JavaScript at the Edge

import { Image } from '@fly/image'

async function watermarkPicture() {
  const [picture, logo] = await Promise.all([
    loadImage(pictureURL),
    loadImage(logoURL)
  ])

  const meta = picture.metadata()

  const padPct = 0.1
  const padding = {
    top: parseInt(meta.height * padPct),
    bottom: parseInt(meta.height * padPct),
    left: parseInt(meta.width * padPct),

import proxy from '@fly/proxy'

// the Glitch App URL
const glitchHost = "fly-example.glitch.me"

// create a proxy fetch function to Glitch
const glitch = proxy(`https://${glitchHost}`,
  {
    headers: {
      'host': glitchHost, // set HOST header to glitchHost
      'x-forwarded-host': false // Don‘t send x-forwarded-host header
    }
  })

export default function balancer(backends: FetchFn[]) {
const tracked = backends.map((h) => {
  if (typeof h !== "function") {
    throw Error("Backend must be a fetch like function")
  }
  return <Backend>{
    proxy: h,
    requestCount: 0,
    scoredRequestCount: 0,
    statuses: Array<number>(10),
    lastError: 0,
    healthScore: 1,
    errorCount: 0