module MultiCache

Constants

CACHE_KEY_MASTER_PREFIX

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After installation:

Create config/initializers/init_multi_cache.rb
and add the line
    Rails.application.config.multi_cache_redis = "<redis-instance>"
  where <redis-instance> is the Redis::Namespace object to be used by 
  MultiCache for caching
  Please ensure that the redis-instance is specified in quotes

All models where you want to use MultiCache must:

[mandatory]   Define a CLASS method
              MULTI_CACHE_PREFIXES
                that returns an array of allowed cache prefixes used by
                the class   

[mandatory]   Define a CLASS method 
              GEN_CACHE_CONTENT(ID_OR_OBJ, CACHE_PREFIX)
                that generates a hash that will be cached
                ID_OR_OBJ is a hash that contains 
                  {:id => obj_id, :obj => actual_obj_if_available}
              CACHE_PREFIX is an optional string that can be used to 
                distinguish between different cached info for the same
                object.

[optional]    Define a CLASS method 
              PARSE_CACHE_CONTENT(CONTENT, CACHE_PREFIX)
                that parses the cached content once it is read from 
                redis. Sometimes some JSON.parses are required. If not
                defined, the default method is called (which simply returns
                the cached value as-is)

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CACHE_KEY_SEPARATOR

MULTICACHE_REDIS

VERSION

Public Class Methods

del_from_redis(prefix_match) click to toggle source

# File lib/MultiCache.rb, line 143
def self.del_from_redis(prefix_match) 
  Thread.new do
    MULTICACHE_REDIS.keys("#{prefix_match}*").each do |prefix|
      MULTICACHE_REDIS.del(prefix)
      # TODO: Use scan instead of keys
    end
  end
end

destroy_cache_keys() click to toggle source

# File lib/MultiCache.rb, line 110
def self.destroy_cache_keys
  # Destroy cache for all MultiCache
  MultiCache.del_from_redis(CACHE_KEY_MASTER_PREFIX)
end

destroy_class_cache() click to toggle source

# File lib/MultiCache.rb, line 104
def self.destroy_class_cache
  # Destroy cache for all objects of this class
  prefix = self.fixed_cache_prefix
  MultiCache.del_from_redis(prefix)
end

destroy_obj_cache(id) click to toggle source

# File lib/MultiCache.rb, line 98
def self.destroy_obj_cache(id)
  # Delete cache for one object only
  prefix = self.fixed_cache_prefix(id)
  MultiCache.del_from_redis(prefix)
end

fixed_cache_prefix(id = nil) click to toggle source

# File lib/MultiCache.rb, line 85
def self.fixed_cache_prefix(id = nil)
  chain = [CACHE_KEY_MASTER_PREFIX, self.name.to_s]
  chain.push(id.to_s.strip) if id.present?
  chain.join(CACHE_KEY_SEPARATOR)
end

get_cached(id_or_obj, cache_prefix) click to toggle source

# File lib/MultiCache.rb, line 52
def self.get_cached(id_or_obj, cache_prefix)
  id_and_obj = get_id_and_obj(id_or_obj)

  validate_cache_prefix(cache_prefix)

  cache_key = obj_cache_key(id_and_obj[:id], cache_prefix)
  cached = MULTICACHE_REDIS.hgetall(cache_key)

  if cached.blank?
    cached = gen_cache_content(id_or_obj, cache_prefix)

    raise "the output of GEN_CACHE_CONTENT must be a hash" if !(cached.is_a?Hash)
    if cached.present?
      MULTICACHE_REDIS.hmset(cache_key, *(cached.to_a.reduce([], :+)))
    end
    cached = MULTICACHE_REDIS.hgetall(cache_key)
  end

  parse_cache_content(cached, cache_prefix)
end

get_id_and_obj(id_or_obj) click to toggle source

# File lib/MultiCache.rb, line 123
def self.get_id_and_obj(id_or_obj)
  id_and_obj = {}
  if id_or_obj.class == self
    id_and_obj[:obj] = id_or_obj
    id_and_obj[:id] = obj.id.to_s
  else
    id_and_obj[:id] = id_or_obj.to_s
    # obj = nil # Load it when necessary
  end
  id_and_obj
end

obj_cache_key(id, custom_prefix) click to toggle source

# File lib/MultiCache.rb, line 80
def self.obj_cache_key(id, custom_prefix)
  # Do not change ordering since we match keys using this
  [fixed_cache_prefix(id), custom_prefix.to_s].join(CACHE_KEY_SEPARATOR)
end

parse_cache_content(content, cache_prefix) click to toggle source

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# File lib/MultiCache.rb, line 118
def self.parse_cache_content(content, cache_prefix)
  # Default method. Override in including class.
  content
end

validate_cache_prefix(cache_prefix) click to toggle source

# File lib/MultiCache.rb, line 135
def self.validate_cache_prefix(cache_prefix)
  if !(multi_cache_prefixes.include?cache_prefix)
    raise "#{self} Class: cache prefix '#{cache_prefix}' " + 
          "must be among #{multi_cache_prefixes}"
  end
end

Public Instance Methods

destroy_obj_cache(cb_obj = nil) click to toggle source

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# File lib/MultiCache.rb, line 94
def destroy_obj_cache(cb_obj = nil)
  self.class.destroy_obj_cache(self.id)
end

obj_cache_key(cache_prefix) click to toggle source

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# File lib/MultiCache.rb, line 76
def obj_cache_key(cache_prefix)
  self.class.obj_cache_key(self.id, cache_prefix)
end