README.md

polished-load-balancer

polished-load-balancer is a simple load balancer for a single Shiny app.

• it runs several instances of your Shiny app to overcome the single-process limitation of a standard shiny app
• new Shiny app instances are automatically started and stopped as your app experiences more and less traffic
• it is a middleware for a Node.js Express application, so it can be easily extended

Installation

npm install polished-load-balancer

Simple Example

The following example will serve a Shiny app located in the /srv/shiny_app folder:

# server.js
import express from 'express'
import polishedLoadBalancer from 'polished-load-balancer'

const plb = await polishedLoadBalancer({
  appDir: "/srv/shiny_app",
  maxSessions: 1
})

const app = express()

app.use(plb)

app.listen(8080)

If you run the above server using node server.js, your auto scaling Shiny app will be available at http://localhost:8080.

Options

The load balancer middleware is created by polishedLoadBalancer(options). options is an object with the following configurable properties:

• appDir: string - the path of the folder containing the Shiny app.

• maxSessions: integer > 0 - the max number of active sessions per Shiny app instance before starting up a new Shiny app instance. New Shiny app instances are automatically scaled up and down as each running Shiny app reaches this maxSessions number of sessions.

Prior Work

This package was adapted from node-shiny-proxy by Martin Vergier