Connection pools and multiplexing

Manage Redis connections efficiently

Redis example code generally opens a connection, demonstrates a command or feature, and then closes. Real-world code typically has short bursts of communication with the server and periods of inactivity in between. Opening and closing connections involves some overhead and leads to inefficiency if you do it frequently. This means that you can improve the performance of production code by making as few separate connections as possible.

Managing connections in your own code can be tricky, so the Redis client libraries give you some help. The two basic approaches to connection management are called connection pooling and multiplexing. The redis-py, jedis, and go-redis clients support connection pooling, while NRedisStack supports multiplexing. Lettuce supports both approaches.

Connection pooling

When you initialize a connection pool, the client opens a small number of connections and adds them to the pool.

Each time you "open" a connection from the pool, the client returns one of these existing connections and notes the fact that it is in use.

When you later "close" the connection, the client puts it back into the pool of available connections without actually closing it.

If all connections in the pool are in use but the app needs more, then the client can simply open new connections as necessary. In this way, the client eventually finds the right number of connections to satisfy your app's demands.

Multiplexing

Instead of pooling several connections, a multiplexer keeps a single connection open and uses it for all traffic between the client and the server. The "connections" returned to your code are used to identify where to send the response data from your commands.

Note that it is not a problem if the multiplexer receives several commands close together in time. When this happens, the multiplexer can often combine the commands into a pipeline, which improves efficiency.

Multiplexing offers high efficiency but works transparently without requiring any special code to enable it in your app. The main disadvantage of multiplexing compared to connection pooling is that it can't support the blocking "pop" commands (such as BLPOP) since these would stall the connection for all callers.