CODEWITHSUNDEEP
javascriptnode.jsasynchronousexpressmongoose
bob_cobb
bob_cobb

Reputation: 2269

Waterfall method for async.js hanging when calling mongoose save method

I'm trying to use the async waterfall method but when it gets to one of the functions, it hangs. I suspect it's because the save() operation is too slow for the execution context, but that's why I was starting to use async's waterfall, so I can wait for the value returned until it goes to the next function in the series (passing along the proper data with it which would be the counted in my case below).

// In my user controller:

async.waterfall([
  function(callback) {
    getSubmission(id, function(submission) {
      if (submission) {
        callback(null, submission);
      }
    });
  },
  function(submission, callback) {
    var submissionId = submission._id;

    getViews(submissionId, ip, function(count) {
      if (count) {
        callback(null, count, submissionId);
      }
    });
  },
  // Those top two functions work perfectly passing what
  // I need to this one which is where I'm having trouble
  function(views, submissionId, callback) {
    // addView is called because it is actually
    // inserting a row in the db, but never returns from the caller
      addView(submissionId, ip, function(added) {
        // this callback doesn't fire
        if (added) {
          callback(null, added);
        }
      });
  },
  function(added, callback) {
    console.log(added);
  }
 ]);

This is what addView() is (also within user controller which is where the previous async.waterfall code also is in) :

var addView = function(submissionId, ip, callback) {
  Submission.addView({
    submissionId : submissionId,
    ip: ip
  }, function(err, counted) {
    if (err) {
      throw err;
    }

    if (counted) {
      callback(counted);
    }
  });
};

This is what it's calling (inside my Submission model file) when it calls Submission.addView():

exports.addView = function(obj, fn) {
  var ip = obj.ip,
      submissionId = obj.submissionId,
      submissionView = new SubmissionView(obj);
// it gets to this point

  submissionView.save({
    ip : ip,
    submission_id : submissionId
  }, function(err, counted) {
    fn(err, counted);
  });
};

Upvotes: 1

Views: 1452

Answers (1)

AndyD
AndyD

Reputation: 5385

Whenever async "hangs", it's usually because a callback hasn't been called.

You need to make sure that you call the callback in all code paths. I would also recommend that you reserve the first parameter of any async callback to be an error, even if you don't use it as that is the pattern used throughout node.js. Some modules rely on this pattern. e.g. domains.

If you make the below change, then I would expect some error to pop up somewhere:

getSubmission(id, function(submission) {
      if (submission) {
        callback(null, submission);
      }
    });

should be something like this:

getSubmission(id, function(err, submission) {
      if(err){
        return callback(err);
      }
      if (!submission) {
        return callback('no submission found');
      }
      callback(null, submission);
    });

Upvotes: 4

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