---
id: 9a8e91e7-2e09-4ebb-9a83-8b480782a8b7
---

# MySQL Slave Replication Lag
---

MySQL Slave Replication Lag is an incident that occurs when there is a delay or lag in the replication of data from the master MySQL server to the slave MySQL server. This can happen due to various reasons such as network latency, high load on the master server, or configuration issues. This can lead to data inconsistency and affect the overall performance of the application or service that relies on the MySQL database.

### Parameters
```shell
# Environment Variables

export USERNAME="PLACEHOLDER"

export MASTER_SERVER="PLACEHOLDER"

export SLAVE_SERVER="PLACEHOLDER"

export SLAVE_MYSQL_SERVER_IP="PLACEHOLDER"

export MASTER_MYSQL_SERVER_IP="PLACEHOLDER"

```

## Debug

### Check MySQL service status
```shell
systemctl status mysql
```

### Verify if replication is running and check its status
```shell
mysql -u ${USERNAME} -p -e "SHOW SLAVE STATUS\G"
```

### Check the log files of both the master and slave servers
```shell
tail -f /var/log/mysql/error.log
```

### Check the network connectivity and latency between the master and slave servers
```shell
ping ${MASTER_SERVER}

ping ${SLAVE_SERVER}

traceroute ${MASTER_SERVER}

traceroute ${SLAVE_SERVER}
```

### Check the load on the master server
```shell
top
```

### Check the MySQL configuration files on both servers
```shell
cat /etc/mysql/my.cnf
```

### Check the disk usage and available space on both servers
```shell
df -h
```

### Check the MySQL version and compare it on both servers
```shell
mysql -u ${USERNAME} -p -e "SELECT VERSION();"
```
### Measure the replication lag of a MySQL database
```shell
mysql -u ${USERNAME} -p -e "SHOW SLAVE STATUS\G" | grep Seconds_Behind_Master | awk '{print $2}'

```
## Repair

### Define variables
```shell
MASTER_SERVER=${MASTER_MYSQL_SERVER_IP}

SLAVE_SERVER=${SLAVE_MYSQL_SERVER_IP}
```

### Check network connectivity
```shell
ping -c 3 $MASTER_SERVER > /dev/null 2>&1

if [ $? -eq 0 ]; then

    echo "Network connectivity between master and slave MySQL servers is OK."

else

    echo "Network connectivity between master and slave MySQL servers is not OK."

fi
```

### Check the configuration of the MySQL replication process and ensure that it is correctly set up.
```shell
bash

#!/bin/bash

# Stop the MySQL service

sudo systemctl stop mysql.service

# Backup the my.cnf file

sudo cp /etc/mysql/my.cnf /etc/mysql/my.cnf.bak

# Edit the my.cnf file

sudo sed -i 's/^server-id/#server-id/' /etc/mysql/my.cnf

sudo sed -i 's/^log_bin/#log_bin/' /etc/mysql/my.cnf

sudo sed -i 's/^binlog_do_db/#binlog_do_db/' /etc/mysql/my.cnf

sudo sed -i 's/^replicate_do_db/#replicate_do_db/' /etc/mysql/my.cnf

# Start the MySQL service

sudo systemctl start mysql.service

echo "MySQL replication configuration has been checked and updated."

```

MySQL Slave Replication Lag is an incident that occurs when there is a delay or lag in the replication of data from the master MySQL server to the slave MySQL server. This can happen due to various reasons such as network latency, high load on the master server, or configuration issues. This can lead to data inconsistency and affect the overall performance of the application or service that relies on the MySQL database.


This incident type refers to a situation where a SQL Server database is not marked for replication sync, which means it may not be synced with its backup. This can result in data loss or inconsistencies between the primary database and its backup. It is important to address this issue promptly to ensure data integrity and prevent potential downtime or data loss.


SQL Server database not marked for replication sync.

The Redis too many masters incident occurs when there are too many master nodes in a Redis cluster, leading to connection issues and potential data loss. This can happen due to misconfiguration, network issues, or other factors, and requires immediate attention to prevent further damage.


Redis too many masters incident

This incident type refers to an issue with Redis replication, which means that there is a problem with the synchronization of data between Redis instances. This issue could impact the availability and performance of the system and may require immediate attention to restore the replication and ensure data consistency. The incident could be caused by various factors, such as network problems, hardware failures, or configuration issues. The incident must be investigated and resolved as soon as possible to avoid any data loss or downtime.


Redis replication broken incident.

This incident type refers to an issue with Redis where one or more slave instances have become disconnected, resulting in replication failure. This can cause data inconsistencies and may require immediate attention to restore normal functioning. The incident may be caused by a variety of factors, such as network issues, server failures, or misconfiguration.


Redis disconnected slaves incident

This incident type refers to a high replication delay in a PostgreSQL service. Replication delay is the time it takes for a change made in the primary database to be replicated to the standby database. When the delay is abnormally high, it can indicate a problem with the replication process or the database itself. This can lead to data inconsistencies and other issues that can impact the performance and availability of the service. The incident usually requires investigation and troubleshooting to identify the root cause of the delay and to implement a solution to resolve the issue.


High replication delay in PostgreSQL service

```shell
# Environment Variables

export USERNAME="PLACEHOLDER"

export MASTER_SERVER="PLACEHOLDER"

export SLAVE_SERVER="PLACEHOLDER"

export SLAVE_MYSQL_SERVER_IP="PLACEHOLDER"

export MASTER_MYSQL_SERVER_IP="PLACEHOLDER"

```


### Check MySQL service status

```shell
systemctl status mysql
```

### Verify if replication is running and check its status

```shell
mysql -u ${USERNAME} -p -e "SHOW SLAVE STATUS\G"
```

### Check the log files of both the master and slave servers

```shell
tail -f /var/log/mysql/error.log
```

### Check the network connectivity and latency between the master and slave servers

```shell
ping ${MASTER_SERVER}

ping ${SLAVE_SERVER}

traceroute ${MASTER_SERVER}

traceroute ${SLAVE_SERVER}
```

### Check the load on the master server

```shell
top
```

### Check the MySQL configuration files on both servers

```shell
cat /etc/mysql/my.cnf
```

### Check the disk usage and available space on both servers

```shell
df -h
```

### Check the MySQL version and compare it on both servers

```shell
mysql -u ${USERNAME} -p -e "SELECT VERSION();"
```

### Measure the replication lag of a MySQL database

```shell
mysql -u ${USERNAME} -p -e "SHOW SLAVE STATUS\G" | grep Seconds_Behind_Master | awk '{print $2}'

```


### Define variables

```shell
MASTER_SERVER=${MASTER_MYSQL_SERVER_IP}

SLAVE_SERVER=${SLAVE_MYSQL_SERVER_IP}
```

### Check network connectivity

```shell
ping -c 3 $MASTER_SERVER > /dev/null 2>&1

if [ $? -eq 0 ]; then

    echo "Network connectivity between master and slave MySQL servers is OK."

else

    echo "Network connectivity between master and slave MySQL servers is not OK."

fi
```

### Check the configuration of the MySQL replication process and ensure that it is correctly set up.

```shell
bash

#!/bin/bash

# Stop the MySQL service

sudo systemctl stop mysql.service

# Backup the my.cnf file

sudo cp /etc/mysql/my.cnf /etc/mysql/my.cnf.bak

# Edit the my.cnf file

sudo sed -i 's/^server-id/#server-id/' /etc/mysql/my.cnf

sudo sed -i 's/^log_bin/#log_bin/' /etc/mysql/my.cnf

sudo sed -i 's/^binlog_do_db/#binlog_do_db/' /etc/mysql/my.cnf

sudo sed -i 's/^replicate_do_db/#replicate_do_db/' /etc/mysql/my.cnf

# Start the MySQL service

sudo systemctl start mysql.service

echo "MySQL replication configuration has been checked and updated."

```


MySQL Slave Replication Lag

Overview

Parameters

Debug

Check MySQL service status

Verify if replication is running and check its status

Check the log files of both the master and slave servers

Check the network connectivity and latency between the master and slave servers

Check the load on the master server

Check the MySQL configuration files on both servers

Check the disk usage and available space on both servers

Check the MySQL version and compare it on both servers

Measure the replication lag of a MySQL database

Repair

Define variables

Check network connectivity

Check the configuration of the MySQL replication process and ensure that it is correctly set up.

Learn more

Related Runbooks

SQL Server database not marked for replication sync.

Redis too many masters incident

Redis replication broken incident.

Redis disconnected slaves incident

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