How to do proper error handling in node with domain?

Question

I am using a third party library. Which is using node domain for error handling. If the callback function passed to that third party library have any error, It end-up in calling my callback multiple times.

Example code is:

var startFunction = function (callback) {
  //Call thirdParty function and wait for response
  thirdPartyFunction(function (error, data) {
    console.log("Called with");
    console.log(arguments);
    //Assume there is an error in my callback function
    setTimeout(function () {
      dd
      callback.apply(null);
    }, 2000);
  });
}
 //ThirdParty function don't modify anything here
var thirdPartyFunction = function (callback) {
  var Domain = require("domain");
  var d = require('domain').create();
  d.on('error', function (er) {
    console.log("hi");
    callback.apply(null, er);
  });
  d.run(function () {
    setTimeout(function () {
      callback.apply(null, [null, "Hello"]);
    }, 1000);
  });
};
startFunction(function () {
  console.log("Got response")
});

We reported this bug to third party lib and they have modified the source code. Like:

d.on('error', function (er) {
  if (isCalled == false) {
    isCalled = true;
  } else {
    return;
  }
  console.log("hi");
  callback.apply(null, er);
});

Now problem of function getting called multiple times is solved. But final callback is never getting called.

How to handle this behavior of node ?

If third party lib modify there code to, It result in application crash. Putting a wrapper domain also not help.

d.on('error', function (er) {
  if (isCalled == false) {
    isCalled = true;
  } else {
    throw new Error("Getting called");
    return;
  }
  console.log("hi");
  callback.apply(null, er);
});

What is the best method of handing such cases in node ?

Why isCalled fix did not work? Where is it set? Isnt it set when a callback is called? — Murukesh, Jun 21 '15 at 16:30

score 1 · Answer 1 · answered Sep 17 '13 at 20:02

You can attach your own domain listener to your callback function like so:

    var startFunction = function (callback) {
  //Call thirdParty function and wait for response
  thirdPartyFunction(function (error, data) {
    var d1 = require('domain').create();
    d1.on('error', function(er){
      console.log("bye");
      callback.apply(null, er);
    });
    d1.run(function () {
      console.log("Called with");
      console.log(arguments);
      //Assume there is an error in my callback function
      setTimeout(function () {
        dd
        callback.apply(null);
      }, 2000);
  });
    })
}

This way if there is an error it will be caught by your handler and the error will be sent back up to the main level and not get caught in the infinite loop.

How to do proper error handling in node with domain?

1 Answers1