koa2-skeleton-app.js

#!/usr/bin/env node
// Refer to: https://github.com/saadq/koa2-skeleton for more

if(process.env.NODE_ENV === "production")
{
    require("newrelic")
}

import {install} from "source-map-support"
install()
import cluster from "cluster"
import os from "os"
import Promise from "bluebird"
import config from "./config/default.json"
import pkg from "./package.json"

import Koa from "koa"
import views from "koa-views"
import helmet from "koa-helmet"
import serve from "koa-static"
import compress from "koa-compress"
import bodyParser from "koa-bodyparser"

import index from "./routes/index"

const app = new Koa()
app.name = pkg.description
app.proxy = true

/* Begin Middleware */

// Error Handler
app.use(async (ctx, next) =>
{
    try
    {
        await next()
    }

    catch(error)
    {
        ctx.status = error.status || 500
        ctx.body =
        {
            message: error.showMessage && error.message ? error.message : "Internal Server Error."
        }
    }
})

// CORS Handler
app.use((ctx, next) =>
{
    ctx.set("Access-Control-Allow-Origin", "*")
    ctx.set("Access-Control-Allow-Methods", "GET,HEAD,PUT,POST,DELETE")
    return Promise.resolve(next())
})

// Secure Headers
app.use(helmet())

// Static Handler
app.use(serve(`./public`))

// Compression Handler
app.use(compress())

// Body Parser Handler
app.use(bodyParser(
{
    onerror: (error, ctx) =>
    {
        ctx.status = 422
        ctx.body =
        {
            message: "Unable to parse request body."
        }
    }
}))

// Views Handler
app.use(views("./views",
{
    map:
    {
        html: "lodash"
    }
}))

/* End Middleware */

/* Begin Routes */

app.use(index.routes())

// 404 Handler
app.use((ctx, next) =>
{
    if(ctx.status === 404) 
    {
        ctx.body =
        {
            message: "Resource Not Found."
        }   
    }
})

// End Routes

// Clustering
if(cluster.isMaster)
{
    os.cpus().forEach(() => cluster.fork())

    cluster.on("online", worker => console.log(`Worker ${worker.process.pid} online.`))
    cluster.on("message", message => console.log(message))
    cluster.on("exit", (worker, signal) =>
    {
        console.log(`Worker ${worker.process.pid} died (signal: ${signal}). Restarting...`)
        cluster.fork()
    })
}

else
{
    app.listen(config.port, () => console.log(`Listening on http://127.0.0.1:${config.port}`))
}