---
id: 4776f3fb-e3e2-4291-ac87-2931501f7b68
---

# Kafka Topic Partitions Out of Sync Incident
---

In this type of incident, the partitions of a Kafka topic become out of sync, which means that some of the messages are not being delivered to the intended consumers. This can happen due to various reasons, such as a network issue, a hardware failure, or a bug in the Kafka software. The consequences of this incident can be serious, as it can cause data loss, message duplication, or other errors in the downstream systems that depend on the Kafka topic. Therefore, it is important to identify and resolve the root cause of the partition sync issue as soon as possible to ensure the reliability and consistency of the data pipeline.

### Parameters
```shell
export ZOOKEEPER_PORT="PLACEHOLDER"

export ZOOKEEPER_HOST="PLACEHOLDER"

export TOPIC_NAME="PLACEHOLDER"

export REPLICATION_FACTOR="PLACEHOLDER"

export PARTITION_COUNT="PLACEHOLDER"

export PATH_TO_KAFKA_HOME="PLACEHOLDER"

export NAME_OF_TOPIC="PLACEHOLDER"
```

## Debug

### List all topics in Kafka
```shell
kafka-topics --list --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT}
```

### Describe a specific topic to check if it has multiple partitions
```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} --topic ${TOPIC_NAME}
```

### Check if any of the Kafka brokers are down
```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} --topic ${TOPIC_NAME} | grep -i "isr:"
```

### Check if there are any under-replicated partitions
```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} | grep -i "under-replicated"
```

## Repair

### Check the topic configuration to ensure that replication and partition counts are correct.
```shell


#!/bin/bash

# Set the variables

KAFKA_HOME=${PATH_TO_KAFKA_HOME}

TOPIC_NAME=${NAME_OF_TOPIC}

REPLICATION_FACTOR=${REPLICATION_FACTOR}

PARTITION_COUNT=${PARTITION_COUNT}



# Check the topic configuration

$KAFKA_HOME/bin/kafka-topics.sh --describe --zookeeper localhost:2181 --topic $TOPIC_NAME | grep -q "Replication Factor: $REPLICATION_FACTOR" 

if [ $? -ne 0 ]; then

    # Update the replication factor

    $KAFKA_HOME/bin/kafka-topics.sh --alter --zookeeper localhost:2181 --topic $TOPIC_NAME --partitions $PARTITION_COUNT --replication-factor $REPLICATION_FACTOR

    echo "Replication factor updated for topic $TOPIC_NAME"

else

    echo "Replication factor is already correct for topic $TOPIC_NAME"

fi


```

In this type of incident, the partitions of a Kafka topic become out of sync, which means that some of the messages are not being delivered to the intended consumers. This can happen due to various reasons, such as a network issue, a hardware failure, or a bug in the Kafka software. The consequences of this incident can be serious, as it can cause data loss, message duplication, or other errors in the downstream systems that depend on the Kafka topic. Therefore, it is important to identify and resolve the root cause of the partition sync issue as soon as possible to ensure the reliability and consistency of the data pipeline.


```shell
export ZOOKEEPER_PORT="PLACEHOLDER"

export ZOOKEEPER_HOST="PLACEHOLDER"

export TOPIC_NAME="PLACEHOLDER"

export REPLICATION_FACTOR="PLACEHOLDER"

export PARTITION_COUNT="PLACEHOLDER"

export PATH_TO_KAFKA_HOME="PLACEHOLDER"

export NAME_OF_TOPIC="PLACEHOLDER"
```


### List all topics in Kafka

```shell
kafka-topics --list --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT}
```

### Describe a specific topic to check if it has multiple partitions

```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} --topic ${TOPIC_NAME}
```

### Check if any of the Kafka brokers are down

```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} --topic ${TOPIC_NAME} | grep -i "isr:"
```

### Check if there are any under-replicated partitions

```shell
kafka-topics --describe --zookeeper ${ZOOKEEPER_HOST}:${ZOOKEEPER_PORT} | grep -i "under-replicated"
```


### Check the topic configuration to ensure that replication and partition counts are correct.

```shell


#!/bin/bash

# Set the variables

KAFKA_HOME=${PATH_TO_KAFKA_HOME}

TOPIC_NAME=${NAME_OF_TOPIC}

REPLICATION_FACTOR=${REPLICATION_FACTOR}

PARTITION_COUNT=${PARTITION_COUNT}



# Check the topic configuration

$KAFKA_HOME/bin/kafka-topics.sh --describe --zookeeper localhost:2181 --topic $TOPIC_NAME | grep -q "Replication Factor: $REPLICATION_FACTOR" 

if [ $? -ne 0 ]; then

    # Update the replication factor

    $KAFKA_HOME/bin/kafka-topics.sh --alter --zookeeper localhost:2181 --topic $TOPIC_NAME --partitions $PARTITION_COUNT --replication-factor $REPLICATION_FACTOR

    echo "Replication factor updated for topic $TOPIC_NAME"

else

    echo "Replication factor is already correct for topic $TOPIC_NAME"

fi


```


Kafka Topic Partitions Out of Sync Incident

Overview

Parameters

Debug

List all topics in Kafka

Describe a specific topic to check if it has multiple partitions

Check if any of the Kafka brokers are down

Check if there are any under-replicated partitions

Repair

Check the topic configuration to ensure that replication and partition counts are correct.

Learn more

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