title: Mongoose - multiple collection parallel document creation
body: <p>I am running into a problem when I create documents for different collections. Here the last callback attached to create(...) for each model(corresponding to a collection) is to drop the respective collection but it is not working consistently.</p>
  
  <p>e.g. We have 3 models A, B and C.</p>
  
  <pre><code>db.once('open',function(){
  
  A.create({
  
  ...
  
  },function(err,doc){
  
  db.collection('a').drop();
  
  });
  
  B.create({
  
  ...
  
  },function(err,doc){
  
  db.collection('b').drop();
  
  });
  
  C.create({
  
  ...
  
  },function(err,doc){
  
  db.collection('c').drop();
  
  });
  
  }
  </code></pre>
  
  <p>All the 3 collections do not get dropped every time.</p>
  
  <p>What could be the reason?</p>