Use Async Library with MongoDB using Nodejs

Question

When I make an API call, I want to update 2 separate collections with MongoDB. The official way of thing this will be using transactions but because this is a prototype for now, I will just use 2 separate function calls to update each collection.

Here is what I am doing:

 async.waterfall([
    function(callback) {
        callback(null);
    }, function(callback) {
       connectToDatabase(MONGODB_URI)
      .then(db => updateDocument1(arguments))
      .then(result => {
        callback(null);
      });
    }
    , function(callback) {
       connectToDatabase(MONGODB_URI)
      .then(db => updateDocument2(arguments))
      .then(result => {
        callback(null);
      });
    , function(err, result) {
       callback(null, null)
    }
  ])

But somehow, it does not execute updateDocument2. Also, updateDocument1 stops in the middle of the process, so none of documents are updated. Do you know why? And Does anyone know a better way?

Saurabh Mistry · Accepted Answer · 2019-06-06 07:25:41Z

1

async parallel : do function execution parallelly without dependent of other function

async series : do function execution in series (one by one)

async waterfall : do first function execution then pass output of first function as input to next function

now in your case : if updating two collection not depending on each other you can use async parallel

answered Jun 6, 2019 at 7:25

Saurabh Mistry

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2 Comments

Matt Choi Over a year ago

even i do parellel, none gets executed because the function prematurely exits. I am using AWS Lambda

Saurabh Mistry Over a year ago

add console log and make sure you are getting results from database

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