How to send data streams via WebSocket?

Question

Java

Good afternoon.
Share your experience on how to solve this problem:

There is a server, there are 5 thousand data streams. Let's say each thread is just a number that changes periodically. That is, there are 5 thousand numbers, each of which changes periodically.

There are 1 million users (customers, say, mob applications). Each client wants to subscribe (via WebSocket or otherwise) to some data stream.

That is, for each data stream, there are 200-1000 subscribers.

If we take an understandable analogy, then this is like a server with quotes that are constantly changing, and thousands of applications that receive quotes from this server.

Question: how to make such a server? Is there something ready? I have never encountered such a number of connections, and in general, the task seems not difficult - I got a new number, sent it to 1000 connections, but there are doubts that it will work quickly.

Somewhere I read that Netty holds a huge number of creations without problems - is that so?

Answer 1

Yes, it's true about Netty. Only it is very low-level, it is better to take Spring WebFlux or Play Framework.

Answer 2

This is already akin to multicasts (iptv), where most of the load lies on the transport (switches) and not on the soft side.

Answer 3

Based on recent experience, I would suggest to raise several servers with Swoole (write in PHP and not Java) For example, 200k connections per each (with white IPs).
DNS round robin : One name points to multiple IPs and hopefully spreads connections evenly. Or hide behind a load balancer, but then each network interface will accept a smaller number of connections, no more than 65k in theory, less in practice.
Use Redis as a PubSub broker. From each server, subscribe to messages from Redis.
When a WebSocket client connects, its subscriptions are stored in the Memory Table of the server it connected to. Key$fdconnections, keep 1/0 for each of the 1000 channels in the columns, or simply list the channel numbers through a separator in a single string field.
When a message arrives (a new number in one of the subscriptions), loop through the table (all connections of this server) and send a message to those who have this subscription enabled.