In a recent technical article, Slack explains how its real-time messaging framework works. Here is my short summary:
A Slack message travels through five important servers:
- • WebApp: defines the API that a Slack client could use
- • Admin Server (AS): finds the correct Channel Server using channel ID
- • Channel Server (CS): maintains the history of message channel
- • Gateway Server (GS): deployed in each geographic region. Maintain WebSocket channel subscription
- • Envoy: service proxy for cloud-native applications
- • Because there are too many channels, the Channel Server (CS) uses consistent hashing to allocate millions of channels to many channel servers.
- • Slack messages are delivered through WebApp and Admin Server to the correct Channel Server.
- • Through Gate Server and Envoy (a proxy), the Channel Server will push messages to message receivers.
- • Message receivers use WebSocket, which is a bi-directional messaging mechanism, so they are able to receive updates in real-time.
