Question about lettuce pub / sub connection subscriber mode

[brido4125]

https://redis.github.io/lettuce/ha-sharding/#connection-count-for-a-redis-cluster-connection-object
Above docs said Default Connection handling key-less cmd and pub / sub cmd.

I sent subscribe command first and waited the result of subscribe future result.
After that sent the key-less command, client-info.

public class SubMain {

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        RedisURI uri1 = RedisURI.Builder
                .redis("ncp-4c4-000", 6379)
                .build();

        RedisURI uri2 = RedisURI.Builder
                .redis("ncp-4c4-001", 6379)
                .build();

        RedisURI uri3 = RedisURI.Builder
                .redis("ncp-4c4-002", 6379)
                .build();


        RedisPubSubAdapter<String, String> adapter = new RedisPubSubAdapter<>() {
            @Override
            public void message(String channel, String message) {
                System.out.println("MSG Thread.currentThread().getName() = " + Thread.currentThread().getName());
                System.out.println(message);
            }
        };


        RedisClusterClient client1 = RedisClusterClient.create(Arrays.asList(uri1, uri2, uri3));
        StatefulRedisClusterPubSubConnection<String, String> conn1 = client1.connectPubSub();
        conn1.addListener(adapter);
        RedisClusterPubSubAsyncCommands<String, String> cmd1 = conn1.async();
        cmd1.subscribe("my-topic").get();
        String s = cmd1.clientInfo().get();
        System.out.println("s = " + s);
        Thread.sleep(1000);
    }
}

I thought subscribe command change the default connection to subscriber-mode.
So I expect client-info(key-less command) command will be failed.
But the result of client-info operation looks like proper.

s = id=224217 addr=x.x.x.x:54585 laddr=x.x.x.x:6379 fd=14 name= age=0 idle=0 flags=P db=0 sub=1 psub=0 ssub=0 multi=-1 qbuf=26 qbuf-free=20448 argv-mem=10 multi-mem=0 rbs=16384 rbp=47 obl=0 oll=0 omem=0 tot-mem=37842 events=r cmd=client|info user=default redir=-1 resp=3 lib-name=Lettuce lib-ver=6.3.2.RELEASE/8941aea

In Lettuce, how can handle situation like above?

[tishun]

Depends on the protocol version that you are using.

Lettuce uses RESP3 by default, and RESP3 allows a single connection to be used for both subscriptions and issuing of commands.
RESP2 on the other hand does not and requires a dedicated connection for subscriptions.

Does that help?

[brido4125]

thank you for rapid reply.

Does that help?

it was very helpful.
I recommanded another helpful docs for someone who want to understand relationship between RESP3 and pub/sub.

• https://github.com/redis/redis-specifications/blob/master/protocol/RESP3.md#push-type
• https://redis.io/docs/latest/develop/interact/pubsub/

[brido4125]

I have another question.

If lettuce using RESP3 and redis cache server supports it, default connection is created(or using)?

[tishun]

Apologies, not really sure what the question is, can you rephrase?

[brido4125]

I'm sorry about to confuse you.

I've been thinking about it, and I think I asked the wrong question.

[tishun]

No worries :)