Cassandra is a distributed (peer-to-peer) system for the management and
storage of structured data.
The Apache Cassandra database is the right choice when you need scalability
and high availability without compromising performance. Linear scalability
and proven fault-tolerance on commodity hardware or cloud infrastructure
make it the perfect platform for mission-critical data. Cassandra's support
for replicating across multiple datacenters is best-in-class, providing lower
latency for your users and the peace of mind of knowing that you can survive
Cassandra's ColumnFamily data model offers the convenience of column indexes
with the performance of log-structured updates, strong support for materialized
views, and powerful built-in caching.
See cassandra.apache.org for more information.
Cassandra deployments are relatively simple in that they consist of a set of
Cassandra nodes which seed from each other to create a ring of servers:
juju deploy precise/cassandra
juju add-unit -n 2 cassandra
The service units will deploy and will form a single ring.
The API to Cassandra is supported through Apache Thrift; Thrift is a software
framework for scalable cross-language services development.
See this documentation for more details of how to use this API.
Cassandra recommend using one of the many client options - see
ClientOptions for more details.
To relate the Cassandra charm to a service that understands how to talk to
Cassandra using thrift::
juju deploy --repository . local:service-that-needs-cassandra
juju add-relation service-that-needs-cassandra cassandra
The cassandra charm supports offline-capable installation (and cross platform installation's) by the use of 'fat-packing' the charm.
Place a cassandra_*.deb in files. During deployment, the cassandra charm checks for the presence of this file, if present, it utilizes that deb resource instead of reaching out over the wire.
You can fetch upstream Cassandra debs: here
Changing the configuration of a deployed Cassandra cluster is supported; however
it will result in a restart of each Cassandra node as the changes are implemented
which may result in outages.
The trusty version of the cassandra charm is completely different than this
charm and may not support the same configuration options as this charm does.
Cassandra has a pretty good guess at configuring its Java memory settings to
fit the machine that it has been deployed on.
The charm does support manual configuration of Java memory settings - see the
config.yaml file for more details::
However be aware that its recommended that Cassandra always remains in 'real'
memory and should never be swapped out to disk so keep this in mind when
changing these options.
Cassandra sets both is minimum and maximum heap size on startup so will
pre-allocate all memory to avoid freezes during operation (this happens
during normal operation as more memory is allocated to heap.
This charm supports installing a different package version than what is in the
Ubuntu software archives. You need to specify multiple options at once.
apt-repo-spec: "deb http://debian.datastax.com/community stable main"
extra_packages: "openjdk-7-jre-headless dsc20=2.0.10-1"