example.js

const logger = require('.');
const Koa = require('koa');
const compress = require('koa-compress')();
const app = new Koa();

// wrap subsequent middleware in a logger
app.use(logger());

// 204
app.use(function (ctx, next) {
  if (ctx.path === '/204') ctx.status = 204;
  else return next();
});

// 404
app.use(function (ctx, next) {
  if (ctx.path === '/404') return;
  return next();
});

// destroy
app.use(function (ctx, next) {
  if (ctx.path === '/close') return ctx.req.destroy();
  return next();
});

// compress the response 1/2 the time to calculate the stream length
app.use(function (ctx, next) {
  if (Math.random() > 0.5) {
    return next();
  }

  return compress(ctx, next);
});

// response middleware
app.use(function (ctx, next) {
  // yield control downstream
  next()
    .then(function () {
      // sleep for 0-2s
      return sleep((Math.random() * 2000) | 0);
    })
    .then(function () {
      // error
      if (Math.random() > 0.75) {
        const err = new Error('boom');
        err.status = 500;
        throw err;
      }

      // random body
      const body = new Array((Math.random() * 5 * 1024) | 9).join('a');
      ctx.status = 200;
      ctx.body = body;
    });
});

const port = process.env.PORT || 3000;
app.listen(port);
console.log('listening on port ' + port);

// sleep helper
function sleep(ms) {
  return new Promise(function (resolve) {
    setTimeout(resolve, ms);
  });
}