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35 lines
2.1 KiB
Markdown
35 lines
2.1 KiB
Markdown
# Cassandra on Kubernetes Custom Seed Provider: releases.k8s.io/HEAD
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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.
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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.
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# Configuring the Seed Provider
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The following environment variables may be used to override the default configurations:
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| ENV VAR | DEFAULT VALUE | NOTES |
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| ------------- |:-------------: |:-------------:|
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| KUBERNETES_PORT_443_TCP_ADDR | kubernetes.default.svc.cluster.local | The hostname of the API server |
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| KUBERNETES_PORT_443_TCP_PORT | 443 | API port number |
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| CASSANDRA_SERVICE | cassandra | Default service name for lookup |
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| POD_NAMESPACE | default | Default pod service namespace |
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| K8S_ACCOUNT_TOKEN | /var/run/secrets/kubernetes.io/serviceaccount/token | Default path to service token |
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# Using
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If no endpoints are discovered from the API the seeds configured in the cassandra.yaml file are used.
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# Provider limitations
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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
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expand this capability.
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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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