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README.md

Stockpile Build Status Code Climate Gem Version

Stockpile is a simple cache written in Ruby backed by Redis. It has built in cache-stampede (also known as dog-piling) protection.

Can be used with any Ruby or Ruby on Rails project. Can be used as a replacement for existing Ruby on Rails cache.

Intended as a heavy usage cache to prevent concurrent execution of code when cache is expired that will lead to congestion collapse of your systems.

Upon caching serializes cached value using Oj gem. While reading value from cache will deserialize value from cache using same gem.

How it works

When perform_cached method is invoked with a key and a block of code as arguments Stockpile will attempt to fetch value from cache using given key. If no value is returned it will set a lock deferring all other requests for given key (for specified amount of time) and run provided block of code and storing it's return value at the key. After that a lock will be released allowing other requests to fetch their values from cache.

In case there is a cache miss and an active execution lock for a given key is present request will go into slumber for 2 seconds (configurable by STOCKPILE_SLUMBER environment variable or by calling slumber method on configuration object). During slumber request will keep trying to read value from cache and if no result is returned during that time cache will be bypassed and value will be computed by executing passed in block.

Installation

Add the following line to your Gemfile:

gem 'stockpile_cache'

And run bundle from your shell.

To install gem manually run from your shell:

gem install stockpile_cache

Requirements

Only requirement to run this gem is Redis. Other than that it is not dependant on any other framework or system.

Configration

The only thing you need to set up is URL of your Redis server. You can do this by either setting STOCKPILE_REDIS_URL environment variable or by executing following code during runtime. For Ruby on Rails create config/initializers/stockpile.rb file and put the following code in there:

Stockpile.configure do |configuration|
  configuration.redis_url = <REDIS_URL>
end

There are two ways to configure Stockpile: using environment variables or invoking configuration block during runtime.

Following settings are supported:

Variable Method Settings
STOCKPILE_CONNECTION_POOL connection_pool Redis connection pool size to share amongst the fibers or threads in your Ruby. Defaults to 100.
STOCKPILE_CONNECTION_TIMEOUT connection_timeout How long to wait for a connection from connection pool to become available (in seconds). Defaults to 3.
STOCKPILE_LOCK_EXPIRATION lock_expiration Time to keep execution lock alive (in seonds). Defaults to 10.
STOCKPILE_REDIS_URL redis_url URL of your Redis server that will be used for caching. Defaults to redis://localhost:6379/1.
STOCKPILE_REDIS_SENTINELS sentinels (optional) Comma separated list of Sentinels IPs for Redis. Defaults to nil. Example value: 8.8.8.8:42,8.8.4.4:42.
STOCKPILE_SLUMBER slumber Timeout (in seconds) for stampede protection lock. After timeout passed in code will be executed instead of reading a value from cache. Defaults to 2.

Usage

To use simply wrap your code into perform_cached block:

Stockpile.perform_cached(key: 'meaning_of_life', ttl: 42) do
  21 + 21
end

perform method accepts 3 named arguments:

Argument Meaning
key Pointer in cache by which a value will be either looked up or stored in cache once code provided in block is executed.
ttl (optional) Time in seconds for which a cached value will be stored. Defaults to 300 seconds (5 minutes).
&block Block of code to execute; it's return value will be stored in cache.

Caveats

There is no timeout or rescue set for code you will be running through the cache. If you need to do either you have to handle it outside of Stockpile.

Locks are never set indefinitely and by default will expire after 10 seconds allowing next request to trigger cache recalculation. Lock duration is configurable by either setting STOCKPILE_LOCK_EXPIRATION environment variable or by calling slumber method on configuration object.

While there is an active lock for the key each request trying to read that key will wait in slumber for 2 seconds (configurable by STOCKPILE_SLUMBER environment variable or by calling slumber method on configuration object) and will bypass cache after that if no value will be set in that time.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ConvertKit/stockpile_cache. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the [Apache License Version 2.0] (http://www.apache.org/licenses/LICENSE-2.0).

Code of Conduct

Everyone interacting in the Stockpile project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

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