Resque.enqueue failing on second run

Question

I am trying to port an app from Rails 3.0.3 to Rails 3.1rc... I don't think I've missed out anything, in terms of configuration. The process works perfectly in Rails 3.0.X and not in 3.1rc.

In console, I do:

Resque.enqueue(EncodeSong, Song.find(20).id, Song.find(20).unencoded_url)

Everything works so far. Resque-web reports no failed jobs. And, I get the two 'puts' from module EncodeSong.

However, running Resque.enqueue(EncodeSong, Song.find(20).id, Song.find(20).unencoded_url) a second time will return the following error in resque-web (below). To make the error go away, I would have to close the process thats running: QUEUE=* rake environment resque:work and rerun it in the console window. But the problem comes back after trying to Resque.enqueue() after the first time.

Class
    EncodeSong
Arguments

    20
    "https://bucket_name.s3.amazonaws.com/unencoded/users/1/songs/test.mp3"

Exception
    PGError
Error
    server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request.

    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:272:in `exec'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:272:in `block in clear_cache!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:271:in `each_value'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:271:in `clear_cache!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/postgresql_adapter.rb:299:in `disconnect!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_pool.rb:191:in `block in disconnect!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in `each'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in `disconnect!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activesupport-3.1.0.rc1/lib/active_support/core_ext/module/synchronization.rb:35:in `block in disconnect_with_synchronization!'
    /Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activesupport-3.1.0.rc1/lib/active_support/core_ext/module/synchronization.rb:34:in `disconnect_with_synchronization!'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_pool.rb:407:in `remove_connection'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_specification.rb:116:in `remove_connection'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_specification.rb:79:in `establish_connection'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_specification.rb:60:in `establish_connection'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/activerecord-3.1.0.rc1/lib/active_record/connection_adapters/abstract/connection_specification.rb:55:in `establish_connection'
    /Users/Chris/Sites/site_name/lib/tasks/resque.rake:17:in `block (2 levels) in <top (required)>'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:355:in `call'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:355:in `run_hook'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:162:in `perform'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:130:in `block in work'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:116:in `loop'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/worker.rb:116:in `work'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/resque-1.16.1/lib/resque/tasks.rb:27:in `block (2 levels) in <top (required)>'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:205:in `call'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:205:in `block in execute'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:200:in `each'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:200:in `execute'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
    /Users/Chris/.rvm/rubies/ruby-1.9.2-p136/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:151:in `invoke_with_call_chain'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/task.rb:144:in `invoke'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:112:in `invoke_task'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:90:in `block (2 levels) in top_level'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:90:in `each'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:90:in `block in top_level'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:129:in `standard_exception_handling'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:84:in `top_level'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:62:in `block in run'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:129:in `standard_exception_handling'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/lib/rake/application.rb:59:in `run'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/gems/rake-0.9.0/bin/rake:31:in `<top (required)>'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/bin/rake:19:in `load'
    /Users/Chris/.rvm/gems/ruby-1.9.2-p136@railspre/bin/rake:19:in `<main>'

Here is the rest of my relevant code:

/config/initializers/resque.rb

require 'resque'

uri = URI.parse(APP_CONFIG['redis_to_go_url'])
Resque.redis = Redis.new(:host => uri.host, :port => uri.port, :password => uri.password)

# Load all jobs at /app/jobs
Dir["#{Rails.root}/app/jobs/*.rb"].each { |file| require file }

/app/jobs/encode_song.rb

module EncodeSong
  @queue = :encode_song

  def self.perform(media_id, s3_file_url)
    begin
      media = Song.find(media_id)
      puts 'foo11111'
      puts media.id
    rescue
      puts "Error #{$!}"
    end
  end
end

lib/tasks/resque.rake

require 'resque/tasks'

task "resque:setup" => :environment do
  ENV['QUEUE'] = '*'

  # ONLY on Heroku, since they are still running PostgreSql 8 on their shared plan.
  # This block of code is not needed on PostgreSql 9, as tested on local environment.
  # Issue: My best guess is that master resque process establishes connection to db,
  # while loading rails app classes, models, etc, and that connection becomes corrupted
  # in fork()ed process (on exit?). Possible fix is to reestablish the connection the AR
  # after a Resque fork.
  Resque.after_fork do |job|
    ActiveRecord::Base.establish_connection
  end

end

desc "Alias for resque:work (To run workers on Heroku)"
task "jobs:work" => "resque:work"

Not very sure, but it may be somewhat related to this issue. My guess is that master resque process establishes connection to db, while loading rails app classes, models, etc, and that connection becomes corrupted in fork()ed process (on exit?).

Any help / direction will be appreciated.

EDIT:

If I remove the following block from lib/tasks/resque.rake:

  Resque.after_fork do |job|
    ActiveRecord::Base.establish_connection
  end

And in console, run Resque.enqueue(EncodeSong, Song.find(20).id, Song.find(20).unencoded_url)

I get a new error (in console where QUEUE=* rake environment resque:work was run):

Error PGError: ERROR:  prepared statement "a3" already exists
: SELECT  "songs".* FROM "songs"  WHERE "songs"."id" = $1 LIMIT 1

It seems, this may be a bug with the adapter? Could be wrong here. Your thoughts?

Answer 1

This has solved it for me:

require 'resque/tasks'

task "resque:setup" => :environment do
  ENV['QUEUE'] = '*'

  Resque.before_fork = Proc.new { ActiveRecord::Base.establish_connection }
end

Source: carhartl comment on Github