How to resolve deserialization error in delayed job?

Question

I am trying to use DelayedJob and the job is failing, giving the following error in the database:

{Delayed::DeserializationError
/Library/Ruby/Gems/1.8/gems/delayed_j         


        

Answer 1

Sometimes when we upgrade libs delayed jobs still keep old references.

Try to find the id of delayed_job in logs and play to parse its handler to ruby to find the wrong reference

j = DelayedJob.find(XXX)
data = YAML.load_dj(j.handler)
data.to_ruby

I made a pull request to help with this problem.

Meanwhile you can use this lines

# config/initializers/delayed_job.rb

# Monkey patch to use old class references
module Psych

  class << self; attr_accessor :old_class_references end
  @old_class_references = {}

  class ClassLoader
    private

    def find klassname
      klassname = ::Psych.old_class_references[klassname] || klassname
      @cache[klassname] ||= resolve(klassname)
    end
  end

  module Visitors
    class ToRuby < Psych::Visitors::Visitor
      def revive klass, node
        if klass.is_a? String
          klassname = ::Psych.old_class_references[klass] || klass
          klass = Kernel.const_get(klassname) rescue klassname
        end
        s = register(node, klass.allocate)
        init_with(s, revive_hash({}, node), node)
      end
    end
  end
end

# Add all old dependencies (hash keys) pointing to new references (hash values)
Psych.old_class_references = {
  'ActiveRecord::AttributeSet' => 'ActiveModel::AttributeSet'
  # ...
}