Under Replicated Partitions

Introduction

What is Under Replicated Partitions? Under replicated partitions mean followers are not caught up.

Understanding the topic

What happens — Under Replicated Partitions:

• Identify topic, partition, offset scope.
• Check broker health and ISR.
• Inspect consumer errors and deploys.
• Remediate: scale, DLT, replay, or fix schema.

Visual explanation

Pipeline view:

Incident
  ↓
topic/partition/offset
  ↓
producer metrics
  ↓
broker health
  ↓
consumer processing
  ↓
commit/replay decision

Step-by-step explanation

1. Alert — Lag, URP, error rate.
2. Diagnose — Partition-level view.
3. Fix — DLT, scale, rollback.
4. Postmortem — Document root cause.

Informative example

Example:

kafka-topics --bootstrap-server localhost:9092 --create --topic under-replicated-partitions --partitions 6 --replication-factor 3
kafka-console-producer --bootstrap-server localhost:9092 --topic under-replicated-partitions
kafka-console-consumer --bootstrap-server localhost:9092 --topic under-replicated-partitions --from-beginning
kafka-consumer-groups --bootstrap-server localhost:9092 --describe --group under-replicated-partitions-service

Execution workflow

Best practices

• Preserve sample records and offsets before remediation.
• Separate retryable, poison, and infrastructure failures.
• Use DLT and replay tools with audit logs.
• Run recovery drills before real incidents.

Common mistakes

• Resetting offsets without approval or evidence.
• Scaling consumers when the real issue is partition skew.
• Deleting poison messages without root-cause analysis.

Summary

Under Replicated Partitions — Work from evidence by topic-partition-offset, not from guesses or dashboards alone.