name=UnderMinIsr{code}
can report diverging views on the replication for a topic. The former can report no under
replicated partition, while the second will report under in-sync replicas.

 

Even worse, consumption of topics which exhibit this behaviour seems to fail, the Kafka broker
throwing a NotEnoughReplicasException.

 

 
{code:java}
[2019-07-22 10:44:29,913] ERROR [ReplicaManager broker=0] Error processing append operation
on partition __consumer_offsets-0 (kafka.server.ReplicaManager)
org.apache.kafka.common.errors.NotEnoughReplicasException: The size of the current ISR Set(0)
is insufficient to satisfy the min.isr requirement of 2 for partition __consumer_offsets-0{code}
 

 

In order to avoid this scenario, one possibility would be to check the values of "min.insync.replicas"
and "default.replication.factor" when the broker starts, and "min.insync.replicas" and the
replication factor given to a topic at creation time, and refuses to create the topic if those
are inconsistently set.

 



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