Smart client handoffs

Learn how to avoid disruptions during Redis server maintenance.

Smart client handoffs (SCH) is a feature of Redis Cloud and Redis Enterprise servers that lets them actively notify clients about planned server maintenance shortly before it happens. This lets a client reconnect or otherwise respond gracefully without significant interruptions in service.

SCH is primarily useful when server software or hardware upgrades are required. It provides two main features to help the client avoid disruptions in service during the maintenance period:

• Relaxed timeouts: Upgrades tend to impact the general performance of the server. Advance notification of the upgrade lets a client adjust its command timeouts to take this into account and avoid aborting commands too soon.
• Transparent reconnection: Upgrades also involve migrating Redis shards to new nodes, which inevitably disconnects clients from existing nodes. However, with some advance warning of the disconnection, a client can buffer commands, connect to a new node, and then resume the buffered commands without aborting any of them. As a result, users see no disruption in service.

Enable SCH

SCH is enabled by default on Redis Cloud, but you must enable it explicitly on Redis Enterprise servers by using the v1/cluster REST API request to set the client_maint_notifications option to true. The example below shows how to do this using the curl command line utility:

curl -k -X PUT -H "accept: application/json" \
 -H "content-type: application/json" \
 -u "[email protected]:test123" \
 -d '{ "client_maint_notifications": true }' \
 https://localhost:9443/v1/cluster

SCH is enabled automatically on the client side during connection if you select the RESP3 protocol, which is a requirement for SCH. However, you can configure some parameters, such as the timeouts to use during maintenance. See the pages linked below to learn how to configure SCH for:

• redis-py
• node-redis
• Lettuce
• go-redis