error handling in asynchronous node.js calls

Question

I\'m new to node.js although I\'m pretty familiar with JavaScript in general. My question is regarding \"best practices\" on how to handle errors in node.js.

Normall

Answer 1

I give an answer to my own question... :)

As it seems there is no way around to manually catch errors. I now use a helper function that itself returns a function containing a try/catch block. Additionally, my own web server class checks if either the request handling function calls response.end() or the try/catch helper function waitfor() (raising an exception otherwise). This avoids to a great extent that request are mistakenly left unprotected by the developer. It isn't a 100% error-prone solution but works well enough for me.

handler.waitfor = function(callback) {
  var me=this;

  // avoid exception because response.end() won't be called immediately:
  this.waiting=true;

  return function() {
    me.waiting=false;
    try {
      callback.apply(this, arguments);

      if (!me.waiting && !me.finished)
        throw new Error("Response handler returned and did neither send a "+
          "response nor did it call waitfor()");

    } catch (e) {
      me.handleException(e);
    }
  }
}

This way I just have to add a inline waitfor() call to be on the safe side.

function handleRequest(request, response, handler) {
  fs.read(fd, buffer, 0, 10, null, handler.waitfor(
    function(error, bytesRead, buffer) {

      buffer.unknownFunction();  // causes exception
      response.end(buffer);
    }
  )); //fs.read
}

The actual checking mechanism is a little more complex, but it should be clear how it works. If someone is interested I can post the full code here.