You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
helm/docs/chart_best_practices/pods.md

70 lines
1.7 KiB

# Pods and PodTemplates
This part of the Best Practices Guide discusses formatting the Pod and PodTemplate
portions in chart manifests.
The following (non-exhaustive) list of resources use PodTemplates:
- Deployment
- ReplicationController
- ReplicaSet
- DaemonSet
- StatefulSet
## Images
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".
Images _may_ be defined in the `values.yaml` file to make it easy to swap out images.
```
image: {{ .Values.redisImage | quote }}
```
An image and a tag _may_ be defined in `values.yaml` as two separate fields:
```
image: "{{ .Values.redisImage }}:{{ .Values.redisTag }}"
```
## ImagePullPolicy
`helm create` sets the `imagePullPolicy` to `IfNotPresent` by default by doing the following in your `deployment.yaml`:
```yaml
imagePullPolicy: {{ .Values.image.pullPolicy }}
```
And `values.yaml`:
```yaml
pullPolicy: IfNotPresent
```
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.
## PodTemplates Should Declare Selectors
All PodTemplate sections should specify a selector. For example:
```yaml
selector:
matchLabels:
app: MyName
template:
metadata:
labels:
app: MyName
```
This is a good practice because it makes the relationship between the set and
the pod.
But this is even more important for sets like Deployment.
Without this, the _entire_ set of labels is used to select matching pods, and
this will break if you use labels that change, like version or release date.