Class: Arrow::Cache

Inherits:

Cache

• Object
• Cache
• Arrow::Cache

show all

Extends:

Forwardable

Includes:

Loggable

Defined in:

lib/arrow/cache.rb

Overview

Constant Summary

DefaultConfig =

Default configuration values

{
  :maxNum     => 10,
  :maxObjSize   => nil,
  :maxSize    => nil,
  :expiration   => 3600,
}

Class Attribute Summary

• + (Object) extent readonly

  Returns the value of attribute extent.

Instance Attribute Summary

• - (Object) hits readonly

  Total count of cache hits.

• - (Object) list readonly

  The list of cached objects.

• - (Object) misses readonly

  Total count of cache misses.

• - (Object) name readonly

  The name of the cache; used in introspection.

• - (Object) size readonly

  Cache size in bytes.

Instance Method Summary

• - (Object) []=(key, obj)

  Overridden from the superclass to prevent .to_s from being called on objects to determine their size if the object supports a #memsize method.

• - (Object) expire

  Overridden to provide logging of expire phase.

• - (Cache) initialize(name, config = {}, &cleanup) constructor

  Create a new cache.

• - (Object) invalidate(key)

  Overridden to provide logging of invalidated keys.

• - (Object) invalidate_all

  Overridden for logging.

Methods included from Loggable

#log

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# File 'lib/arrow/cache.rb', line 53

def initialize( name, config={}, &cleanup )
  @name = name

  # Merge defaults and specified values
  merged = DefaultConfig.merge( config )

  # Transform the config hash into the form the superclass expects
  merged.each_key do |key|
    lckey = key.to_s.gsub( /(.)([A-Z])/ ) {|match|
      match[0,1] + "_" + match[1,1].downcase
    }.to_sym

    next if key == lckey
    merged[ lckey ] = merged.delete( key )
  end

  # Register this instance with the class for introspection (costs
  # much less than ObjectSpace.each_object).
  obj = super( merged, &cleanup )
  self.class.extent << obj

  return obj
end

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# File 'lib/arrow/cache.rb', line 43

def extent
  @extent
end

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# File 'lib/arrow/cache.rb', line 90

def hits
  @hits
end

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# File 'lib/arrow/cache.rb', line 99

def list
  @list
end

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# File 'lib/arrow/cache.rb', line 93

def misses
  @misses
end

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# File 'lib/arrow/cache.rb', line 87

def name
  @name
end

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# File 'lib/arrow/cache.rb', line 96

def size
  @size
end

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# File 'lib/arrow/cache.rb', line 127

def []=( key, obj )
  self.expire
  
  self.invalidate( key ) if self.cached?( key )

  if obj.respond_to?( :memsize )
    size = obj.memsize
  else
    size = obj.to_s.size
  end

  # Test against size threshold
  if @max_obj_size && size > @max_obj_size
    Arrow::Logger[self.class].debug \
      "%p not cached: size exceeds maxObjSize: %d" %
      [ obj, @max_obj_size ]
    return obj
  end
  if @max_obj_size.nil? && @max_size && size > @max_size
    Arrow::Logger[self.class].debug \
      "%p not cached: size exceeds maxSize: %d" %
      [ obj, @max_size ]
    return obj
  end
  
  if @max_num && @list.size >= @max_num
    Arrow::Logger[self.class].debug \
      "Dropping %p from the cache: count exceeds maxNum: %d" %
      [ @list.first, @max_num ]
    self.invalidate( @list.first )
  end

  @size += size
  if @max_size
    while @size > @max_size
      Arrow::Logger[self.class].debug \
        "Dropping %p from the cache: size exceeds maxSize: %d" %
        [ @list.first, @max_size ]
      self.invalidate( @list.first )
    end
  end

  @objs[ key ] = Cache::CACHE_OBJECT.new( obj, size, Time.now.to_i )
  @list.push( key )

  return obj
end

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# File 'lib/arrow/cache.rb', line 117

def expire
  self.log.debug "looking for expired entries in %s" % [self.name]
  super
end

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# File 'lib/arrow/cache.rb', line 103

def invalidate( key )
  self.log.debug "invalidating cache key '%p' for %s" % [key, self.name]
  super
end

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# File 'lib/arrow/cache.rb', line 110

def invalidate_all
  self.log.debug "invalidating all cached objects for %s" % [self.name]
  super
end