go-hermes-prototype

README

Hermes

Purpose

Hermes is an asynchronous pub-sub messaging system that uses the Websocket protocol to talk to its HTTP clients. It's meant to be used as a lightweight self-hosted replacement for Pusher.

Configuration

The following environment variables are recognised by the Go application:

Variable	Mandatory	Default
HERMES_HTTP_PORT	no	8000
HERMES_NATS_URL	no	nats://localhost:4222
HERMES_WEBSOCKET_TIMEOUT	no	15m
HERMES_LOGGING_LEVEL	no	info

Dependencies

• Websockets: https://github.com/gobwas/ws
• NATS client: https://github.com/nats-io/go-nats

Design

A NATS server has to run first for Hermes to work. Hermes uses NATS to handle the pub-sub functionality.

Hermes exposes an HTTP server that serves two routes:

• /subscribe - clients can use it to initiate a websocket connection via HTTP GET and request subscription to mesages with a given "subject"
• /publish - backend services can send messages to it via HTTP POST requests, which contain a query parameter subj that specifies the NATS "subject". Subsequently, Hermes will broadcast the received message to the clients that are subscribed to this "subject"