kubernetes
/
website
mirror of https://github.com/kubernetes/website.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Update PDB documentation to explain new field (#3885) 

* update-docs-pdb

* Addressed erictune@'s comments
reviewable/pr4151/r1
Anirudh Ramanathan 2017-06-20 16:33:44 -07:00 committed by Andrew Chen
parent 76cb30a271
commit 09bf855b76
1 changed files with 59 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
docs/tasks/administer-cluster/configure-pod-disruption-budget.md
View File

@ -1,6 +1,9 @@
--- ---
assignees: assignees:
- davidopp - davidopp
- erictune
- foxish
- kow3ns
title: Configure a Pod Disruption Budget title: Configure a Pod Disruption Budget
redirect_from: redirect_from:
- "/docs/admin/disruptions/" - "/docs/admin/disruptions/"
@ -40,13 +43,37 @@ disruption budget to be violated.
## Specifying a PodDisruptionBudget ## Specifying a PodDisruptionBudget
A `PodDisruptionBudget` has two components: a label selector `selector` to specify the set of A `PodDisruptionBudget` has three fields:
pods to which it applies, and `minAvailable` which is a description of the number of pods from that
* A label selector `selector` to specify the set of
pods to which it applies. This is a required field.
* `minAvailable` which is a description of the number of pods from that
set that must still be available after the eviction, i.e. even in the absence set that must still be available after the eviction, i.e. even in the absence
of the evicted pod. `minAvailable` can be either an absolute number or a percentage. of the evicted pod. `minAvailable` can be either an absolute number or a percentage.
So for example, 100% means no voluntary evictions from the set are permitted. In * `maxUnavailable` (available in Kubernetes 1.7 and higher) which is a description
typical usage, a single budget would be used for a collection of pods managed by of the number of pods from that set that can be unavailable after the eviction.
a controller—for example, the pods in a single ReplicaSet. It can also be either an absolute number or a percentage.
You can specify only one of `maxUnavailable` and `minAvailable` in a single `PodDisruptionBudget`.
`maxUnavailable` can only be used to control the eviction of pods
that have an associated controller managing them. In the examples below, "desired replicas"
is the `scale` of the controller managing the pods being selected by the
`PodDisruptionBudget`.
Example 1: With a `minAvailable` of 5, evictions will be allowed as long as they leave behind
5 or more healthy pods among those selected by the PodDisruptionBudget's `selector`.
Example 2: With a `minAvailable` of 30%, evictions will be allowed as long as at least 30%
of the number of desired replicas are healthy.
Example 3: With a `maxUnavailable` of 5, evictions will be allowed as long as there are at most 5
unhealthy replicas among the total number of desired replicas.
Example 4: With a `maxUnavailable` of 30%, evictions will be allowed as long as no more than 30%
of the desired replicas are unhealthy.
In typical usage, a single budget would be used for a collection of pods managed by
a controller—for example, the pods in a single ReplicaSet or StatefulSet.
Note that a disruption budget does not truly guarantee that the specified Note that a disruption budget does not truly guarantee that the specified
number/percentage of pods will always be up. For example, a node that hosts a number/percentage of pods will always be up. For example, a node that hosts a
@ -55,9 +82,15 @@ specified in the budget, thus bringing the number of available pods from the
collection below the specified size. The budget can only protect against collection below the specified size. The budget can only protect against
voluntary evictions, not all causes of unavailability. voluntary evictions, not all causes of unavailability.
You can find an example of a pod disruption budget defined below. It matches pods with the label A `maxUnavailable` of 0% (or 0) or a `minAvailable` of 100% (or equal to the
number of replicas) may block node drains entirely. This is permitted as per the
semantics of `PodDisruptionBudget`.
You can find examples of pod disruption budgets defined below. They match pods with the label
`app: zookeeper`. `app: zookeeper`.
Example PDB Using maxUnavailable:
```yaml ```yaml
apiVersion: policy/v1beta1 apiVersion: policy/v1beta1
kind: PodDisruptionBudget kind: PodDisruptionBudget
@ -70,8 +103,28 @@ spec:
app: zookeeper app: zookeeper
``` ```
Example PDB Using maxUnavailable (Kubernetes 1.7 or higher):
```yaml
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
name: zk-pdb
spec:
maxUnavailable: 1
selector:
matchLabels:
app: zookeeper
```
For example, if the above `zk-pdb` object selects the pods of a StatefulSet of size 3, both
specifications have the exact same meaning. The use of `maxUnavailable` is recommended as it
automatically responds to changes in the number of replicas of the corresponding controller.
## Requesting an eviction ## Requesting an eviction
See the task explaining [draining nodes](/docs/tasks/administer-cluster/safely-drain-node/) for a higher level construct used to trigger evictions of pods on chosen nodes.
If you are writing infrastructure software that wants to produce these voluntary If you are writing infrastructure software that wants to produce these voluntary
evictions, you will need to use the eviction API. The eviction subresource of a evictions, you will need to use the eviction API. The eviction subresource of a
pod can be thought of as a kind of policy-controlled DELETE operation on the pod pod can be thought of as a kind of policy-controlled DELETE operation on the pod