IMPORTANT: If you are reading this on the main ActiveColumn page on github, please go to the actual README page so that links bring you to the right place.
ActiveColumn is a framework for working with data in Cassandra. It currently includes two features:
- Database migrations
- "Time line" model data management
Data migrations are very similar to those in ActiveRecord, and are documented in Migrate.
Time line data management is loosely based on concepts in ActiveRecord, but is adapted to saving data in which rows in Cassandra grow indefinitely over time, such as in the oft-used Twitter example for Cassandra. This usage is documented in:
Add ActiveColumn to your Gemfile:
Install with bundler:
ActiveColumn requires Cassandra 0.7 or above, as well as the cassandra gem, version 0.9 or above. You must also be sure to use the Cassandra 0.7 support in the gem, which can be done by adding Cassandra to your Gemfile like this:
gem 'cassandra', '>= 0.9', :require => 'cassandra/0.7'
Data migrations in ActiveColumn are used within a Rails project, and are driven off of a configuration file, config/cassandra.yml. It should look something like this:
test: servers: "127.0.0.1:9160" keyspace: "myapp_test" thrift: timeout: 3 retries: 2 development: servers: "127.0.0.1:9160" keyspace: "myapp_development" thrift: timeout: 3 retries: 2
You can use embedded ruby code in the YAML file to determine host/machine specific settings.
production: servers: "<%=get_from_file('abc.conf')%>:9160" keyspace: "<%=get_from_file('abc.conf')%>" disable_node_auto_discovery: true thrift: timeout: 3 retries: 2
Node Auto Discovery
You can set disable_node_auto_discovery to off by setting disable_node_auto_discovery flag in your cassandra.yml
In order to get time line modeling support, you must provide ActiveColumn with an instance of a Cassandra object. Since you have your cassandra.yml from above, you can do this very simply like this:
config = YAML.load_file(Rails.root.join("config", "cassandra.yml"))[Rails.env] $cassandra = Cassandra.new(config['keyspace'], config['servers'], config['thrift']) ActiveColumn.connection = $cassandra
As you can see, I create a global $cassandra variable, which I use in my tests to validate data directly in Cassandra.
Add column family
create_column_family :impressions do |cf| cf.comment = 'impressions for something' cf.comparator_type = :utf8 cf.key_validation_class = :utf8 end
Drop column family
Rename column family
rename_column_family :impressions, :showings
Update column family
update_column_family :impressions do |cf| cf.comment = "blah" cf.gc_grace_seconds = 3600 end
One other thing to note is that you obviously must have Cassandra installed and running! Please take a look at the mama_cass gem for a quick way to get up and running with Cassandra for development and testing.