"After all, the engineers only needed to refuse to fix anything, and modern industry would grind to a halt." -Michael Lewis

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How to Publish and Subscribe to Redis Using Lettuce

Apr 2021

The source code for what follows can be found on Github.

Subscribing to topics in redis allows for a fanout behavior, where any number of subscribers can be notified of a message from a publisher.

With the cli, you can simply run:

redis-cli subscribe some-channel
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "some-channel"
3) (integer) 1

Then, in another terminal, we can:

redis-cli publish some-channel some-message
(integer) 1

And we will see in the original terminal where we're still subscribed:

1) "message"
2) "some-channel"
3) "some-message"

In java using lettuce, the process is pretty similar, but subscribing is a little wonky.

Publish/Subscribe with Lettuce

For a fast feedback loop, you can refer to either using embedded redis to test lettuce or using a redis test container to test lettuce as a starting point. Once that's in place, subscribing and publishing looks like this:

    public void publishAndSubscribe() throws Exception {
        StatefulRedisPubSubConnection<String, String> pubSubConnection =

        AtomicBoolean messageReceived = new AtomicBoolean(false);
        RedisPubSubReactiveCommands<String, String> reactivePubSubCommands = pubSubConnection.reactive();

                .doOnNext(stringStringChannelMessage -> messageReceived.set(true))


                .publish("some-channel", "some-message")



The gist of the code is that we publish to the channel after we subscribe, and verify that we actually received a message by asserting that an AtomicBoolean was flipped to true. This test passes.

Nick Fisher is a software engineer in the Pacific Northwest. He focuses on building highly scalable and maintainable backend systems.