---
id: 0e04eaa1-7600-463e-bb14-6d6b3be95041
---

# MySQL Slave IO thread not running incident on Kubernetes.
---

MySQL Slave IO thread not running incident refers to a situation where the IO thread on a MySQL slave server is not running. This results in the slave server not being able to receive updates from the master server, leading to a replication delay that can cause data inconsistencies and other issues. This type of incident requires immediate attention to ensure that the replication process is resumed to prevent data loss and ensure system stability.

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

export MYSQL_SERVICE_NAME="PLACEHOLDER"

export MYSQL_CONTAINER_NAME="PLACEHOLDER"

export MYSQL_PASSWORD="PLACEHOLDER"

export NAMESPACE="PLACEHOLDER"

export MASTER_POD_NAME="PLACEHOLDER"

export SLAVE_POD_NAME="PLACEHOLDER"
```

## Debug

### Get the list of all MySQL pods
```shell
kubectl get pods -l app=mysql
```

### Check the logs of the MySQL pod to see if there are any errors related to the IO thread
```shell
kubectl logs ${MYSQL_POD_NAME} | grep "IO thread"
```

### Check the status of the MySQL replication process
```shell
kubectl exec ${MYSQL_POD_NAME} -- mysql -e "SHOW SLAVE STATUS\G"
```

### Check if the MySQL service is running
```shell
kubectl get svc ${MYSQL_SERVICE_NAME}
```

### Check if the MySQL configuration is correct
```shell
kubectl exec ${MYSQL_POD_NAME} -- mysql --verbose --help | grep "server-id"
```

### Check the resource utilization of the pod
```shell
kubectl top pod ${MYSQL_POD_NAME}
```

### Check if the pod is running on a node with sufficient resources
```shell
kubectl describe pod ${MYSQL_POD_NAME} | grep "Node:"
```

### Check the events related to the pod
```shell
kubectl describe pod ${MYSQL_POD_NAME} | grep "Events"
```

### Network connectivity issue between the master and slave databases.
```shell


#!/bin/bash



# Set the namespace and pod names

NAMESPACE=${NAMESPACE}

MASTER_POD=${MASTER_POD_NAME}

SLAVE_POD=${SLAVE_POD_NAME}



# Check if the master and slave pods are running

MASTER_STATUS=$(kubectl get pods -n $NAMESPACE $MASTER_POD -o jsonpath='{.status.phase}')

SLAVE_STATUS=$(kubectl get pods -n $NAMESPACE $SLAVE_POD -o jsonpath='{.status.phase}')



if [[ $MASTER_STATUS != "Running" ]]; then

    echo "Error: Master pod is not running."

    exit 1

fi



if [[ $SLAVE_STATUS != "Running" ]]; then

    echo "Error: Slave pod is not running."

    exit 1

fi



# Check if the master and slave pods are in the same network

MASTER_IP=$(kubectl get pod -n $NAMESPACE $MASTER_POD -o jsonpath='{.status.podIP}')

SLAVE_IP=$(kubectl get pod -n $NAMESPACE $SLAVE_POD -o jsonpath='{.status.podIP}')



if [[ $MASTER_IP == $SLAVE_IP ]]; then

    echo "Error: Master and slave pods are on the same IP address."

    exit 1

fi



# Check the network connectivity between the master and slave pods

nc -w 5 -z $MASTER_IP 3306

if [[ $? -ne 0 ]]; then

    echo "Error: Unable to connect to the master database."

    exit 1

fi



nc -w 5 -z $SLAVE_IP 3306

if [[ $? -ne 0 ]]; then

    echo "Error: Unable to connect to the slave database."

    exit 1

fi



echo "Network connectivity between the master and slave databases is OK."

exit 0


```

## Repair

### Restart the MySQL Slave IO thread on the affected instance.
```shell


#!/bin/bash



# Set the name of the Kubernetes pod and container running MySQL

POD_NAME=${MYSQL_POD_NAME}

CONTAINER_NAME=${MYSQL_CONTAINER_NAME}



# Restart the MySQL Slave IO thread

kubectl exec $POD_NAME -c $CONTAINER_NAME -- /usr/bin/mysql -uroot -p${MYSQL_PASSWORD} -e "STOP SLAVE IO_THREAD; START SLAVE IO_THREAD;"


```


MySQL Slave IO thread not running incident refers to a situation where the IO thread on a MySQL slave server is not running. This results in the slave server not being able to receive updates from the master server, leading to a replication delay that can cause data inconsistencies and other issues. This type of incident requires immediate attention to ensure that the replication process is resumed to prevent data loss and ensure system stability.


This incident type typically occurs in distributed computing systems, where Spark tasks are experiencing high disk I/O and shuffle spills. Spark is a popular distributed computing engine that uses shuffle operations to move data between nodes in a cluster, which can sometimes result in performance issues due to spills. The spills occur when the data being shuffled exceeds the memory capacity allocated for the shuffle operations. This incident requires optimization of the shuffle operations to reduce spills and improve overall performance.


Spark tasks experiencing shuffle spills and high disk I/O.

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.

The Redis missing master incident occurs when the Redis cluster has no node marked as master. This can cause problems with the Redis service and may result in service disruptions or failures. It is important to address this issue promptly to ensure the smooth operation of the Redis service.


Redis missing master incident

```shell
export MYSQL_POD_NAME="PLACEHOLDER"

export MYSQL_SERVICE_NAME="PLACEHOLDER"

export MYSQL_CONTAINER_NAME="PLACEHOLDER"

export MYSQL_PASSWORD="PLACEHOLDER"

export NAMESPACE="PLACEHOLDER"

export MASTER_POD_NAME="PLACEHOLDER"

export SLAVE_POD_NAME="PLACEHOLDER"
```


### Get the list of all MySQL pods

```shell
kubectl get pods -l app=mysql
```

### Check the logs of the MySQL pod to see if there are any errors related to the IO thread

```shell
kubectl logs ${MYSQL_POD_NAME} | grep "IO thread"
```

### Check the status of the MySQL replication process

```shell
kubectl exec ${MYSQL_POD_NAME} -- mysql -e "SHOW SLAVE STATUS\G"
```

### Check if the MySQL service is running

```shell
kubectl get svc ${MYSQL_SERVICE_NAME}
```

### Check if the MySQL configuration is correct

```shell
kubectl exec ${MYSQL_POD_NAME} -- mysql --verbose --help | grep "server-id"
```

### Check the resource utilization of the pod

```shell
kubectl top pod ${MYSQL_POD_NAME}
```

### Check if the pod is running on a node with sufficient resources

```shell
kubectl describe pod ${MYSQL_POD_NAME} | grep "Node:"
```

### Check the events related to the pod

```shell
kubectl describe pod ${MYSQL_POD_NAME} | grep "Events"
```

### Network connectivity issue between the master and slave databases.

```shell


#!/bin/bash



# Set the namespace and pod names

NAMESPACE=${NAMESPACE}

MASTER_POD=${MASTER_POD_NAME}

SLAVE_POD=${SLAVE_POD_NAME}



# Check if the master and slave pods are running

MASTER_STATUS=$(kubectl get pods -n $NAMESPACE $MASTER_POD -o jsonpath='{.status.phase}')

SLAVE_STATUS=$(kubectl get pods -n $NAMESPACE $SLAVE_POD -o jsonpath='{.status.phase}')



if [[ $MASTER_STATUS != "Running" ]]; then

    echo "Error: Master pod is not running."

    exit 1

fi



if [[ $SLAVE_STATUS != "Running" ]]; then

    echo "Error: Slave pod is not running."

    exit 1

fi



# Check if the master and slave pods are in the same network

MASTER_IP=$(kubectl get pod -n $NAMESPACE $MASTER_POD -o jsonpath='{.status.podIP}')

SLAVE_IP=$(kubectl get pod -n $NAMESPACE $SLAVE_POD -o jsonpath='{.status.podIP}')



if [[ $MASTER_IP == $SLAVE_IP ]]; then

    echo "Error: Master and slave pods are on the same IP address."

    exit 1

fi



# Check the network connectivity between the master and slave pods

nc -w 5 -z $MASTER_IP 3306

if [[ $? -ne 0 ]]; then

    echo "Error: Unable to connect to the master database."

    exit 1

fi



nc -w 5 -z $SLAVE_IP 3306

if [[ $? -ne 0 ]]; then

    echo "Error: Unable to connect to the slave database."

    exit 1

fi



echo "Network connectivity between the master and slave databases is OK."

exit 0


```


### Restart the MySQL Slave IO thread on the affected instance.

```shell


#!/bin/bash



# Set the name of the Kubernetes pod and container running MySQL

POD_NAME=${MYSQL_POD_NAME}

CONTAINER_NAME=${MYSQL_CONTAINER_NAME}



# Restart the MySQL Slave IO thread

kubectl exec $POD_NAME -c $CONTAINER_NAME -- /usr/bin/mysql -uroot -p${MYSQL_PASSWORD} -e "STOP SLAVE IO_THREAD; START SLAVE IO_THREAD;"


```


MySQL Slave IO thread not running incident on Kubernetes.

Overview

Parameters

Debug

Get the list of all MySQL pods

Check the status of the MySQL replication process

Check if the MySQL service is running

Check if the MySQL configuration is correct

Check the resource utilization of the pod

Check if the pod is running on a node with sufficient resources

Network connectivity issue between the master and slave databases.

Repair

Restart the MySQL Slave IO thread on the affected instance.

Learn more

Related Runbooks

Spark tasks experiencing shuffle spills and high disk I/O.

SQL Server database not marked for replication sync.

Redis too many masters incident

Redis replication broken incident.

Support