Alexandre Dupriez created KAFKA-8695:
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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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