Consistency Issue?

[erich-team]

I'm not entirely sure this is an issue, with either dynamoid or dynamodb or just just an issue with how I'm approaching this. So, I'm posting this here instead of as an issue.

The Background

Given the models

class ParentClass
  include SubmissionPackage::Builder
  table
  field :url, :string
  field :full_response, :map, default: {}
end

class ChildClass
  def response=(data)
    self.url=data[:secure_url]
    super(data)
  end

   def call_external_system
     #calls some external system with a callback url supplied by us
   end

   after_create :call_external_system
  def enqueue_evaluate_response
      #enqueue a job to do something the the response and URL
  end
end

I instantiate ChildClass which kicks off what is likely the familiar process of calling an external system to do some work and call back in our system with the response. (ChildClass#call_external_system).

class ResponsesController
  def create
    child_object = ChildClass.find(params[:id])
    child_object.full_response =  params[:response]
    child_object.save
    child_object.enqueue_evaluate_response
  end
end

ChildClass#full_response is called, #url is set, #full_response is set, the object is persisted and #enqueue_evaluate_response is called, kicking off a job where something is done with URL and the response.

class SomeJob<ApplicationJob
  def perform(child_object)
    puts child_object.url
  end
end

This is a pattern I've used hundreds of times in this application.

The callback into the system usually takes place on the order minutes after ChildClass is initially instantiated.

The Complication

Put simply #url and #full_response are always nil inside SomeJob, even, if SomeJob later. Not surprisingly the values in #attributes and #attributes_before_type_case are also nil. I have checked the AWS console and URL is populated.

To further complicate matters:

SomeClass.find('asdf', consistent_read: true).attributes_before_type_cast[:full_response] # NOT NILL
SomeClass.find('asdf', consistent_read: true).attributes_before_type_cast[:url] # NIL

Similarly

SomeClass.find('asdf', consistent_read: true).attributes[:full_response] # NOT NILL
SomeClass.find('asdf', consistent_read: true).attributes[:url] # NIL

Lastly

SomeClass.consistent.find(:id=>'asdf').first.attributes[:full_response] # NIL
SomeClass.consistent.find(:id=>'asdf').first.attributes[:url] # NIL
SomeClass.consistent.find(:id=>'asdf').first.attributes_before_type_cast[:full_response] # NIL
SomeClass.consistent.find(:id=>'asdf').first.attributes_before_type_cast[:url] # NIL

The Conclusion

I'm crazy. Or I'm confused. Or there's a bug. Keep in mind, the DynamoDB console shows all the data being there.

[andrykonchin]

Could you please provide some minimal but still complete code examples to reproduce the issue? Right now it isn't clear what is an expected result in your examples.

[erich-team]

In trying to (a) obscure business logic of our application and (b) simplify the examples, I have probably overshot which is made worse by being an entirely asynchronous affair.

In essence, hours after the last create or update, reading a model from dynamodb still returns nil for #urlfield, even when forcing consistent read.

But let me see if I can put together something with a bit more meat.

[andrykonchin]

As far as I understand in your example some attribute (url) is present in an item in a DynamoDB table but somehow after loading Dynamoid model this field is nil. Am I right?

So could you please provide an example to reproduce the issue:

• item from a DynamoDB table
• and model class declaration

If url field is declared in a model (with field declaration) and item in a table has this attribute - it should be available in a model as well. If it isn't - it's definitely a bug.