Abstract

An Archetype field storage which uses a cassandra backing store.

Reasoning

For a customer project I’m doing right now I’m using cassandra as a storage backend for Plone FormGen data. Now the need did arise to also have specific fields of AT content types to be stored in cassandra as well.

Design decisions

• configuration of the cassandra clients done by using plone.app.registry

• per-field configurable keyspace and column family for fields

• The UID of the instance object is used as a key in the specified column family (remember that an insert in cassandra is essentially an update)

• using pycassa as glue library

Usage

Import the storage and attach it to a field in your AT Schema:

from collective.atcassandrastorage.storage import CassandraFieldStorage

MySchema = atapi.Schema(
      ...
      StringField("afield",
              storage=CassandraFieldStorage("AKeyspace", "AColumnFamily"),
              ),
      ...
)

This will store and fetch data for afield from a cassandra database using the keyspace AKeyspace and the column family AColumnFamily.

Configuration

Configuration is done using plone.app.registry. Visit the registry in Plone’s control panel and configure the values, they should be pretty much obvious.

Dependencies

plone.app.registry

for configuration

pycassa

python Cassandra glue library

Links

cassandra

http://cassandra.apache.org/

archetypes

http://plone.org/products/archetypes

pycassa

http://github.com/vomjom/pycassa

Changelog