---
id: f87df775-df58-43fa-88f1-5c0cfd388031
---

# Redis Replication Lag Issues
---

Redis is an open-source, in-memory data structure store. It is widely used as a database, cache, and message broker. Redis replication lag issues occur when there is a delay in the synchronization of data between master and slave Redis instances. This can happen due to a variety of reasons, such as network latency, high load on the master, or hardware failures. When replication lag occurs, the slave Redis instances are unable to catch up with the master, resulting in data inconsistencies and potentially leading to application failures. It is important to identify and resolve replication lag issues quickly to ensure the reliability and performance of Redis-based applications.

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

export REDIS_HOST="PLACEHOLDER"

export NEW_BUFFER_SIZE="PLACEHOLDER"

export REDIS_CONF_FILE_PATH="PLACEHOLDER"
```

## Debug

### Check if Redis is running
```shell
systemctl status redis
```

### Check Redis replication status
```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info replication
```

### Check Redis key space
```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info keyspace
```

### Check Redis memory usage
```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info memory
```

### Check Redis slow log
```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} slowlog get
```

### Check system memory usage
```shell
free -m
```

### Check system CPU usage
```shell
top
```

### Check network connectivity
```shell
ping ${REDIS_HOST}
```

### Check Redis configuration file
```shell
cat /etc/redis/redis.conf
```

## Repair

### Increase the replication buffer size to reduce the number of missed commands.
```shell


#!/bin/bash



# Set the Redis configuration file path

REDIS_CONF=${REDIS_CONF_FILE_PATH}



# Set the replication buffer size

REPL_BUFFER_SIZE=${NEW_BUFFER_SIZE}



# Update the Redis configuration file with the new replication buffer size

sed -i "s/^repl-backlog-size .*/repl-backlog-size $REPL_BUFFER_SIZE/" $REDIS_CONF



# Restart the Redis service to apply the changes

service redis restart


```

Redis is an open-source, in-memory data structure store. It is widely used as a database, cache, and message broker. Redis replication lag issues occur when there is a delay in the synchronization of data between master and slave Redis instances. This can happen due to a variety of reasons, such as network latency, high load on the master, or hardware failures. When replication lag occurs, the slave Redis instances are unable to catch up with the master, resulting in data inconsistencies and potentially leading to application failures. It is important to identify and resolve replication lag issues quickly to ensure the reliability and performance of Redis-based applications.


```shell
export REDIS_PORT="PLACEHOLDER"

export REDIS_HOST="PLACEHOLDER"

export NEW_BUFFER_SIZE="PLACEHOLDER"

export REDIS_CONF_FILE_PATH="PLACEHOLDER"
```


### Check if Redis is running

```shell
systemctl status redis
```

### Check Redis replication status

```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info replication
```

### Check Redis key space

```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info keyspace
```

### Check Redis memory usage

```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} info memory
```

### Check Redis slow log

```shell
redis-cli -h ${REDIS_HOST} -p ${REDIS_PORT} slowlog get
```

### Check system memory usage

```shell
free -m
```

### Check system CPU usage

```shell
top
```

### Check network connectivity

```shell
ping ${REDIS_HOST}
```

### Check Redis configuration file

```shell
cat /etc/redis/redis.conf
```


### Increase the replication buffer size to reduce the number of missed commands.

```shell


#!/bin/bash



# Set the Redis configuration file path

REDIS_CONF=${REDIS_CONF_FILE_PATH}



# Set the replication buffer size

REPL_BUFFER_SIZE=${NEW_BUFFER_SIZE}



# Update the Redis configuration file with the new replication buffer size

sed -i "s/^repl-backlog-size .*/repl-backlog-size $REPL_BUFFER_SIZE/" $REDIS_CONF



# Restart the Redis service to apply the changes

service redis restart


```


Redis Replication Lag Issues

Overview

Parameters

Debug

Check if Redis is running

Check Redis replication status

Check Redis key space

Check Redis memory usage

Check Redis slow log

Check system memory usage

Check system CPU usage

Check network connectivity

Check Redis configuration file

Repair

Increase the replication buffer size to reduce the number of missed commands.

Learn more

Related Runbooks

Support