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70 lines
1.7 KiB
70 lines
1.7 KiB
# Pods and PodTemplates
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This part of the Best Practices Guide discusses formatting the Pod and PodTemplate
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portions in chart manifests.
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The following (non-exhaustive) list of resources use PodTemplates:
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- Deployment
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- ReplicationController
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- ReplicaSet
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- DaemonSet
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- StatefulSet
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## Images
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A container image should use a fixed tag or the SHA of the image. It should not use the tags `latest`, `head`, `canary`, or other tags that are designed to be "floating".
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Images _may_ be defined in the `values.yaml` file to make it easy to swap out images.
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```
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image: {{ .Values.redisImage | quote }}
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```
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An image and a tag _may_ be defined in `values.yaml` as two separate fields:
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```
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image: "{{ .Values.redisImage }}:{{ .Values.redisTag }}"
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```
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## ImagePullPolicy
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`helm create` sets the `imagePullPolicy` to `IfNotPresent` by default by doing the following in your `deployment.yaml`:
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```yaml
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imagePullPolicy: {{ .Values.image.pullPolicy }}
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```
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And `values.yaml`:
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```yaml
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pullPolicy: IfNotPresent
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```
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Similarly, Kubernetes defaults the `imagePullPolicy` to `IfNotPresent` if it is not defined at all. If you want a value other than `IfNotPresent`, simply update the value in `values.yaml` to your desired value.
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## PodTemplates Should Declare Selectors
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All PodTemplate sections should specify a selector. For example:
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```yaml
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selector:
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matchLabels:
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app.kubernetes.io/name: MyName
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template:
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metadata:
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labels:
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app.kubernetes.io/name: MyName
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```
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This is a good practice because it makes the relationship between the set and
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the pod.
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But this is even more important for sets like Deployment.
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Without this, the _entire_ set of labels is used to select matching pods, and
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this will break if you use labels that change, like version or release date.
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