Kubernetes - ReplicationController

  A ReplicationController ensures that a specified number of pod replicas are running at any one time. In other words, a ReplicationController makes sure that a pod or a homogeneous set of pods is always up and available.

How a ReplicationController Works

If there are too many pods, the ReplicationController terminates the extra pods. If there are too few, the ReplicationController starts more pods. Unlike manually created pods, the pods maintained by a ReplicationController are automatically replaced if they fail, are deleted, or are terminated. For example, your pods are re-created on a node after disruptive maintenance such as a kernel upgrade. For this reason, you should use a ReplicationController even if your application requires only a single pod.


LAB


1. Replication Controller YAML file


# nginx-rc.yaml  

apiVersion: v1
kind: ReplicationController
metadata:
  name: nginx-rc
spec:
  replicas: 3
  template:
    metadata:
      name: nginx-pod
      labels:
        app: nginx-app
    spec:
      containers:
      - name: nginx-container
        image: nginx
        ports:
        - containerPort: 80
  selector:
    app: nginx-app



*******************************************************************

# 2. Create and display


kubectl create -f nginx-rc.yaml

kubectl get po -o wide

kubectl get po -l app=nginx-app

kubectl get rc nginx-rc

kubectl describe rc nginx-rc


*******************************************************************

# 3. Reschedule


kubectl get po -o wide --watch

kubectl get po -o wide

kubectl get nodes


*******************************************************************

# 4. Scaling up cluster


kubectl scale rc nginx-rc --replicas=5

kubectl get rc nginx-rc

kubectl get po -o wide


*******************************************************************

# 5. Scalling down


kubectl scale rc nginx-rc --replicas=3

kubectl get rc nginx-rc

kubectl get po -o wide


*******************************************************************

# 6. Cleanup


kubectl delete -f nginx-rc.yaml

kubectl get rc

kubectl get po -l app=nginx-app

Comments

Post a Comment

Popular posts from this blog

Terraform

Image
  Terraform is an infrastructure as code tool that lets you build, change, and version cloud and on-prem resources safely and efficiently. HashiCorp Terraform is an infrastructure as code tool that lets you define both cloud and on-prem resources in human-readable configuration files that you can version, reuse, and share. You can then use a consistent workflow to provision and manage all of your infrastructure throughout its lifecycle. Terraform can manage low-level components like compute, storage, and networking resources, as well as high-level components like DNS entries and SaaS features. How does Terraform work? Terraform creates and manages resources on cloud platforms and other services through their application programming interfaces (APIs). Providers enable Terraform to work with virtually any platform or service with an accessible API. HashiCorp and the Terraform community have already written  thousands of providers  to manage many different types of resources...
Read more

Different Types of Reports in Scrum - Agile

Image
  Introduction to Agile Reporting I’m not going to elaborate on the Agile Framework itself here.  1. Sprint Burndown At a Sprint-level, the burndown presents the  easiest way to track and report status  (the proverbial  Red / Amber / Green ), i.e., whether your Sprint is on or off-track, and what are the chances of meeting the Sprint goals. The burndown chart – when used right – can provide  near-real time updates  on Sprint progress. “If your team do it right, then they would take in just the right amount of work into a sprint.” At the beginning of a Sprint, the Scrum team perform Sprint Planning and agree to take on development work worth a certain number of Story points. This forms the basis for the Sprint Burndown chart. The total story points agreed at the beginning of the sprint make up the y-axis, and the individual dates in the Sprint make up x-axis. If your team do it right, then they would take in just the right amount of work into ...
Read more

Scrum Master Interview help - Bootcamp

Understanding the MoSCoW prioritization | How to implement it into your project Projects, irrespective of their size or complexity, often juggle numerous tasks and requirements. In such a scenario,  MoSCoW prioritization  becomes essential to ensure the successful completion of the project.  Besides, it is also a very effective way to manage project priorities. With a straightforward and adaptable approach, the MoSCoW method helps manage stakeholder expectations and improve project outcomes. What is the MoSCoW prioritization technique?  The MoSCoW method is a prioritization matrix widely used in project management and software development. The term MoSCoW is an acronym that stands for  Must have ,  Should have ,  Could have , and  Won’t have , each denoting a level of priority. Here is the breakdown of the MoSCoW method:  Must have:  These are critical requirements that the project cannot be completed withou...
Read more