Class: StarlingServer::QueueCollection

Inherits:
Object
  • Object
show all
Defined in:
lib/starling/queue_collection.rb

Overview

QueueCollection is a proxy to a collection of PersistentQueue instances.

Instance Method Summary collapse

Constructor Details

#initialize(path) ⇒ QueueCollection

Create a new QueueCollection at path



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# File 'lib/starling/queue_collection.rb', line 16

def initialize(path)
  unless File.directory?(path) && File.writable?(path)
    raise InaccessibleQueuePath.new("'#{path}' must exist and be read-writable by #{Etc.getpwuid(Process.uid).name}.")
  end

  @shutdown_mutex = Mutex.new

  @path = path
  @logger = StarlingServer::Base.logger

  @queues = {}
  @queue_init_mutexes = {}

  @stats = Hash.new(0)
end

Instance Method Details

#close ⇒ Object

Safely close all queues.



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# File 'lib/starling/queue_collection.rb', line 133

def close
  @shutdown_mutex.lock
  @queues.each_pair do |name,queue|
    queue.close
    @queues.delete(name)
  end
end

#delete(key) ⇒ Object 



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# File 'lib/starling/queue_collection.rb', line 63

def delete(key)
  queue = @queues.delete(key)
  return if queue.nil?
  queue.purge
end

#put(key, data) ⇒ Object

Puts data onto the queue named key



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# File 'lib/starling/queue_collection.rb', line 35

def put(key, data)
  queue = queues(key)
  return nil unless queue

  @stats[:current_bytes] += data.size
  @stats[:total_items] += 1

  queue.push(data)

  return true
end

#queues(key = nil) ⇒ Object

Returns all active queues.



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# File 'lib/starling/queue_collection.rb', line 72

def queues(key=nil)
  return nil if @shutdown_mutex.locked?

  return @queues if key.nil?

  # First try to return the queue named 'key' if it's available.
  return @queues[key] if @queues[key]

  # If the queue wasn't available, create or get the mutex that will
  # wrap creation of the Queue.
  @queue_init_mutexes[key] ||= Mutex.new

  # Otherwise, check to see if another process is already loading
  # the queue named 'key'.
  if @queue_init_mutexes[key].locked?
    # return an empty/false result if we're waiting for the queue
    # to be loaded and we're not the first process to request the queue
    return nil
  else
    begin
      @queue_init_mutexes[key].lock
      # we've locked the mutex, but only go ahead if the queue hasn't
      # been loaded. There's a race condition otherwise, and we could
      # end up loading the queue multiple times.
      if @queues[key].nil?
        @queues[key] = PersistentQueue.new(@path, key)
        @stats[:current_bytes] += @queues[key].initial_bytes
      end
    rescue Object => exc
      puts "ZOMG There was an exception reading back the queue. That totally sucks."
      puts "The exception was: #{exc}. Backtrace: #{exc.backtrace.join("\n")}"
    ensure
      @queue_init_mutexes[key].unlock
    end
  end

  return @queues[key]
end

#stats(stat_name) ⇒ Object

Returns statistic stat_name for the QueueCollection.

Valid statistics are:

[:get_misses]    Total number of get requests with empty responses
[:get_hits]      Total number of get requests that returned data
[:current_bytes] Current size in bytes of items in the queues
[:current_size]  Current number of items across all queues
[:total_items]   Total number of items stored in queues.



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# File 'lib/starling/queue_collection.rb', line 122

def stats(stat_name)
  case stat_name
  when nil; @stats
  when :current_size; current_size
  else; @stats[stat_name]
  end
end

#take(key) ⇒ Object

Retrieves data from the queue named key



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# File 'lib/starling/queue_collection.rb', line 50

def take(key)
  queue = queues(key)
  if queue.nil? || queue.length == 0
    @stats[:get_misses] += 1
    return nil
  else
    @stats[:get_hits] += 1
  end
  result = queue.pop
  @stats[:current_bytes] -= result.size
  result
end