All 7 Pub/Sub questions
More in Pub/Sub
What is the Redis Pub/Sub feature, and how does it let different parts of an application communicate? What is pattern based subscription using PSUBSCRIBE, and how does it differ from subscribing to specific individual channels? What happens to a message published on a channel if there are currently no subscribers listening to that channel? How do you check how many subscribers are currently listening to a specific channel in Redis? How would you design a real time notification system using Pub/Sub while working around its lack of guaranteed message delivery? How does Redis Pub/Sub behave differently in a Redis Cluster environment compared to a single instance setup?
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Redis › Pub/Sub

How do you subscribe to and publish messages on a specific Redis channel?

Beginner

Answer

You use the SUBSCRIBE command with a channel name to start listening for messages on that channel, and the PUBLISH command with a channel name and message content from a different client to send a message that all current subscribers of that channel will immediately receive.
SUBSCRIBE weather_updates
PUBLISH weather_updates 'Storm warning issued for the area'
Real-world example A weather alert system publishes severe weather warnings to a dedicated channel, instantly notifying every subscribed application or device that is currently listening for updates.

Common follow-ups: What happens to a client's subscription if it disconnects and reconnects?;Can you unsubscribe from a channel without disconnecting entirely?

Keyspace Notifications;Redis as a Message Queue
All 7 Pub/Sub questions