Kubernetes Labels and Selector

CozyFex included in kubernetes k8s orchestration

2021-05-10 340 words 2 minutes

Contents

Labels

POD A-frt

Key	Value
app	frontend
color	red
shape	triangle

POD B-fyt

Key	Value
app	frontend
color	yellow
shape	triangle

POD C-fgt

Key	Value
app	frontend
color	green
shape	triangle

POD D-brt

Key	Value
app	backend
color	red
shape	triangle

POD E-byt

Key	Value
app	backend
color	yellow
shape	triangle

POD F-bgt

Key	Value
app	backend
color	green
shape	triangle

POD G-frr

Key	Value
app	frontend
color	red
shape	rectangle

POD H-byr

Key	Value
app	backend
color	yellow
shape	rectangle

POD I-bgr

Key	Value
app	backend
color	green
shape	rectangle

Selector

Selector 1

1
kubectl get pods --selector app=backend,shape=rectangle

Key	Value
app	backend
shape	rectangle

Selected PODs by Selector 1

POD
POD H-byr
POD I-bgr

Selector 2

1
kubectl get pods --selector app=frontend,color=red

Key	Value
app	frontend
color	red

Selected PODs by Selector 2

POD
POD A-frt
POD G-frr

Selector 3

1
kubectl get pods --selector color=green,shape=rectangle

Key	Value
color	green
shape	rectangle

Selected PODs by Selector 2

POD
POD I-bgr

YAML

_{replicaset-definition.yml}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: simple-webapp
  labels:
    app: App1
    function: Front-end
spec:
  replicas: 3
  selector: # -> This selector is matching below labels in template.
    matchLabels:
      app: App1
  template:
    metadata:
      labels:
        app: App1
        function: Front-end
    spec:
      containers:
        - name: simple-webapp
          image: simple-webapp

_{service-definition.yml}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector: # -> This selector is find ReplicaSet and PODs.
    app: App1
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376

Annotations Example

_{replicaset-annotation-definition.yml}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: simple-webapp
  labels:
    app: App1
    function: Front-end
  annotations:
    buildVersion: 1.34
spec:
  replicas: 3
  selector: # -> This selector is matching below labels in template.
    matchLabels:
      app: App1
  template:
    metadata:
      labels:
        app: App1
        function: Front-end
    spec:
      containers:
        - name: simple-webapp
          image: simple-webapp