What is Redis Pub/Sub used for?

Redis Pub/Sub implements the messaging system where the senders (in redis terminology called publishers) sends the messages while the receivers (subscribers) receive them. The link by which the messages are transferred is called channel. In Redis, a client can subscribe any number of channels.

Why do we need pub sub?

Pub/Sub makes discovery of services easier, more natural and less error prone. Instead of maintaining a roster of peers that an application can send messages to, a publisher will simply post messages to a topic. Then, any interested party will subscribe its endpoint to the topic, and start receiving these messages.

How Redis Pub/Sub works internally?

When a client sends a SUBSCRIBE command, its client object gets added to the set of clients for that channel name. To PUBLISH , Redis looks up the subscribers in the pubsub_channels map, and for each client, it schedules a job to send the published message to the client’s socket.

Is Redis Pub/Sub push or pull?

Pub/Sub is synchronous communication (push protocol). All parties need to be active at the same time to be able to communicate. Here Redis is a pure synchronous messaging broker.

What is pub/sub channel?

A Publish-Subscribe Channel works like this: It has one input channel that splits into multiple output channels, one for each subscriber. When an event is published into the channel, the Publish-Subscribe Channel delivers a copy of the message to each of the output channels.

What means pub sub?

Publish/subscribe messaging
Publish/subscribe messaging, or pub/sub messaging, is a form of asynchronous service-to-service communication used in serverless and microservices architectures. In a pub/sub model, any message published to a topic is immediately received by all of the subscribers to the topic.

Is Redis pub/sub blocking?

Redis’ pub/sub sends messages to clients subscribed (listening) on a channel. If you are not listening, you will miss the message (hence the blocking call). If you want to have it non-blocking, I recommend using a queue instead (redis is pretty good at that too).

When should you not use a pub sub?

Synchronous point-to-point communication between the two endpoints is the best solution for media streaming. Pub/Sub is not suitable for carrying VoIP or video telephony traffic over the Internet.