ReplicaSet.md

ReplicaSet In Kubernets

Replica Set is enhance version of Replication Controller

ReplicaSet’s purpose is to maintain a stable set of replica Pods running at any given time.

Difference between Replication controller vs ReplicaSet

ReplicaSet :-

Replica Set : Replica Set supports the new set-based selector. This gives more flexibility. Ex. environment in (production, qa) This selects all resources with key equal to environment and equal to production or qa

Replication Controller : Replication Controller only supports equality-based selector. Ex. environment = production This selects all resources with key equal to environment and value equal to production

Operators to use with ReplicaSets

There are three kinds of operator we can use with ReplicaSets:

• In
• Notin
• Exists

MatchLabels ReplicaSet Example

apiVersion: apps/v1  # our API version
kind: ReplicaSet # # The kind we are creating
metadata: # Specify all Metadata like name, labels
 name: frontend
 labels:
   app: myReplica
spec:
  replicas: 3 # Here is where we tell k8s how many replicas we want
  selector:   # This is our label selector field. 
    matchLabels: 
      app: frontend   # we are using the Equality based operators
  template:
    metadata:
      labels:
        app: frontend   
    spec:
      containers:  
        - name: php-redis
          image: gcr.io/google_samples/gb-frontend:v3
          
          
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Creating normal pod 

apiVersion: v1
kind: Pod
metadata:
  name: pod1
  labels:
    app: frontend
spec:
  containers:
  - name: hello1
    image: gcr.io/google-samples/hello-app:2.0
---
apiVersion: v1
kind: Pod
metadata:
  name: pod2
  labels:
    app: frontend
spec:
  containers:
  - name: hello2
    image: gcr.io/google-samples/hello-app:1.0
		  

Match Selector

apiVersion: apps/v1  # our API version
kind: ReplicaSet # # The kind we are creating
metadata: # Specify all Metadata like name, labels
 name: frontend
 labels:
   app: frontend
spec:
  replicas: 3 # Here is where we tell k8s how many replicas we want
  selector:   # This is our label selector field.
    matchExpressions:
      - key: app1
        operator: In
        values:
         - qa
  template:
    metadata:
      labels:
        app1: qa
    spec:
      containers:
        - name: php-redis
          image: gcr.io/google_samples/gb-frontend:v3
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Creating normal Pods 

Creating normal pod 

apiVersion: v1
kind: Pod
metadata:
  name: pod1
  labels:
    Enviourment: qa
spec:
  containers:
  - name: hello1
    image: gcr.io/google-samples/hello-app:2.0
---
apiVersion: v1
kind: Pod
metadata:
  name: pod2
  labels:
    Enviourment: test
spec:
  containers:
  - name: hello2
    image: gcr.io/google-samples/hello-app:1.0