Upgrade Impact: During the upgrade, the MQTT console and each service node in the cluster may experience a second-level flash (the flash time is positively related to the cluster scale). The client application needs to set automatic reconnection to avoid affecting the business. During the upgrade period, there may be a small number of failures in message sending, and the application should implement a retry mechanism for disconnection failures; at the same time, there may be message delays. For administrative operations on the console, please avoid maintenance windows. Sorry for the inconvenience caused to you, if you have any questions, please feel free to contact us through the ticket.