Subscriber-publisher model is considered essential feature of Redis that unlocks the door to a wide variety of use cases and components. Redis’s subscription capabilities allow users to subscribe to a certn “channel”, to receive messages when any other user publishes a message to that channel.
It’s most useful when you’re dealing with a large number of clients that need to stay up-to-date with changes made anywhere else in the system. Rather than having to continuously query the database itself, they can simply have Redis push updates to them while they wt.
Publishing to one of these channels is pretty strghtforward. All that’s needed is a redis client and a simple command:
PUBLISH channel-name message-string
When this command is sent, Redis will push out the contents of the string to any client that has subscribed to that channel. Subscribing to a channel is just as easy, and requires two steps:
1. Establish a subscription connection:
`SUBSCRIBE channel-name`
The Redis server will acknowledge the command and wt for incoming messages.
2. Register a handler for incoming messages
`ON MESSAGE channel-name HANDLER`
This command will register a callback with the server, which will be called whenever a message is published to that channel. This callback should be a function that accepts two arguments: the channel name and the message payload.
It’s also possible to have multiple channels open at the same time, allowing your application to listen in on multiple message streams simultaneously.
Redis’s pub/sub model is one of the most useful features in the database and can be used to build powerful, real-time applications. With just a few simple commands, you can unlock the door for your app to keep up-to-date with any changes made throughout the system.
