Resque workers fail immediately: undefined method `write' for nil:NilClass - ruby-on-rails

Question

I am using Resque (and resque-scheduler) in my Rails app to run a recurring job. This was working fine for me, until today. I made some code changes, which I thought were unrelated, but now every worker fails before the perform method is even entered (checked with a debug statement). The same worker method works fine when I run it in the rails console. It only fails via resque on the development localhost (Postgres DB).
The error shown in the resque console for the failed worker is:
Exception
NoMethodError
Error
undefined method `write' for nil:NilClass
There is no additional stack trace for the error. Any idea why this is failing?
Additional info:
lib/tasks/resque.rake
# Resque tasks
require 'resque/tasks'
require 'resque_scheduler/tasks'
namespace :resque do
task :setup do
require 'resque'
require 'resque_scheduler'
require 'resque/scheduler'
# you probably already have this somewhere
Resque.redis = 'localhost:6379'
# If you want to be able to dynamically change the schedule,
# uncomment this line. A dynamic schedule can be updated via the
# Resque::Scheduler.set_schedule (and remove_schedule) methods.
# When dynamic is set to true, the scheduler process looks for
# schedule changes and applies them on the fly.
# Note: This feature is only available in >=2.0.0.
#Resque::Scheduler.dynamic = true
# The schedule doesn't need to be stored in a YAML, it just needs to
# be a hash. YAML is usually the easiest.
Resque.schedule = YAML.load_file("#{Rails.root}/config/resque_schedule.yml")
# If your schedule already has +queue+ set for each job, you don't
# need to require your jobs. This can be an advantage since it's
# less code that resque-scheduler needs to know about. But in a small
# project, it's usually easier to just include you job classes here.
# So, something like this:
# require 'jobs'
end
end
task "resque:setup" => :environment do
#ENV['QUEUE'] = '*'
Resque.before_fork = Proc.new { ActiveRecord::Base.establish_connection }
end
config/resque.yml
development: localhost:6379
test: localhost:6379:1
staging: redis1.se.github.com:6379
fi: localhost:6379
production: redis1.ae.github.com:6379
initializers/resque.rb
rails_root = Rails.root || File.dirname(__FILE__) + '/../..'
rails_env = Rails.env || 'development'
resque_config = YAML.load_file(rails_root.to_s + '/config/resque.yml')
Resque.redis = resque_config[rails_env]
# This will make the tabs show up.
require 'resque_scheduler'
require 'resque_scheduler/server'
config/resque_schedule.yml
populate_game_data:
# you can use rufus-scheduler "every" syntax in place of cron if you prefer
every: 1m
# By default the job name (hash key) will be taken as worker class name.
# If you want to have a different job name and class name, provide the 'class' option
class: PopulateDataWorker
queue: high
args:
description: "This job populates the game and data"
Should note that the above files were not changed between working and non-working state.

Answer 1

We had the same issue this morning, and we pinned it down to a gem update by New Relic.
Version 3.5.6.46 of newrelic_rpm was yanked on rubygems, but it was somehow installed by bundle update.
They are still on the beta track for 3.5.6 and had some issues with Resque. See https://github.com/newrelic/rpm/commit/e81889c2bce97574ec682dafee12015e13ccb2e1
The fix was to add '~> 3.5.5.38' in our Gemfile for newrelic_rpm