feat(redis): support Redis Cluster via comma separated seed nodes - #1318
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feat(redis): support Redis Cluster via comma separated seed nodes#1318bakiburakogun wants to merge 1 commit into
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The README recommends Redis for multi-node websocket deployments, but the client is built with createClient(), which does not follow MOVED redirections. Pointed at a Redis Cluster it connects and then fails roughly half of all operations at run time, depending on which slot a key hashes to. Treat a comma separated REDIS_URL as a list of cluster seed nodes and build a cluster client from it. Credentials given on the first seed are applied to the nodes discovered afterwards, since cluster discovery reports them without auth. A single URL keeps its existing behaviour. Signed-off-by: Baki Burak Öğün <63836730+bakiburakogun@users.noreply.github.com>
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Fixes #1317
Summary
RedisAdapter.createRedisClient()builds a single-node client withcreateClient(), which does not followMOVEDredirections. Pointed at a Redis Cluster it connects successfully, the Socket.IO Redis Streams adapter sets up, and then roughly half of all operations fail at run time depending on which slot a key hashes to — a silent, partial failure rather than a clean one.This treats a comma separated
REDIS_URLas a list of cluster seed nodes:A single URL behaves exactly as before.
createCluster()comes from theredispackage already independencies, so there is no new requirement.Credentials given on the first seed are passed as cluster
defaults, because cluster discovery reports the remaining nodes without auth and they would otherwise be rejected.Testing
Against a 3-master / 3-replica cluster on a Debian 12 host, writing 40 keys:
createClient()pointed at one node (before)MOVED 8308 127.0.0.1:7002createCluster()with three seeds (after)Reads afterwards returned 40/40.
I also ran the real websocket server from this branch against that cluster, with
STORAGE_STRATEGY=redisand three seeds, and connected two Socket.IO clients with valid JWTs to the same board. Both receivedinit-room,room-user-changeanduser-joinedfor each other, so room state and the Streams adapter both work through the cluster client.One rough edge I did not fix
With a cluster client, the first command issued before the slot map is loaded throws rather than being queued, and I saw exactly one such error at startup:
It happened once, did not recur, and nothing downstream was affected — the server served boards normally afterwards. The cause is that
ServerServicestarts the connection without awaiting it (this.redisClient.connect().catch(...)), which a single-node client tolerates because it queues commands. Making startup await the connection would fix it properly, but that changes the constructor's shape, so I left it out of this PR rather than restructure startup on your behalf. Happy to follow up with that if you would like it.Note for administrators
Redis Cluster only has database 0, so the
/database_numbersuffix cannot be used to separate whiteboard keys from other users of the same cluster. I mentioned this in the README next to the cluster example.