Login
May 29, 2023|
Voiced by Amazon Polly |
Introduction
Deployment strategies are part of Deployments, which helps scale the application efficiently without downtime. We can also revert to the previous application version with the help of deployments. And ReplicaSet helps in maintaining the desired replicas of applications.
What is ReplicaSet?
A ReplicaSet is a Kubernetes object that manages a group of pods. It ensures that the number of pods in the group always matches the desired number.
Image Source: https://blog.devgenius.io/k8s-controller-replicaset-e6e0f29312f1
Pioneers in Cloud Consulting & Migration Services
- Reduced infrastructural costs
- Accelerated application deployment
Features of Replica Set
- A pod template is used to create a new pod whenever an existing pod fails, and the replica count is maintained by defining the desired number of replicas a controller needs to be running.
- A replica set also ensures that an additional pod needs to be created or deleted whenever an instance with the same label is created.
- The replica set allows multiple pod replicas, which means the traffic is sent to different instances, preventing overloading a single instance.
- The replica set ensures it has multiple replicas of the application so that it won’t fail because of one pod fails.
ReplicaSet Manifest
Below is the YAML file, which will create multi replicas of the pod.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 |
apiVersion: apps/v1 kind: ReplicaSet metadata: name: httpd-replica namespace: facebook spec: replicas: 4 minReadySeconds: 10 selector: matchLabels: role: web matchExpressions: - {key: version, operator: In, values: [v1, v2, v3]} template: metadata: name: web labels: role: web version: v1 tier: frond spec: containers: - name: web image: httpd ports: - containerPort: 80 protocol: TCP |
Fields that are used to define replicas are as follows:
- Selector:It is used to identify for which pod the replica set is responsible.
- Replicas:It specifies the number of pods the replica set must maintain.
- Template:It defines the pod template replica set that will use to create new pods.
- ApiVersion:It defines Kubernetes API that supports ReplicaSet.
What is Deployment and its strategies?
Deployment is used to maintain the versions of your application running in the pod. It helps to scale the number of replica pods efficiently and enables the rollout and rollback to an earlier deployment version. Deployment runs on multiple replicas of the pod and automatically replaces a pod in case of any failure or unresponsiveness. Deployments are Kubernetes object that helps to keep your application running. They do this by creating and managing Pods, the basic deployment units in Kubernetes.
A Deployment uses a Pod template to define the desired state of its Pods. The Pod template specifies the containers that should run in each Pod, the volumes that should be mounted, and the labels that should be applied. When a Deployment’s Pod template changes, new Pods are automatically created one at a time.
Image Source: https://scoutapm.com/blog/kubernetes-uses-and-introduction
What are Rolling Updates and Recreate Strategies in Deployments?
The rolling update provides an orderly migration from one version to a newer version. The rolling update is used in such situations when a new version of an application comes, and you have to switch to a newer version. In the rolling update, all the running pods will be replaced with the newer application version by systematically terminating the older version of the application pods.
A recreate deployment strategy is an all-or-nothing process that lets you update an application immediately, with some downtime. With this strategy, existing pods from the deployment are terminated and replaced with a new version. This means the application experiences downtime from the time the old version goes down until the new pods start successfully and start serving user requests.
Deployment with ReplicaSet
Deployments are generally used with the replicaset as they are used to manage replicsets. With the help of deployment, you can roll back to a previous Deployment revision. You have the option to utilize a Deployment while managing a ReplicaSet. With a Deployment, you can generate a fresh version of a ReplicaSet and transfer the current pods from an older version to the new one. Subsequently, the Deployment is capable of removing outdated and unused ReplicaSets.
So, Replicaset ensures replicas of pods are available, whereas deployment is responsible for managing different versions of the application. For deployment, the replica set can’t rollout or rollback to different application versions nor maintain any revisions.
Deployment Manifest with strategy
Below is the yaml file for Deployment.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 |
apiVersion: apps/v1 kind: Deployment metadata: name: nginx namespace: facebook spec: strategy: type: RollingUpdate #Bydefault (RollingUpdate/Recreate) rollingUpdate: maxSurge: 2 maxUnavailable: 1 revisionHistoryLimit: 10 paused: false replicas: 3 minReadySeconds: 10 selector: matchLabels: role: webserver jane: akil matchExpressions: - {key: version, operator: In, values: [v1, v2, v3]} template: metadata: name: web labels: role: webserver version: v3 tier: frond jane: akil spec: containers: - name: web image: nginx:1.20-perl ports: - containerPort: 80 protocol: TCP |
Key elements of the above YAML file:
- We are creating a deployment type file Strategy which means if any changes are there, it will apply them.
- The Rolling Update will check if the container serves any request. After the request is served, it will apply the changes.
- A revision history limit means several changes that can perform. It will keep track of all revisions in the form of revisions.
- MaxSurge means whenever a revision is applied, it will create a specified number of containers according to the values given it will apply it to the pod.
Conclusion
Deployments and ReplicaSet are an important component of Kubernetes, which helps you not only deploy your application but also helps manage replicas of your pods. And with deployments, you can perform rolling updates and maintain different versions of your application.
Making IT Networks Enterprise-ready – Cloud Management Services
- Accelerated cloud migration
- End-to-end view of the cloud environment
About CloudThat
CloudThat is an official AWS (Amazon Web Services) Advanced Consulting Partner and Training partner and Microsoft Gold Partner, helping people develop knowledge of the cloud and help their businesses aim for higher goals using best in industry cloud computing practices and expertise. We are on a mission to build a robust cloud computing ecosystem by disseminating knowledge on technological intricacies within the cloud space. Our blogs, webinars, case studies, and white papers enable all the stakeholders in the cloud computing sphere.
Drop a query if you have any questions regarding Deployment Strategy and I will get back to you quickly.
To get started, go through our Consultancy page and Managed Services Package that is CloudThat’s offerings.
FAQs
1. What is the major difference between ReplicaSet and Deployment?
ANS: – While a ReplicaSet guarantees the presence of a designated count of pod replicas, a Deployment operates at a higher level and oversees ReplicaSets while offering declarative updates to Pods and various other beneficial functionalities.
2. What is the major difference between ReplicationController and Deployment?
ANS: – The recommended approach for replication now involves utilizing a Deployment to configure a ReplicaSet. A ReplicationController maintains a designated number of pod replicas, ensuring constant pod availability or a homogeneous group of pods.
WRITTEN BY Shubh Dadhich
PREV
Comments