Skip to content
master
Go to file
Code

Latest commit

 

Git stats

Files

Permalink
Failed to load latest commit information.
Type
Name
Latest commit message
Commit time
 
 
lib
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

README.md

SecondLevelCache

Gem Version Build Status Code Climate

SecondLevelCache is a write-through and read-through caching library inspired by Cache Money and cache_fu, support ActiveRecord 4, ActiveRecord 5 and ActiveRecord 6.

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.

Install

In your gem file:

ActiveRecord 5.2 and 6.0:

gem 'second_level_cache', '~> 2.6.3'

ActiveRecord 5.0.x, 5.1.x:

gem 'second_level_cache', '~> 2.3.0'

For ActiveRecord 4:

gem "second_level_cache", "~> 2.1.9"

For ActiveRecord 3:

gem "second_level_cache", "~> 1.6"

Usage

For example, cache User objects:

class User < ActiveRecord::Base
  second_level_cache expires_in: 1.week
end

Then it will fetch cached object in this situations:

User.find(1)
user.articles.find(1)
User.where(status: 1).find(1)
User.where(id: 1).first # or .last
article.user

Cache 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_cache

or expires cache using class method:

User.expire_second_level_cache(1)

Disable SecondLevelCache:

User.without_second_level_cache do
  user = User.find(1)
  # ...
end

Only SELECT * query will be cached:

# this query will NOT be cached
User.select("id, name").find(1)

Notice

  • 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 = :truncation

Configure

In production env, we recommend to use Dalli as Rails cache store.

config.cache_store = [:dalli_store, APP_CONFIG["memcached_host"], { namespace: "ns", compress: true }]

Tips:

  • 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 (default: slc):
SecondLevelCache.configure.cache_key_prefix = "slc1"
  • SecondLevelCache was added model schema digest as cache version, this means when you add/remove/change columns, the caches of this Model will expires.
  • When your want change the model cache version by manualy, just add the version option like this:
class User < ActiveRecord::Base
  second_level_cache 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_keys(nick_name: "hooopo")
post = Post.fetch_by_uniq_keys(user_id: 2, slug: "foo")

# this also fetch from cache
user = User.fetch_by_uniq_keys!(nick_name: "hooopo") # 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 IN query 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.

Original design by:

Contributors

Contributor List

License

MIT License

About

Write Through and Read Through caching library inspired by CacheMoney and cache_fu, support ActiveRecord 4 and 5.

Topics

Resources

Languages

You can’t perform that action at this time.