Websockets and scalability
Am a beginner with websockets. Have a need in my application where server needs to notify clients when something changes and am planning to use websockets.
1) Single server instance and single client ==> How many websockets will be created and how many connections to websockets?
2) Single server instance and 10 clients ==> How many websockets will be created and how many connections to websockets?
3) Single server instance and 1000 clients ==> How many websockets will be created and how many connections to websockets?
How do you scale with webscokets when your application has a 1000’s of user base?
Thanks much for your feedback.
Answer
1) Single server instance and single client ==> How many websockets will be created and how many connections to websockets?
If your client creates one webSocket connection, then that's what there will be one webSocket connection on the client and one on the server. It's the client that creates webSocket connections to the server so it is the client that determines how many there will be. If it creates 3, then there will be 3. If it creates 1, then there will be 1. Usually, the client would just create 1.
2) Single server instance and 10 clients ==> How many websockets will be created and how many connections to websockets?
As described above, it depends upon what the client does. If each client creates 1 webSocket connection and there are 10 clients connected to the server, then the server will see a total of 10 webSocket connections.
3) Single server instance and 1000 clients ==> How many websockets will be created and how many connections to websockets?
Same as point #2.
How do you scale with webscokets when your application has a 1000’s of user base?
A single server, configured appropriately can handle hundreds of thousands of simultaneous webSocket connections that are mostly idle since an idle webSocket uses pretty much no server CPU. For even larger scale deployments, one can cluster the server (run multiple server processes) and use sticky load balancing to spread the load.
There are many other articles like these on Google worth reading if you're pursuing large scale webSocket or socket.io deployments:
The Road to 2 Million Websocket Connections in Phoenix
600k concurrent websocket connections on AWS using Node.js
10 million concurrent webSockets
Ultimately, the achievable scale per a properly configured server will likely have more to do with how much activity there is per connection and how much computation is needed to deliver that.