Example using the async-state module

server.js

var http = require('http')
var asyncState = require('async-state')

process.on('uncaughtException', function (err) {
  if (asyncState.req) {
    console.log('An error occurred while processing request for', asyncState.req.url)
  } else {
    console.log('An error occurred outside of an HTTP request')
  }
})

http.createServer(function (req, res) {
  // when ever an HTTP request is received, we call an async function that
  // takes a long time to finish. The async function unfortunately have a
  // bug so that it thorws an Error after 10 seconds.
  //
  // Multiple HTTP requests can be active when the error occurrs, so we
  // use asyncState to keep track of which HTTP request that fail.
  
  asyncState.req = req

  doWork(function () {
    res.end()
  })
}).listen(3000)

// async-state doesn't leak state between different async call stacks,
// so when doWork fails in 20 seconds it will not have access to any
// requests that might have arrived prior to the callback being called
setTimeout(doWork, 10000)

// Async function taking 10 seconds to finish
function doWork (cb) {
  console.log('Preparing to do hard work...')

  setTimeout(function () {
    throw new Error('Bang!')
  }, 10000)
}