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20138af37a
Changes the link from my outdated fork to the official Helm chart which is now up to date.
54 lines
2.9 KiB
ReStructuredText
54 lines
2.9 KiB
ReStructuredText
.. _kubernetes:
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Using Patroni with Kubernetes
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=============================
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Patroni can use Kubernetes objects in order to store the state of the cluster and manage the leader key. That makes it
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capable of operating Postgres in Kubernetes environment without any consistency store, namely, one doesn't
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need to run an extra Etcd deployment. There are two different type of Kubernetes objects Patroni can use to store the
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leader and the configuration keys, they are configured with the `kubernetes.use_endpoints` or `PATRONI_KUBERNETES_USE_ENDPOINTS`
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environment variable.
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Use Endpoints
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-------------
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Despite the fact that this is the recommended mode, it is turned off by default for compatibility reasons. When it is on, Patroni stores
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the cluster configuration and the leader key in the `metadata: annotations` fields of the respective `Endpoints` it creates.
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Changing the leader is safer than when using `ConfigMaps`, since both the annotations, containing the leader information, and the actual addresses
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pointing to the running leader pod are updated simultaneously in one go.
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Use ConfigMaps
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--------------
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In this mode, Patroni will create ConfigMaps instead of Endpoints and store keys inside meta-data of those ConfigMaps.
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Changing the leader takes at least two updates, one to the leader ConfigMap and another to the respective Endpoint.
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There are two ways to direct the traffic to the Postgres master:
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- use the `callback script <https://github.com/zalando/patroni/blob/master/kubernetes/callback.py>`_ provided by Patroni
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- configure the Kubernetes Postgres service to use the label selector with the `role_label` (configured in patroni configuration).
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Note that in some cases, for instance, when running on OpenShift, there is no alternative to using ConfigMaps.
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Configuration
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-------------
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Patroni Kubernetes :ref:`settings <kubernetes_settings>` and :ref:`environment variables <kubernetes_environment>` are described in the general chapters of the documentation.
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Examples
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--------
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- The `kubernetes <https://github.com/zalando/patroni/tree/master/kubernetes>`__ folder of the Patroni repository contains
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examples of the Docker image, the Kubernetes manifest and the callback script in order to test Patroni Kubernetes setup.
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Note that in the current state it will not be able to use PersistentVolumes because of permission issues.
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- You can find the full-featured Docker image that can use Persistent Volumes in the
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`Spilo Project <https://github.com/zalando/spilo>`_.
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- There is also a `Helm chart <https://github.com/kubernetes/charts/tree/master/incubator/patroni>`_
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to deploy the Spilo image configured with Patroni running using Kubernetes.
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- In order to run your database clusters at scale using Patroni and Spilo, take a look at the
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`postgres-operator <https://github.com/zalando-incubator/postgres-operator>`_ project. It implements the operator pattern
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to manage Spilo clusters.
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