CacheTree¶ ↑

The idea behind this, is to be able to manage very large ammounts of cache files. and expire millions of cache files in just a few microseconds.

Instead of performing some ActiveRecord#touch and have it creating a massive sequence of queries bouncing off going up/down the herarchies to eliminate a group of items from the cache

CacheTree stores cache in trees, actually it borrows the btree strategy to fetch and quickly determine where cache files are.

you can always add new subtrees or create new trees and handle the cache at different levels. no matter where you are cache expiring is superfast.

While the actual deletion of the expired cache files is also fast. it is recomended to do so in some sort of background job solution.

Trees are cool :)

require 'rubygems'
require 'cache_tree'

# Setup
CacheTree::Node.directory = 'cache/tree'

# Create a cache node in the tree
node = CacheTree.node({:name => 'node', :value => 1})

# Store data into cache!
puts CacheTree.use(node) { 'This is my complex operation!' }

# Pull data from the cache, if exists in cache and all that is
# handled internally!
puts CacheTree.use(node) { 'Even if this changes cached data will be returned' }

# Expiring!
node.expire

# Removing expired files!
node.clean

require 'rubygems'
require 'cache_tree'

# Setup
CacheTree::Node.directory = 'cache/tree'

# Create/Handle two separated cache trees.
parent_1 = CacheTree.node({:name => 'parent_1', :value => 1})
parent_2 = CacheTree.node({:name => 'parent_2', :value => 2})

# Each tree has sub-nodes.
child_1 = CacheTree.node({:name => 'child_1', :value => 1})
child_2 = CacheTree.node({:name => 'child_2', :value => 2})
child_3 = CacheTree.node({:name => 'child_3', :value => 3})

# Create a cache tree relationship between the nodes.
parent_1.add_child(child_1)
parent_2.add_child(child_2)
parent_1.add_child(child_3)

puts CacheTree.use(child_1) { 'This is child 1 cache' }
puts CacheTree.use(child_2) { 'This is child 2 cache' }
puts CacheTree.use(child_3) { 'This is child 3 cache' }

# Expire cache for all nodes below parent 1.
parent_1.expire

# parent 2 cache is still active at this point, parent 1 cache needs to be regenerated.

# remove expired files from child nodes (1, 3)
child_1.clean
child_3.clean

bash-3.2$ ruby cache_tree.usage_example.rb
This is child 1 cache
This is child 2 cache
This is child 3 cache
bash-3.2$ tree cache
cache
`-- tree
    |-- parent_1
    |   `-- 1
    |       |-- btree.key
    |       |-- child_1
    |       |   `-- 1
    |       |       `-- btree.key
    |       `-- child_3
    |           `-- 3
    |               `-- btree.key
    `-- parent_2
        `-- 2
            |-- btree.key
            `-- child_2
                `-- 2
                    |-- btree.key
                    `-- c1533963ef2c86a1f8c80cde871d0b09.cache

11 directories, 6 files
bash-3.2$ cat cache/tree/parent_2/2/child_2/2/c1533963ef2c86a1f8c80cde871d0b09.cache
This is child 2 cache

require 'rubygems'
require 'cache_tree'

# Mocks
class ActiveRecordMock
  attr_accessor :id
  def initialize
    @id = 1
  end
end

class User    < ActiveRecordMock; end
class Post    < ActiveRecordMock; end
class Comment < ActiveRecordMock; end
class Like    < ActiveRecordMock; end

# Easily Setup complex cached trees.
user    = CacheTree.node(User.new)
post    = CacheTree.node(Post.new)
comment = CacheTree.node(Comment.new)
like    = CacheTree.node(Like.new)

user.add_child(post)
post.add_child(comment)
comment.add_child(like)

# Setup
CacheTree::Node.directory = 'cache/tree'

# Example Usage.
# - first time block gets executed
# - second time will be pulled out from cache!
# - you can grab any of the nodes and expire all the cache below that
#   node
puts CacheTree.use(like) { 'Generating cache' }

# Expire all cache below post with id 1 but leave user cache alone.
post.expire

puts CacheTree.use(like) { 'Generating new cache' }
puts CacheTree.use(like) { 'xxxxxxxxxxxxxxxxxxxx' } # => will output 'Generating new cache'

# you can debug any node to figure out what is going on with the cache
# at that particular point.
# - when debugging, the actual cache file will be shown in green
#   (active cache)
# - all dead cache will be shown in red
# - if cache file has not been generated it would be printed in yellow!
like.debug

# Use this to remove expired cache files.
like.clean

Copyright © 2012 kazuyoshi tlacaelel. See LICENSE.txt for further details.