Move queue classes to ActiveSupport

1 files changed, 116 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/queueing.rb b/activesupport/lib/active_support/queueing.rb
new file mode 100644
index 0000000000..f397e1c0c5
--- /dev/null
+++ b/activesupport/lib/active_support/queueing.rb
@@ -0,0 +1,116 @@
+require 'delegate'
+require 'thread'
+
+module ActiveSupport
+  # A Queue that simply inherits from STDLIB's Queue. Everytime this
+  # queue is used, Rails automatically sets up a ThreadedConsumer
+  # to consume it.
+  class Queue < ::Queue
+  end
+
+  class SynchronousQueue < ::Queue
+    def push(job)
+      result = nil
+      Thread.new { result = job.run }.join
+      result
+    end
+    alias <<  push
+    alias enq push
+  end
+
+  # In test mode, the Rails queue is backed by an Array so that assertions
+  # can be made about its contents. The test queue provides a +jobs+
+  # method to make assertions about the queue's contents and a +drain+
+  # method to drain the queue and run the jobs.
+  #
+  # Jobs are run in a separate thread to catch mistakes where code
+  # assumes that the job is run in the same thread.
+  class TestQueue < ::Queue
+    # Get a list of the jobs off this queue. This method may not be
+    # available on production queues.
+    def jobs
+      @que.dup
+    end
+
+    # Marshal and unmarshal job before pushing it onto the queue.  This will
+    # raise an exception on any attempts in tests to push jobs that can't (or
+    # shouldn't) be marshalled.
+    def push(job)
+      super Marshal.load(Marshal.dump(job))
+    end
+
+    # Drain the queue, running all jobs in a different thread. This method
+    # may not be available on production queues.
+    def drain
+      # run the jobs in a separate thread so assumptions of synchronous
+      # jobs are caught in test mode.
+      Thread.new { pop.run until empty? }.join
+    end
+  end
+
+  # A container for multiple queues. This class delegates to a default Queue
+  # so that <tt>Rails.queue.push</tt> and friends will Just Work. To use this class
+  # with multiple queues:
+  #
+  #   # In your configuration:
+  #   Rails.queue[:image_queue] = SomeQueue.new
+  #   Rails.queue[:mail_queue]  = SomeQueue.new
+  #
+  #   # In your app code:
+  #   Rails.queue[:mail_queue].push SomeJob.new
+  #
+  class QueueContainer < DelegateClass(::Queue)
+    def initialize(default_queue)
+      @queues = { :default => default_queue }
+      super(default_queue)
+    end
+
+    def [](queue_name)
+      @queues[queue_name]
+    end
+
+    def []=(queue_name, queue)
+      @queues[queue_name] = queue
+    end
+  end
+
+  # The threaded consumer will run jobs in a background thread in
+  # development mode or in a VM where running jobs on a thread in
+  # production mode makes sense.
+  #
+  # When the process exits, the consumer pushes a nil onto the
+  # queue and joins the thread, which will ensure that all jobs
+  # are executed before the process finally dies.
+  class ThreadedQueueConsumer
+    def self.start(queue, logger=nil)
+      new(queue, logger).start
+    end
+
+    def initialize(queue, logger=nil)
+      @queue  = queue
+      @logger = logger
+    end
+
+    def start
+      @thread = Thread.new do
+        while job = @queue.pop
+          begin
+            job.run
+          rescue Exception => e
+            handle_exception e
+          end
+        end
+      end
+      self
+    end
+
+    def shutdown
+      @queue.push nil
+      @thread.join
+    end
+
+    def handle_exception(e)
+      @logger.error "Job Error: #{e.message}\n#{e.backtrace.join("\n")}" if @logger
+    end
+  end
+end