Class: ASS::RPC

Inherits:
Object
  • Object
show all
Defined in:
lib/ass/rpc.rb

Defined Under Namespace

Classes: Future

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(opts = {}) ⇒ RPC

Returns a new instance of RPC.



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# File 'lib/ass/rpc.rb', line 57

def initialize(opts={})
  raise "can't run rpc client in the same thread as eventmachine" if EM.reactor_thread?
  self.extend(MonitorMixin)
  @seq = 0
  # queue is used be used to synchronize RPC
  # user thread and the AMQP eventmachine thread.
  @buffer = Queue.new
  @ready = {} # the ready results not yet waited
  @futures = {} # all futures not yet waited for.
  # Creates an exclusive queue to serve the RPC client.
  @rpc_id = ASS::RPC.random_id.to_s
  buffer = @buffer # closure binding for reactor
  exchange = ASS.mq.direct("__rpc__")
  @name = "__rpc__#{@rpc_id}"
  queue = ASS.mq.queue(@name,
                       :exclusive => true,
                       :auto_delete => true)
  queue.bind("__rpc__",:routing_key => @rpc_id)
  queue.subscribe { |header,payload|
    payload = ::Marshal.load(payload)
    buffer << [header,payload]
  }
end

Instance Attribute Details

#buffer ⇒ Object (readonly)

Returns the value of attribute buffer.



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# File 'lib/ass/rpc.rb', line 56

def buffer
  @buffer
end

#futures ⇒ Object (readonly)

Returns the value of attribute futures.



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# File 'lib/ass/rpc.rb', line 56

def futures
  @futures
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/ass/rpc.rb', line 55

def name
  @name
end

#ready ⇒ Object (readonly)

Returns the value of attribute ready.



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# File 'lib/ass/rpc.rb', line 56

def ready
  @ready
end

Class Method Details

.random_id ⇒ Object

stolen from nanite



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# File 'lib/ass/rpc.rb', line 9

def self.random_id
    values = [
      rand(0x0010000),
      rand(0x0010000),
      rand(0x0010000),
      rand(0x0010000),
      rand(0x0010000),
      rand(0x1000000),
      rand(0x1000000),
    ]
    "%04x%04x%04x%04x%04x%06x%06x" % values
end

Instance Method Details

#call(server_name, method, data = nil, opts = {}, meta = nil) ⇒ Object 



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# File 'lib/ass/rpc.rb', line 81

def call(server_name,method,data=nil,opts={},meta=nil)
  self.synchronize do
    message_id = @seq.to_s # message gotta be unique for this RPC client.
    # by default route message to the exchange @name@, with routing key @name@
    ASS.call(server_name,
             method,
             data,
             # can't override these options
             opts.merge(:message_id => message_id,
                        :reply_to => "__rpc__",
                        :key => @rpc_id),
             meta)
    @seq += 1
    @futures[message_id] = Future.new(self,message_id)
  end
end

#inspect ⇒ Object 



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# File 'lib/ass/rpc.rb', line 177

def inspect
  "#<#{self.class} #{self.name}>"
end

#wait(future, timeout = nil) ⇒ Object

the idea is to block on a synchronized queue until we get the future we want.

WARNING: blocks forever if the thread calling wait is the same as the EventMachine thread.

It is safe (btw) to use the RPC client within an ASS server/actor, because the wait is in an EM worker thread, rather than the EM thread itself. The EM thread is still free to process the queue. CAVEAT: you could run out of EM worker threads.



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# File 'lib/ass/rpc.rb', line 111

def wait(future,timeout=nil)
  return future.data if future.done? # future was waited before
  # we can have more fine grained synchronization later.
  ## easiest thing to do (later) is use threadsafe hash for @futures and @ready.
  ### But it's actually trickier than
  ### that. Before each @buffer.pop, a thread
  ### has to check again if it sees the result
  ### in @ready.
  self.synchronize do
    timer = nil
    if timeout
      timer = EM.add_timer(timeout) {
        @buffer << [:timeout,future.message_id]
      }
    end
    ready_future = nil
    if @ready.has_key? future.message_id
      @ready.delete future.message_id
      ready_future = future
    else
      while true
        header,payload = @buffer.pop # synchronize. like erlang's mailbox select.
        if header == :timeout # timeout the future we are waiting for.
          message_id = payload
          # if we got a timeout from previous wait. throw it away.
          next if future.message_id != message_id 
          future.timeout = true
          future.done!
          @futures.delete future.message_id
          return yield # return the value of timeout block
        end
        data = payload[:data]
        some_future = @futures[header.message_id]
        # If we didn't find the future among the
        # future, it must have timedout. Just
        # throw result away and keep processing.
        next unless some_future
        some_future.timeout = false
        some_future.header = header
        some_future.data = data
        some_future.method = payload[:method]
        some_future.meta = payload[:meta]
        if some_future == future
          # The future we are waiting for
          EM.cancel_timer(timer) if timer
          ready_future = future
          break
        else
          # Ready, but we are not waiting for it. Save for later.
          @ready[some_future.message_id] = some_future
        end
      end
    end
    ready_future.done!
    @futures.delete ready_future.message_id
    return ready_future.data
  end
  
end

#waitall ⇒ Object 



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# File 'lib/ass/rpc.rb', line 171

def waitall
  @futures.values.map { |k,v|
    wait(v)
  }
end