Redis Clustered Pubsub Delayed SSubscribe triggers MOVE error.

[CR7273868]

Redis or Redis GO does not go well with Clustered PUBSUB of Redis

Expected Behavior

Redis GO works even when using the same PUBSUB pointer to subscribe to other channels later on.

Current Behavior

Redis GO does SSubscribe, but then if u do one later one let's say in a goroutine. It says MOVED to another IP or PORT. And doesn't receive the messages at all, afterwards.

Possible Solution

Keep track of shards where what comes from. Fred from Redis RS provides a way to see what shard channel a server was bound to. Per message u'd receive, you could see which server it was hooked too, if I am not wrong.

FRED RS

Steps to Reproduce

package main

import (
	"context"
	"log"
	"time"

	"github.com/redis/go-redis/v9"
)

func main() {
	client := redis.NewClusterClient(&redis.ClusterOptions{
		Addrs: []string{"masked:7000"},
	})

	client_2 := redis.NewClusterClient(&redis.ClusterOptions{
		Addrs: []string{"masked:7000"},
	})

	pubsub := client.SSubscribe(context.Background(), "mychannel")
	defer pubsub.Close()

	go func() {
		// Subscribe to a channel
		time.Sleep(2 * time.Second)
		if err := pubsub.SSubscribe(context.Background(), "mychannel2"); err != nil {
			panic(err)
		}
		log.Println("Subscribed to mychannel2")
	}()
	go func() {
		ticker := time.NewTicker(1 * time.Second)
		for range ticker.C {
			// Channel 2 does not work when ssubscribing later
			client_2.SPublish(context.Background(), "mychannel2", "hello")
			// Does work since we subscribed when we started the program
			client.SPublish(context.Background(), "mychannel", "hello")
		}
	}()
	for {
		msg, err := pubsub.ReceiveMessage(context.Background())
		if err != nil {
			log.Println("ERROR", err)
			continue
		}
		log.Println(msg.Channel, msg.Payload)
	}

}

Output log:

2024/09/01 07:31:00 mychannel hello
2024/09/01 07:31:01 Subscribed to mychannel2
2024/09/01 07:31:01 ERROR MOVED 4312 masked:7002
2024/09/01 07:31:01 mychannel hello
2024/09/01 07:31:02 mychannel hello
2024/09/01 07:31:03 mychannel hello
2024/09/01 07:31:04 mychannel hello
2024/09/01 07:31:05 mychannel hello
2024/09/01 07:31:06 mychannel hello

All you need is a Redis Cluster and use SSUBSCRIBE and have it move across redis nodes to replicate this issue. I have tried several cluster setups correctly, but keep running into this issue. I assume IOREDIS from Node.JS has this exact same issue. The only that works is Fred from Redis which I actively use.

Context (Environment)

4 servers: Each has 3 master coupled with slave to each master. Granting 12 masters coupled with 12 slaves.
Each server is compiled with Redis:

Redis server v=7.2.5 sha=00000000:0 malloc=jemalloc-5.3.0 bits=64 build=b5c2f37750637637

Making Redis PUBSUB work correctly, without having to deal with weird issues like moving and it goes out of scope

Redis Clustered PUBSUB doesn't work after subscribing later on.

[akshaykhairmode]

I am facing a similar challenge, the ssubscribe call done later does not give any error and no data is received by it.

We rolled back to using global pubsub for now. We are using elasticache redis v7+ for the server.

[ndyakov]

@CR7273868, @akshaykhairmode I assume you are using SSubscribe with channels for different slots. At least this is what was done in the example above. Here is the documentation:

• https://redis.io/docs/latest/commands/ssubscribe/ it states that you can use one subscription for multiple channels when they are from the same slots. Since the ones in the example won't be from the same slot, this is why the example is failing for you.