[Rails] Re: ActiveRecord::Base.transaction - SystemStackError - stack level too deep:

On Saturday, 22 June 2013 16:06:54 UTC-7, Bob O wrote:

Im having an issue that seems to only happen when trying to use a transaction. Ive used transactions many times in the past and Im at a loss as to why im getting the stack level too deep problem.

SystemStackError - stack level too deep:

  actionpack (3.2.13) lib/action_dispatch/middleware/reloader.rb:70:in `'

I have a StackOveflow with more detail - http://stackoverflow.com/q/16930511/1408461

As stated in the SO. If I try to save the record to the database outside the transaction it saves just fine. I only get the error in the transaction. 

Params Object

params => {    "resource"=> {      "resource_type"=>"document",       "resource_name"=>"My Rails Doc",      "source_id"=>"Dropbox"    },    "resource_document"=> {      "resource_document"=> #<ActionDispatch::Http::UploadedFile:0x007f8e919d06f8        @content_type="text/plain",        @headers= "Content-Disposition:           form-data; name=\"resource_document[resource_document]\";          filename=\"rails_local_env_setup.txt\"\r\n          Content-Type: text/plain\r\n",        @original_filename="rails_local_env_setup.txt",        @tempfile= #<File:/var/folders/t4/lfmj7mhj52b2krryzh7dj4hh0000gn/T/RackMultipart20130604-29589-2c0seo>>},      "action"=>"create",    "controller"=>"resources"   }

**Controller**

def create      if current_teacher      @resource = ResourceObject.create_teacher_resource(params, current_teacher)    end      if current_student      @resource = ResourceObject.create_student_resource(params, current_student)    end      if current_admin      @resource = Resource.new(params[:resource])    end      respond_to do |format|      if @resource.success        format.html { redirect_to @resource, notice: 'Resource was successfully created.' }        format.json { render json: @resource, status: :created, location: @resource }      else        format.html { render action: "new" }        format.json { render json: @resource.errors, status: :unprocessable_entity }      end    end  end
**Transaction**
class ResourceObject      def self.create_teacher_resource(params, teacher)      begin        ActiveRecord::Base.transaction do          # Create Resource          @resource = Resource.new          @resource.resource_name = params[:resource][:resource_name]          @resource.resource_type = params[:resource][:resource_type]          @resource.source_id = params[:resource][:source_id]          @resource.teacher_id = teacher.id          @resource.save            # Create Resource Document          @resource_document = ResourceDocument.new          @resource_document.resource_document = params[:resource_document][:resource_document]          @resource_document.resource_id = @resource.id          @resource_document.save            # TODO Add Commom Core Joins          # TODO Video Uploader          # TODO Image Uploader            return @resource.success = "ok"        end          rescue Exception => e

A style note here: rescuing Exception is not typically what you want. See this for more details:

http://stackoverflow.com/questions/10048173/why-is-it-bad-style-to-rescue-exception-e-in-ruby

 

        # TODO Need to figure out how to pass exception message back to controller            return @resource.errors          end             end      end
end
Resource Model

class Resource < ActiveRecord::Base    	include TransactionAttributes  

I'd be curious as to what's in this module - it could be relevant...

 

    attr_accessible :resource_name, :resource_type, :source_id, :teacher_id, :student_id, :success, :errors

 :errors here is not useful - attr_accessible controls mass-assignment of attributes (as when you do Resource.new(:param1 => 'foo', :param2 => 'bar'). You almost certainly do not want to mass-assign an internal part of ActiveRecord. :)

  belongs_to :teacher, :class_name => "Teacher", :foreign_key => "teacher_id"    belongs_to :student, :class_name => "Student", :foreign_key => "student_id"

Another minor (not terribly relevant) style note: :class_name and :foreign_key are both redundant here, as the values specified are the same as the ActiveRecord defaults. 

Next steps for debugging this:

- it would be useful to see the code for the TransactionAttributes module you're including. Perhaps something is hitting an internal method and making a mess.

- showing the DB schema would help as well; again, having fields with names that clash with ActiveRecord's can cause peculiar behavior.

- a full stack trace might shed some light; especially in the case of StackLevelTooDeep, the final line isn't always helpful.

--Matt Jones

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