Bucket Properties

Riak has bucket properties, which allow individual buckets to take on different behavior as needed. For example, the “posts” bucket may need to be searchable with Riak Search 2.0, or the “indexcache” bucket may not need a high quorum or n-value.

Generally, you do not want to use bucket properties in production with Riak 2. Bucket properties aren’t as efficient as assigning properties to bucket types, and don’t have the same permission restrictions as bucket type properties.


bucket = client.bucket 'pages'
props = Riak::BucketProperties.new bucket
props['r'] #=> 3
props['r'] = 1

The BucketProperties Class

New in the 2.2 version of the Ruby client is the Riak::BucketProperties class. This class provides a Hash-like interface to bucket properties with predictable semantics for when it reads and writes to Riak.

The object is intialized with a Riak::Bucket (or subclass, such as Riak::BucketTyped::Bucket). The Riak::BucketProperties object does not access Riak during initialization.

bucket = client.bucket 'pages'
props = Riak::BucketProperties.new bucket

other_bucket = client.bucket_type('low_redundancy').bucket('page_cache')
other_props = Riak::BucketProperties.new other_bucket

Reading Properties

Accessing a property on the object will hit Riak once:

props['r'] # accesses Riak on first properties load
props['precommit'] # if data are loaded, does not access Riak

The reload method invalidates the cache and will hit Riak on the next property read.


Updating Properties

Updating bucket properties happens in two steps: set the desired values in the BucketProperties instance, and store it into Riak:

props['n_val'] = 1 # stage the value
props.store # write the value, invalidate cache
props['n_val'] # reads the properties from Riak

Special Kinds of Properties

Quorum Values: Integers and Strings

Some quorum values aren’t integers, but a String representing a particular kind of behavior.

Semantics of these values and how replication works can be found in the Replication Properties page of the Riak documentation. Implementation of these aliases is in the BucketPropertiesOperator class inside the BeefcakeProtobuffsBackend, and the enumeration of these property names is in the ProtobuffsBackend superclass.

Hooks and Modfuns

Some bucket properties take a module/function pair, called a “modfun.” These are expressed as a Hash with 'mod' and 'fun' keys.

props['chash_keyfun'] #=> {'mod' => 'riak_core_util', 'fun' => 'chash_std_keyfun'}
props['chash_keyfun'] = {'mod' => 'my_module', 'fun' => 'elite_custom_keyfun'}

Other bucket properties are an array of hooks, and a hook can be either a function name or a modfun.

props['precommit'] #=> [{'mod'=>'validate_json', 'fun'=>'validate'}]
props['precommit'] = [{'mod'=>'my_module', 'fun'=>'vowel_check'}]
props['postcommit'] #=> ['some_name', {'mod'=>'stats', 'fun'=>'update_stats'}]
props['postcommit'] << 'other_name'

The hook properties can be assigned as a modfun hash, but this leads to inconsistent behavior locally:

# Array of Hashes
props['precommit'] #=> [{'mod'=>'validate_json', 'fun'=>'validate'}]

# Assign a singular Hash
props['precommit'] = {'mod'=>'my_module', 'fun'=>'vowel_check'}

# Singular Hash
props['precommit'] #=> {'mod'=>'my_module', 'fun'=>'vowel_check'}


# Array of Hashes
props['precommit'] #=> [{'mod'=>'my_module', 'fun'=>'vowel_check'}]