SecondLevelCache is a write-through and read-through caching library inspired by Cache Money and cache_fu, support ActiveRecord 4.
The available storage adapters for persisting the cache: redis, memcached, dalli, memory
Read-Through: Queries by ID, like current_user.articles.find(params[:id]), will first look in cache store and then look in the database for the results of that query. If there is a cache miss, it will populate the cache.
Write-Through: As objects are created, updated, and deleted, all of the caches are automatically kept up-to-date and coherent.
In your gem file:
gem "second_level_cache", "~> 2.0.0.rc1"For ActiveRecord 3:
gem "second_level_cache", "~> 1.6"For example, cache User objects:
class User < ActiveRecord::Base
acts_as_cached(:version => 1, :expires_in => 1.week)
endThen it will fetch cached object in this situations:
User.find(1)
user.articles.find(1)
User.where(:status => 1).find(1)
article.userCache key:
user = User.find 1
user.second_level_cache_key # We will get the key looks like "slc/user/1/0"Expires cache:
user = User.find(1)
user.expire_second_level_cacheor expires cache using class method:
User.expire_second_level_cache(1)Disable SecondLevelCache:
User.without_second_level_cache do
user = User.find 1
# ...
endOnly SELECT * query will be cached:
# this query will NOT be cached
User.select("id, name").find(1)- SecondLevelCache cache by model name and id, so only find_one query will work.
- Only equal conditions query WILL get cache; and SQL string query like
User.where("name = 'Hooopo'").find(1)WILL NOT work. - SecondLevelCache sync cache after transaction commit:
# user and account's write_second_level_cache operation will invoke after the logger.
ActiveRecord::Base.transaction do
user.save
account.save
Rails.logger.info "info"
end # <- Cache write
# if you want to do something after user and account's write_second_level_cache operation, do this way:
ActiveRecord::Base.transaction do
user.save
account.save
end # <- Cache write
Rails.logger.info "info"- If you are using SecondLevelCache with database_cleaner, you should set cleaning strategy to
:truncation:
DatabaseCleaner.strategy = :truncationAll configuration options are supported globally:
SecondLevelCache.configure do |config|
config.cache_store = CACHE_STORE
config.expires_in = 2.day
config.logger = Padrino.logger
cache_key_prefix = 'slc'
endIn production env, we recommend to use Dalli as cache store.
SecondLevelCache.configure.cache_store = SecondLevelCache::Store::Dalli.new(::Dalli::Client.new('127.0.0.1:11211'))as also you can use memcached:
SecondLevelCache.configure.cache_store = SecondLevelCache::Store::Memcached.new(::Memcached.new('127.0.0.1:11211', :exception_retry_limit => 1))SecondLevelCache.configure.cache_store = SecondLevelCache::Store::Redis.new(::Redis.new(:host => '127.0.0.1', :port => 6379, :db => 0))local memory:
SecondLevelCache.configure.cache_store = SecondLevelCache::Store::Memory.new(50)disable second level cache:
SecondLevelCache.configure.cache_store = false- When you want to clear only second level cache apart from other cache for example fragment cache in cache store,
you can only change the
cache_key_prefix:
SecondLevelCache.configure.cache_key_prefix = "slc1"- When schema of your model changed, just change the
versionof the speical model, avoding clear all the cache.
class User < ActiveRecord::Base
acts_as_cached(:version => 2, :expires_in => 1.week)
end- It provides a great feature, not hits db when fetching record via unique key(not primary key).
# this will fetch from cache
user = User.fetch_by_uniq_key("hooopo", :nick_name)
# this also fetch from cache
user = User.fetch_by_uniq_key!("hooopo", :nick_name) # this will raise `ActiveRecord::RecordNotFound` Exception when nick name not exists.- You can use Rails's Eager Loading feature as normal. Even better, second_level_cache will transform the
INquery into a Rails.cache.multi_read operation. For example:
Answer.includes(:question).limit(10).order("id DESC").each{|answer| answer.question.title}
Answer Load (0.2ms) SELECT `answers`.* FROM `answers` ORDER BY id DESC LIMIT 10 # Only one SQL query and one Rails.cache.read_multi fetching operation.Details for read_multi feature.
MIT License