Within any deployment of Cassandra a Seed Provider is used to for node discovery and communication. When a Cassandra node first starts it must discover which nodes, or seeds, for the information about the Cassandra nodes in the ring / rack / datacenter.
This Java project provides a custom Seed Provider which communicates with the Kubernetes API to discover the required information. This provider is bundled with the Docker provided in this example.
The following environment variables may be used to override the default configurations:
| ENV VAR | DEFAULT VALUE | NOTES |
|---|---|---|
| KUBERNETES_PORT_443_TCP_ADDR | kubernetes.default.svc.cluster.local | The hostname of the API server |
| KUBERNETES_PORT_443_TCP_PORT | 443 | API port number |
| CASSANDRA_SERVICE | cassandra | Default service name for lookup |
| POD_NAMESPACE | default | Default pod service namespace |
| K8S_ACCOUNT_TOKEN | /var/run/secrets/kubernetes.io/serviceaccount/token | Default path to service token |
If no endpoints are discovered from the API the seeds configured in the cassandra.yaml file are used.
This Cassandra Provider implements SeedProvider. and utilizes SimpleSnitch. This limits a Cassandra Ring to a single Cassandra Datacenter and ignores Rack setup. Datastax provides more documentation on the use of SNITCHES. Further development is planned to
expand this capability.
This in affect makes every node a seed provider, which is not a recommended best practice. This increases maintenance and reduces gossip performance.