Following is the JSON data I am trying to load using ember-data:
{
  "product" : [
    { 
        "id" : 1,
        "name" : "product1",
        "master" : {
            "id" : 1,
            "name" : "product1",
            "images" : [
                {
                    "id" : 1,
                    "productUrl" : "/images/product1_1.jpg"
                },
                {
                    "id" : 2,
                    "productUrl" : "/images/product1_2.jpg"
                }
            ]
        }
    },
    { 
        "id" : 2,
        "name" : "product2",
        "master" : {
            "id" : 2,
            "name" : "product2",
            "images" : [
                {
                    "id" : 3,
                    "productUrl" : "/images/product2_1.jpg"
                },
                {
                    "id" : 4,
                    "productUrl" : "/images/product2_2.jpg"
                }
            ]
        }
    }
]
}   
The models are as follows:
App.Product = DS.Model.extend
  name: DS.attr('string')
  description: DS.attr('string')
  master: DS.belongsTo('master')
App.Master = DS.Model.extend
  images: DS.hasMany('image')
App.Image = DS.Model.extend
  productUrl: DS.attr('string')
The Application Serializer code is as follows:
App.ApplicationSerializer = DS.ActiveModelSerializer.extend(DS.EmbeddedRecordsMixin,
attrs: {
  images: { embedded : 'always' }
  master: { embedded : 'always' }
}
)
The problem is that the "master" model records are being returned empty. I am not sure, where I am going wrong.
I am using the following platform configuration: 
ember-source (1.4.0)
ember-data-source (1.0.0.beta.7)
ember-rails (0.15.0)
Rails (4.1.0)
Thanks