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Intial draft on SeedProvider docs #24296

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Intial draft on SeedProvider docs #24296

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Intial draft on SeedProvider docs
chrislovecnm Apr 14, 2016
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ran hack/update-generated-docs.sh like I should
chrislovecnm Apr 19, 2016
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62 changes: 62 additions & 0 deletions examples/cassandra/java/README.md
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<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->

<!-- BEGIN STRIP_FOR_RELEASE -->

<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
width="25" height="25">
<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>

If you are using a released version of Kubernetes, you should
refer to the docs that go with that version.

Documentation for other releases can be found at
[releases.k8s.io](http://releases.k8s.io).
</strong>
--

<!-- END STRIP_FOR_RELEASE -->

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# Cassandra on Kubernetes Custom Seed Provider: releases.k8s.io/HEAD

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.

# Configuring the Seed Provider

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 |

# Using


If no endpoints are discovered from the API the seeds configured in the cassandra.yaml file are used.

# Provider limitations

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_](https://docs.datastax.com/en/cassandra/3.x/cassandra/architecture/archSnitchesAbout.html). 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.


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