Blockhole (alpha)

Have an expensive block that you need to cache? Maybe an http response from an expensive third party service?

Inspired heavily from the interface of VCR Blockhole will suck up the response from the block so it only runs once.

Blockhole.use_hole('pie-hole') do
  # some expensive operation that returns some value
end

It currently only supports redis for storage, but more options are forthcoming.

Add this line to your application's Gemfile:

gem 'blockhole'

And then execute:

$ bundle

Or install it yourself as:

$ gem install blockhole

The first step is to configure Blockhole to use your redis connection. Instructions on setting up a redis connection can be found in the redis-rb docs.

Blockhole.configure do |b|
  b.storage = Redis.new(:host => 'localhost', :port => 6379)
end

Next record a block by passing the name of the redis key you would like to use.

my_pie = Blockhole.use_hole('pie-hole') do
  # some expensive operation to get pie
  'cherry pie'
end

puts my_pie
> 'cherry pie'

Blockhole will check redis cache for that key and return that value if it exists (this is called a cache hit). If it doesn't find anything it will run the block, store it's return value in the cache and return it to you.

You can also explicitly get the value back out without passing a block using a get call.

my_pie = Blockhole.get('pie-hole') # still cherry

Anything that can be fed into MultiJson.dump will work. Strings will just be stored and returned as is. Arrays and Hashes will be serialized before storage and then reparsed after retreival.

Blockhole.use_hole('pie-hole') do
  [
    { name: 'cherry' },
    { name: 'peach' }
  ]
end

pies =  Blockhole.get('pie-hole')
puts pies[1][:name]

> 'peach'

You can pass an optional expiration value (in seconds). The key will automatically be deleted after that amount of time has passed.

lifespan = 3600 # 1 hour

my_pie = Blockhole.use_hole('pie-hole', lifespan) do
  # some expensive operation to get pie
end

# an hour passes

my_pie = Blockhole.use_hole('pie-hole', lifespan) do
  # Now it's blueberry!
end

Note that this command will refresh the expiration each time it is called.

If you'd had enough with the existing data you can collapse the hole and clear the cache. This will result in the key being deleted from redis.

Blockhole.collapse('pie-hole')

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request