redis_failover-rails

An ActiveSupport::Cache store using redis_failover (a zookeeper based implementation of HA redis) for Rails apps.

This is based on the work done by @wr0ngway (Matt Conway), available on redis_failover_example.

Also, this gem utilizes redis_failover, a gem that creates a Redis HA implementation, using zookeeper for mantaining the available nodes. This can be found on redis_failover.

Requirements

In order to work, this requires a working redis_failover implementation. Please follow the instructions on the gem and ask your favourite Sysadmin/DevOps to implement in your environment.

Considerations

In case you don't have a redis_failover implementation working, and for helping in the development process, this also works with a single node redis server. Just don't specify zkservers in the config file.

Installation

Just add the dependency to your Gemfile...

# Gemfile
gem 'redis_failover-rails'

and run bundle install.

bundle install

NOTE: If you are running passenger or unicorn, you definitely want to add this to your config/initializers/passenger.rb of your app.

This is THIS IS VERY IMPORTANT IN PRODUCTION ENVIRONMENTS!!

if defined?(PhusionPassenger)
  PhusionPassenger.on_event(:starting_worker_process) do |forked|
    if forked
      # We're in smart spawning mode.

      # Reset redis failover clients
      RedisFactory.reconnect
    end
  end
end

This generates a reconnect after the app is forked so the redis clients get reset.

Usage

In your application.rb (or environment), you should use something like:

config.cache_store = :redis_cache_store, :cache
config.cache_classes = true
config.action_controller.perform_caching = true

Testing

In order to make your tests work, you need a working redis_failover installation, with Redis, Zookeeper and Node Manager running on the ports specified in the default config file.

Also you need a single redis server running on port 6379.

For running the tests, just:

bundle exec rake

Configuration

In order to define your redis and redis_failover configurations, you just need to use the redis.yml config file

This is mandatory at the moment of integrating the gem with your Rails app, there are no defaults. The existing config file in the repo is used for tests only, when you run the gem inside the Rails app, it tries to find the proper redis.yml file and if it doesn't exist, the app just doesn't start.

This follows a format like this:

environment:
  instance:
    parameter1: value1
    parameter2: value2

This gem automatically selects a redis_failover client if you define :zkservers in the config file. If not, it just uses the standard redis client.

This are the options available if you configure a redis_failover client:

:zk            - an existing ZK client instance
:zkservers     - comma-separated ZooKeeper host:port pairs
:znode_path    - the Znode path override for redis server list (optional)
:password      - password for redis nodes (optional)
:db            - db to use for redis nodes (optional)
:namespace     - namespace for redis nodes (optional)
:logger        - logger override (optional)
:retry_failure - indicate if failures should be retried (default true)
:max_retries   - max retries for a failure (default 3)
:safe_mode     - indicates if safe mode is used or not (default true)
:master_only   - indicates if only redis master is used (default false)
:verify_role   - verify the actual role of a redis node before every command (default true)

Typical configuration parameters for standard redis clients are:

:host          - Redis server host
:port          - Redis server port
:db            - Redis database to use
:password      - Redis connection password

Please keep in mind that this options are not validated, just passed to the client configuration.

Basic redis.yml examples:

# Standard redis
development:
  cache:
    host: localhost
    port: 6379
    db: 1

# HA redis_failover in development
production:
  hacache:
    thread_safe: true
    zkservers: localhost:2181, localhost:2182, localhost:2183
    db: 1
    znode_path: /redis_failover   #sometimes required...

# HA redis_failover for a production environment
production:
  hacache:
    thread_safe: true
    zkservers: zk-1:2181, zk-2:2181, zk-3:2181
    db: 1
    znode_path: /redis_failover   #sometimes required...

License

This gem is released with MIT licensing. Please see LICENSE for details.

Author

Initially created by Jose Pettoruti - @jepettoruti for Surfdome.com

Acknowledgements

This couldn't have been achieved without the work of @ryanlecompte for making the amazing redis_failover gem.

Special thanks to @wr0ngway for his example on how to implement this on Rubber.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request