Lightly - Ruby File Cache

Lightly is a file cache for performing heavy tasks, lightly.

$ gem install lightly

Or with bundler:

gem 'lightly'

Lightly can be used both as an instance, and as a static class.

require 'lightly'

# Instance
lightly = Lightly.new life: '3h'
response = lightly.get 'key' do
  # Heavy operation here
end

# Static
Lightly.life = '3h'
response = Lightly.get 'key' do
  # Heavy operation here
end

The design intention is to provide both a globally available singleton Lightly object, as well as multiple caching instances, with different settings - depending on the use case.

Note that the examples in this document are all using the instance syntax, but all methods are also available statically.

This is the basic usage pattern:

require 'lightly'

lightly = Lightly.new

content = lightly.get 'key' do
  # Heavy operation here
  entire_internet.download
end

This will look for a cached object with the given key and return it if it exists and not older than 1 hour. Otherwise, it will perform the operation inside the block, and save it to the cache object.

By default, the cached objects are stored in the ./cache directory, and expire after 60 minutes. The cache directory will be created as needed.

In addition, the provided key is hashed to its MD5 representation, and the file permissions are optionally set.

You can change these settings on initialization:

lightly = Lightly.new dir: 'tmp/my_cache', life: 7200,
  hash: false, permissions: 0o640

Or later:

lightly = Lightly.new
lightly.dir = 'tmp/my_cache'
lightly.life = '1d'
lightly.hash = false
lightly.permissions = 0o640

The life property accepts any of these formats:

lightly.life = 10     # 10 seconds
lightly.life = '20s'  # 20 seconds
lightly.life = '10m'  # 10 minutes
lightly.life = '10h'  # 10 hours
lightly.life = '10d'  # 10 days

To check if a key is cached, use the cached? method:

lightly = Lightly.new
lightly.cached? 'example'
# => false

content = lightly.get 'example' do
  open('http://example.com').read
end

lightly.cached? 'example'
# => true

You can enable/disable the cache at any time:

lightly = Lightly.new
lightly.disable
lightly.enabled? 
# => false

content = lightly.get 'example' do
  open('http://example.com').read
end

lightly.cached? 'example'
# => false

lightly.enable

content = lightly.get 'example' do
  open('http://example.com').read
end

lightly.cached? 'example'
# => true

To flush the cache, call:

lightly = Lightly.new
lightly.flush

To clear the cache for a given key, call:

lightly = Lightly.new
lightly.clear 'example'

To clear all expired keys, call:

lightly = Lightly.new
lightly.prune

If your block returns false or nil, the data will not be cached:

result = lightly.get 'test' do
  false
end

puts lightly.cached? 'test'
# => false

For a similar gem that provides caching specifically for HTTP downloads, see the WebCache gem.

If you experience any issue, have a question or a suggestion, or if you wish to contribute, feel free to open an issue.