Module: Resque::Plugins::AccessWorkerFromJob

Defined in:
lib/resque/plugins/access_worker_from_job.rb

Overview

Adds a Resque plugin to allow jobs to access the worker running them via a cleverly-named worker instance variable. Purpose: this allows jobs to access shared sockets in the parent worker.

Be careful to note that each job forks before running, however, so instance variables will be a COPY and, if changed, their changes won’t persist into the next job’s perform method. However, since sockets ARE persisted, this allows multiple jobs to share a single persistent socket kept alive in the worker.

To use, add 

extend Resque::Plugins::AccessWorkerFromJob

to the BOTTOM of the class with the perform method (the extend line must come AFTER the perform method has already been defined, or else the alias method will fail). Now your perform method can reference a worker attribute.

As additional functionality, this plugin can also abort a job gracefully if it’s picked up by the wrong worker class, which is useful if you’ve subclassed Resque::Worker to add your own functionality and need to ensure your jobs aren’t accidentally run against the original superclass. Note that if your job is picked up by the wrong class it’ll be removed from the queue, though – this provides a way to avoid messy exceptions, but it’s still your responsibility to make sure you keep your queues + worker classes straight.

To implement this additional requiring-certain-worker-class feature, add 

self.required_worker_class = 'ClassName'

as well.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#required_worker_class ⇒ Object

Returns the value of attribute required_worker_class.



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# File 'lib/resque/plugins/access_worker_from_job.rb', line 47

def required_worker_class
  @required_worker_class
end

#worker ⇒ Object

Returns the value of attribute worker.



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# File 'lib/resque/plugins/access_worker_from_job.rb', line 47

def worker
  @worker
end

Class Method Details

.extended(base) ⇒ Object 



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# File 'lib/resque/plugins/access_worker_from_job.rb', line 49

def self.extended(base)
  unless base.methods.include?('perform') || base.methods.include?(:perform)
    raise %Q{You must call "extend Resque::Plugins::AccessWorkerFromJob" AFTER (below) defining the perform method}
  end
  
  class << base
    def wants_worker_access
      true
    end
    
    # Remove worker from last argument, so can write their perform method assuming just the arguments
    # they sent it, without worrying about the appended worker.
    def perform_with_worker_in_arguments(*args)
      args.pop if args.last.is_a?(::Resque::Worker)
      perform_without_modified_arguments( *args )
    end

    alias_method :perform_without_modified_arguments, :perform unless method_defined?(:perform_without_modified_arguments)
    alias_method :perform, :perform_with_worker_in_arguments
  end 
end

Instance Method Details

#before_perform_ensure_proper_worker(*args) ⇒ Object

Abort gracefully if picked up by the wrong worker (job will be removed from queue)



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# File 'lib/resque/plugins/access_worker_from_job.rb', line 73

def before_perform_ensure_proper_worker(*args)
  if args.last.is_a?(::Resque::Worker)
    self.worker = args.last
  else
    raise "Resque::Job#args has not been overriden to pass worker as last argument."
  end
  
  if required_worker_class && worker.class.name != required_worker_class
    raise ::Resque::Job::DontPerform
  end
end