What does Proxy mean for Azure SignalR service?

Question

This documentation about Azure SignalR talks about Azure SignalR is a proxy.

My questions are:

1. What is meant by Proxy and Backplane?
2. Is http2 an equivalent technology for SignalR where the real time web can be done with http2?

Answer 1

1. The service being a proxy basically means that it manages all of the client connections for you so you don't have to use a backplane to keep track of connected clients and which servers they are currently connected to yourself.

   Let's say that you have an application that you want to scale out by adding more servers to handle an increased number of client connections. The problem with scaling out is that each server only knows about its own client connections. It's unaware of connections to the other servers in the farm. This means that a message that you intend to send to all clients only goes out to the clients that are connected to the particular server that your hub is sending the message from.

   Using a backplane component, each server sends all messages to the backplane instead of sending them directly to its connected clients. The backplane is then responsible for forwarding the messages to the other servers.

2. HTTP/2 is not a replacement for web sockets and which one you should use depends on your requirements.