k8s label selector cheatsheet

k8s 的 label 是關聯 object 之間重要的設定 但在不同地方語法卻會稍微不同 有點惱人
因此整理這篇做紀錄

selector 有兩種

• matchLabels
• matchExpressions

matchLabels

較簡單, 就是 key/value

matchLabels:
  <key>: <value>

matchExpressions

帶有 operator 能夠做出更彈性的設定
多個 Expression 為 and 的關係

matchExpressions:
  - key: ""
    operator: <In|NotIn|Exists|DoesNotExist|Gt|Lt>
    values:
      - ""

Operators

The following are all the logical operators that you can use in the operator field for nodeAffinity and podAffinity mentioned above.

Operator	Behavior
In	The label value is present in the supplied set of strings
NotIn	The label value is not contained in the supplied set of strings
Exists	A label with this key exists on the object
DoesNotExist	No label with this key exists on the object

The following operators can only be used with nodeAffinity.

Operator	Behavior
Gt	The field value will be parsed as an integer, and that integer is less than the integer that results from parsing the value of a label named by this selector
Lt	The field value will be parsed as an integer, and that integer is greater than the integer that results from parsing the value of a label named by this selector

[!NOTE] Gt and Lt operators will not work with non-integer values. If the given value doesn't parse as an integer, the Pod will fail to get scheduled. Also, Gt and Lt are not available for podAffinity.

適用範圍

這就是比較煩的了
不同的 kind 在使用 LabelSelector 可能會使用不同名稱 + 支援不同的 LabelSelector
語法也會不同, 請多利用 kubectl explan 做查詢

kind	field	support LabelSelector
Deployment	selector	matchLabels/matchExpressions
StatefulSet	selector	matchLabels/matchExpressions
Service	selector	matchLabels
NetworkPolicy	podSelector	matchLabels/matchExpressions
PersistentVolume	nodeAffinity	matchExpressions
PersistentVolumeClaim	selector	matchLabels/matchExpressions

Taints and Tolerations

雖不是 label 但設定概念相近

說明可見 taint-and-toleration

# in pod.spec
tolerations:
  - key: ""
    operator: "<Equal|Exists>"
    value: ""
    effect: "<NoExecute|NoSchedule|PreferNoSchedule>"

effect	Behavior
NoExecute	evict pod and no schedule
NoSchedule	no schedule
PreferNoSchedule	soft no schedule