redis-streams-adapter: receives events but room emits don’t reach clients

[bakikucukcakiroglu]

What I’m seeing

When I use @socket.io/redis-streams-adapter with ioredis, the server receives events from clients, but emits to rooms (within a namespace) often don’t reach clients.

If I switch to the classic @socket.io/redis-adapter, everything works immediately with the same code.

I’m currently running only one Socket.IO server process locally (no sticky sessions / no load balancer).

Versions

• socket.io: 4.8.3
• @socket.io/redis-streams-adapter: ^0.2.3
• ioredis: ^5.9.2

Server setup

import http from "http";
import { Server } from "socket.io";
import { createAdapter } from "@socket.io/redis-streams-adapter";
import { Redis } from "ioredis";

const server = http.createServer();

const redis = new Redis({
  host: process.env.REDIS_HOST, // redis-*****.europe-west3-1.gce.cloud.redislabs.com
  port: Number(process.env.REDIS_PORT), // e.g. 16937
  username: process.env.REDIS_USER || "default",
  password: process.env.REDIS_PASS,
});

const io = new Server(server, {
  path: "/v1/api/socket.io",
  cors: { origin: "*" },
  adapter: createAdapter(redis),
});

io.of("/chatbot").on("connection", (socket) => {
  socket.on("join", async ({ customerId }) => {
    await socket.join(customerId);
    socket.emit("joined", { customerId });
  });

  socket.on("visitor-message", ({ customerId, message }) => {
    // ✅ server receives this event
    console.log("received visitor-message", { customerId, message });

    // ❌ these emits do NOT reach clients when redis-streams-adapter is enabled
    io.of("/chatbot").to(customerId).emit("visitor-message-broadcast", { customerId, message });
    io.of("/dashboard").to("shop:demo").emit("visitor-message-broadcast", { customerId, message });
  });
});

io.of("/dashboard").on("connection", (socket) => {
  socket.on("join", async ({ shop }) => {
    await socket.join(`shop:${shop}`);
    socket.emit("joined", { shop });
  });
});

server.listen(3000, () => console.log("listening on :3000"));

Expected behavior

• After a socket joins a room, namespace.to(room).emit(...) should deliver events to all clients in that room.
• This should work in a single-node setup too.

Actual behavior

• Server receives events, but the room emits above don’t arrive at clients (same namespace + cross-namespace).
• Replacing the adapter with @socket.io/redis-adapter makes everything work.

Possibly related: CORS error only when using redis-streams-adapter

When using the streams adapter, I also sometimes see this in the browser:

Access to XMLHttpRequest at 'https://.../v1/api/socket.io/?EIO=4&transport=polling...'
from origin 'https://...' has been blocked by CORS policy:
No 'Access-Control-Allow-Origin' header is present on the requested resource.

Not sure if this is a separate issue, but it only appeared while testing with redis-streams-adapter.

Additional note

I also tried to make redis-streams-adapter work with node-redis, but when I enabled the adapter, my HTTP server stopped responding (I might have misconfigured it). Switching to ioredis allowed the server to run, but emits still don’t work as described above. Switching to the classic Redis adapter works immediately.

[darrachequesne]

Hi! This might happen if the connection to Redis is not established, as the client will retry publishing to the stream (this is not the case for the @socket.io/redis-adapter adapter, which will fail and return directly).

Are you sure the redis client is connected? You can check with await redis.connect().

Regarding:

Access to XMLHttpRequest at 'https://.../v1/api/socket.io/?EIO=4&transport=polling...'
from origin 'https://...' has been blocked by CORS policy:
No 'Access-Control-Allow-Origin' header is present on the requested resource.

This means that the client is not able to reach the server. Maybe it's offline? Or a proxy in front of your server might be misconfigured?

Reference: https://socket.io/docs/v4/troubleshooting-connection-issues/