Class: Card::Cache::Persistent

Inherits:
Object
  • Object
show all
Extended by:
PersistentClass
Defined in:
card/lib/card/cache/persistent.rb

Overview

Persistent (or Hard) caches closely mirror the database and are intended to be altered only upon database alterations.

Unlike the database, the persistent cache stores records of records that have been requested but are missing or, in the case of some cards, “virtual”, meaning that they follow known patterns but do not exist in the database.

Most persistent cache implementations cannot store objects with singleton classes, therefore cards generally must have set_modules re-included after retrieval from the persistent cache.

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from PersistentClass

new_stamp

Constructor Details

#initialize(opts) ⇒ Persistent

Returns a new instance of Persistent.

Parameters:

  • opts (Hash)

Options Hash (opts):

  • :store (Rails::Cache)
  • :class, (ruby Class)

    typically ActiveRecord descendant

  • :database (String)


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# File 'card/lib/card/cache/persistent.rb', line 26

def initialize opts
  @store = opts[:store]
  @klass = opts[:class]
  @class_key = @klass.to_s.to_name.key
  @database = opts[:database] || Cardio.database_name
end

Instance Attribute Details

#prefixObject

prefix added to cache key to create a system-wide unique key



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# File 'card/lib/card/cache/persistent.rb', line 67

def prefix
  @prefix
end

Instance Method Details

#annihilateObject

the nuclear option. can affect other applications sharing the same cache engine. keep in mind mutually assured destruction.



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# File 'card/lib/card/cache/persistent.rb', line 50

def annihilate
  @store.clear
end

#deep_read(key) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 95

def deep_read key
  local_cache = @store.send :local_cache
  local_cache&.clear
  read key
end

#delete(key) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 114

def delete key
  @store.delete full_key(key)
end

#exist?(key) ⇒ Boolean

Returns:

  • (Boolean)


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# File 'card/lib/card/cache/persistent.rb', line 118

def exist? key
  @store.exist? full_key(key)
end

#fetch(key, &block) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 110

def fetch key, &block
  @store.fetch full_key(key), &block
end

#full_key(key) ⇒ String

returns prefix/key

Parameters:

  • key (String)

Returns:

  • (String)


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# File 'card/lib/card/cache/persistent.rb', line 74

def full_key key
  "#{prefix}/#{key}"
end

#read(key) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 78

def read key
  @store.read full_key(key)
end

#read_attribute(key, attribute) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 101

def read_attribute key, attribute
  object = deep_read key
  object.instance_variable_get "@#{attribute}"
end

#renewObject

renew insures you’re using the most current cache version by reaffirming the stamp and prefix



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# File 'card/lib/card/cache/persistent.rb', line 35

def renew
  @stamp = nil
  @prefix = nil
end

#resetObject

reset effectively clears the cache by setting a new stamp. However unlike annihilate, it won’t bother other apps using the same cache engine.



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# File 'card/lib/card/cache/persistent.rb', line 42

def reset
  @stamp = self.class.new_stamp
  @prefix = nil
  Cardio.cache.write stamp_key, @stamp
end

#stampObject

the current time stamp. changing this value effectively resets the cache. Note that Cardio.cache is a simple Rails::Cache, not a Card::Cache object.



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# File 'card/lib/card/cache/persistent.rb', line 57

def stamp
  @stamp ||= Cardio.cache.fetch(stamp_key) { self.class.new_stamp }
end

#stamp_keyObject

key for looking up the current stamp



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# File 'card/lib/card/cache/persistent.rb', line 62

def stamp_key
  "#{@database}-#{@class_key}-#{self.class.stamp}-stamp"
end

#write(key, value) ⇒ Object



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# File 'card/lib/card/cache/persistent.rb', line 106

def write key, value
  @store.write full_key(key), value
end

#write_attribute(key, attribute, value) ⇒ Object

update an attribute of an object already in the cache

Parameters:

  • key (String)
  • attribute (String, Symbol)


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# File 'card/lib/card/cache/persistent.rb', line 85

def write_attribute key, attribute, value
  return value unless @store

  if (object = deep_read key)
    object.instance_variable_set "@#{attribute}", value
    write key, object
  end
  value
end