#Master-Slave Switch Exception

#Problem Description

An exception occurs during master-slave switching in the PostgreSQL cluster, which may lead to:

• Extended switching time
• Data inconsistency
• Service interruption

#Common Causes

1. Network partition
2. Storage performance issues
3. Misconfigured settings
4. Insufficient resources

#Troubleshooting Steps

#1. Check Cluster Status

kubectl get postgresql <cluster-name> -o yaml

Key fields to pay attention to:

• status.PostgresClusterStatus
• status.master
• status.pods

#2. View Patroni Logs

kubectl logs <pod-name> -c patroni

Key logs to review:

• Leader election process
• Fault detection information
• Switching timestamps

#3. Check Replication Status

kubectl exec -it <pod-name> -c postgres -- psql -c "\x" -c "select * from pg_stat_replication;"

Key fields to pay attention to:

• state
• sync_state
• replay_lag

#4. Verify Network Connection

kubectl exec -it <pod-name> -c postgres -- ping <other-node-IP>

#Solutions

#Network Issues

1. Check network policy configuration
2. Validate communication between nodes
3. Optimize network performance

#Storage Issues

1. Check storage performance metrics
2. Optimize I/O configuration
3. Upgrade storage hardware

#Configuration Optimization

1. Adjust Patroni parameters:
   • ttl
   • loop_wait
   • retry_timeout
2. Optimize PostgreSQL configuration:
   • wal_keep_segments
   • max_wal_senders

#Resource Shortage

1. Increase CPU and memory resources
2. Optimize query performance
3. Scale out cluster nodes

#Preventive Measures

1. Regularly test failover
2. Monitor cluster health status
3. Optimize resource configuration
4. Configure reasonable alert thresholds