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openstack-helm/doc/source/devref/getting-started/pod-disruption-budgets.rst
Steve Wilkerson 8846925640 Documentation reorganization and cleanup
This removes empty documentation pages and places the
troubleshooting docs to the top of the docs/source tree. Also
places the pod disruption budget docs to the rest of the
getting-started docs, which are primarily concepts used in
openstack-helm

Change-Id: Ic3f8deefbd873ae5332e14a12351d9967eb22b1b
2017-07-03 12:06:17 -05:00

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=====================
Kubernetes Operations
=====================
Init-Containers
===============
Jobs
====
Pod Disruption Budgets
======================
OpenStack-Helm leverages PodDistruptionBudgets to enforce quotas
that ensure that a certain number of replicas of a pod are available
at any given time. This is particularly important in the case when a Kubernetes
node needs to be drained.
These quotas are configurable by modifying the ``minAvailable`` field
within each PodDistruptionBudget manifest, which is conveniently mapped
to a templated variable inside the ``values.yaml`` file.
The ``min_available`` within each service's ``values.yaml`` file can be
represented by either a whole number, such as ``1``, or a percentage,
such as ``80%``. For example, when deploying 5 replicas of a pod (such as
keystone-api), using ``min_available: 3`` would enfore policy to ensure at
least 3 replicas were running, whereas using ``min_available: 80%`` would ensure
that 4 replicas of that pod are running.
**Note:** The values defined in a PodDisruptionBudget may
conflict with other values that have been provided if an operator chooses to
leverage Rolling Updates for deployments. In the case where an
operator defines a ``maxUnavailable`` and ``maxSurge`` within an update strategy
that is higher than a ``minAvailable`` within a pod disruption budget,
a scenario may occur where pods fail to be evicted from a deployment.