Add bin and edit workflow

bin/gems/eventmachine-1.2.7/lib/em/pool.rb

@@ -0,0 +1,151 @@
+module EventMachine
+  # A simple async resource pool based on a resource and work queue. Resources
+  # are enqueued and work waits for resources to become available.
+  #
+  # @example
+  #   require 'em-http-request'
+  #
+  #   EM.run do
+  #     pool  = EM::Pool.new
+  #     spawn = lambda { pool.add EM::HttpRequest.new('http://example.org') }
+  #     10.times { spawn[] }
+  #     done, scheduled = 0, 0
+  #
+  #     check = lambda do
+  #       done += 1
+  #       if done >= scheduled
+  #         EM.stop
+  #       end
+  #     end
+  #
+  #     pool.on_error { |conn| spawn[] }
+  #
+  #     100.times do |i|
+  #       scheduled += 1
+  #       pool.perform do |conn|
+  #         req = conn.get :path => '/', :keepalive => true
+  #
+  #         req.callback do
+  #           p [:success, conn.object_id, i, req.response.size]
+  #           check[]
+  #         end
+  #
+  #         req.errback { check[] }
+  #
+  #         req
+  #       end
+  #     end
+  #   end
+  #
+  # Resources are expected to be controlled by an object responding to a
+  # deferrable/completion style API with callback and errback blocks.
+  #
+  class Pool
+
+    def initialize
+      @resources = EM::Queue.new
+      @removed = []
+      @contents = []
+      @on_error = nil
+    end
+
+    def add resource
+      @contents << resource
+      requeue resource
+    end
+
+    def remove resource
+      @contents.delete resource
+      @removed << resource
+    end
+
+    # Returns a list for introspection purposes only. You should *NEVER* call
+    # modification or work oriented methods on objects in this list. A good
+    # example use case is periodic statistics collection against a set of
+    # connection resources.
+    #
+    # @example
+    #   pool.contents.inject(0) { |sum, connection| connection.num_bytes }
+    def contents
+      @contents.dup
+    end
+
+    # Define a default catch-all for when the deferrables returned by work
+    # blocks enter a failed state. By default all that happens is that the
+    # resource is returned to the pool. If on_error is defined, this block is
+    # responsible for re-adding the resource to the pool if it is still usable.
+    # In other words, it is generally assumed that on_error blocks explicitly
+    # handle the rest of the lifetime of the resource.
+    def on_error *a, &b
+      @on_error = EM::Callback(*a, &b)
+    end
+
+    # Perform a given #call-able object or block. The callable object will be
+    # called with a resource from the pool as soon as one is available, and is
+    # expected to return a deferrable.
+    # 
+    # The deferrable will have callback and errback added such that when the
+    # deferrable enters a finished state, the object is returned to the pool.
+    #
+    # If on_error is defined, then objects are not automatically returned to the
+    # pool.
+    def perform(*a, &b)
+      work = EM::Callback(*a, &b)
+
+      @resources.pop do |resource|
+        if removed? resource
+          @removed.delete resource
+          reschedule work
+        else
+          process work, resource
+        end
+      end
+    end
+    alias reschedule perform
+
+    # A peek at the number of enqueued jobs waiting for resources
+    def num_waiting
+      @resources.num_waiting
+    end
+
+    # Removed will show resources in a partial pruned state. Resources in the
+    # removed list may not appear in the contents list if they are currently in
+    # use.
+    def removed? resource
+      @removed.include? resource
+    end
+
+    protected
+    def requeue resource
+      @resources.push resource
+    end
+
+    def failure resource
+      if @on_error
+        @contents.delete resource
+        @on_error.call resource
+        # Prevent users from calling a leak.
+        @removed.delete resource
+      else
+        requeue resource
+      end
+    end
+
+    def completion deferrable, resource
+      deferrable.callback { requeue resource }
+      deferrable.errback  { failure resource }
+    end
+
+    def process work, resource
+      deferrable = work.call resource
+      if deferrable.kind_of?(EM::Deferrable)
+        completion deferrable, resource
+      else
+        raise ArgumentError, "deferrable expected from work"
+      end
+    rescue
+      failure resource
+      raise
+    end
+  end
+end