node-redis: fetchSockets() call to sendCommand() needs update for cluster client

[winchell]

Versions:

Node: 18.15.0
socket.io: 4.6.1
socket/redis-adapter: 8.1.0
redis: 4.6.5
Redis Cluster: 7.0.5

import { createAdapter } from "@socket.io/redis-adapter"
const redis = createCluster(cluster_opts);
const redis_pub_client = redis.duplicate()
const redis_sub_client = redis.duplicate()
await Promise.all([redis.connect(), redis_pub_client.connect(), redis_sub_client.connect()])
io.adapter(createAdapter(redis_pub_client, redis_sub_client));
...
const sockets = await io.fetchSockets();

Socket communication works as expected but a call to fetchSockets() crashes. Am I misusing this?

Error:

/project/node_modules/@redis/client/dist/lib/client/RESP2/encoder.js:6
    let strings = '*' + args.length + CRLF;
                             ^

TypeError: Cannot read properties of undefined (reading 'length')
    at encodeCommand (/project/node_modules/@redis/client/dist/lib/client/RESP2/encoder.js:6:30)
    at RedisCommandsQueue.getCommandToSend (/project/node_modules/@redis/client/dist/lib/client/commands-queue.js:138:45)
    at Commander._RedisClient_tick (/project/node_modules/@redis/client/dist/lib/client/index.js:507:76)
    at Commander._RedisClient_sendCommand (/project/node_modules/@redis/client/dist/lib/client/index.js:494:82)
    at Commander.sendCommand (/project/node_modules/@redis/client/dist/lib/client/index.js:196:100)
    at /project/node_modules/@redis/client/dist/lib/cluster/index.js:129:148
    at Commander._RedisCluster_execute (/project/node_modules/@redis/client/dist/lib/cluster/index.js:221:26)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

Seems to be landing on this https://github.com/socketio/socket.io-redis-adapter/blob/main/lib/index.ts#L918

return this.pubClient
        .sendCommand(["pubsub", "numsub", this.requestChannel])
        .then((res) => parseInt(res[1], 10));

Historically the problem was node-redis didn't support cluster PubSub. It does support it now - redis/node-redis#2373 as of 4.6.1.

However the issue now is that socket.io-redis-adapter doesn't fully support the createCluster client because fetchSockets() ends up calling sendCommand() and the createCluster client has a different function signature there. It's sendCommand(firstKey, isReadonly, args, options) as opposed to sendCommand(args, options).

[darrachequesne]

Released in 8.2.0. Thanks 👍