kubernetes-mongodb. In a StatefulSet, each pod is given a name and treated individually, in contrast to a Kubernetes Deployment, where pods are easily replaceable. kubectl create -f hpa-rs . <externalDomain> The replica set controller detected that and created a new Pod to match the replicas' desired number (5). How to initialize replicaset remotely on mongoDB on a Kubernetes environment. mongo. 9. Learn more about TeamsManual replica count adjustment comes with a limitation: scaling down to 0 will create a period of downtime where there's no Pods available to serve your users. cluster. Using YAML file to create ReplicaSet in Kubernetes is quite popular and is also the most preferable way. com, the world's largest job site. strategy: type: Recreate in the deployment spec. The controller that Kubernetes going to create through YAML file will be defined by the parameter kind which will be set as ReplicaSet in this case. In this Kubernetes Tutorial we did a comparison between Replication Controller and Replica Set. Replica Set . His life’s purpose is to deliver good. There are 5 basic steps to run HA PostgreSQL: Chose a a multi-cloud container orchestration platform like Kubernetes. matchLabels field and. yaml # or another way of writing "kubectl scale --replica=10 replicaset <replicaset name as provided in metadata>" kubectl scale --replica=10 replicaset myapp-rs. As with all other Kubernetes API objects, a ReplicaSet needs the apiVersion, kind, and metadata fields. Kind of like a watch dog. You can think as with an RC → app=newsproducer,. Each Node is managed by the Master. The MongoDB replica set can be easily connected with the help of internal ClusterIP within the cluster. Rolling updates also offer the ability to roll back to the previous version if any issues arise during the update process. kubectl scale replicaset nginxset --replicas=4. It ensures that the desired number of replicas (PODs with. kubectl apply -f creates Replica Sets using a config file: kubectl apply -f replicaset-definition-file. The difference comes with the usage of selectors to replicate pods. kubectl get pod,svc -owide NAME READY STATUS. A ReplicaSet is a Kubernetes object that ensures that a specified number of replicas of a pod are running at any given time. StatefulSets. DESIRED CURRENT READY AGEmy-first-replicaset 3 3 3 2m// get in the editor, modify the replica number, then save and leave$ kubectl edit rs my-first-replicaset. He is also a published author and a frequent speaker at international conferences, discussing Java, Kubernetes, Quarkus, Microservices, Cloud Computing, and DevOps. Additionally you can use KEDA for event-driven autoscaling. Add a new controller “MongoDbController”: The code will query and return all collections in the MongoDB replica set. The name of a DaemonSet object must be a valid DNS subdomain name. A Replicaset is a K8s object, a set of Pod templates that describe a set of Pod replicas. For ReplicaSets, the kind is always a ReplicaSet. edit the image name in the editor. in. . You can get the list of configured node ports using the command below: echo "$ (kubectl. Here, I’m scaling down the ReplicaSet used in the article’s example to manage two pods instead of four. Unlike the official MongoDB Operator that manages the cluster through sidecar containers with running agents, the Percona Kubernetes Operator does it directly from its Pod. initiate () You only have to initiate the replica set once. A StatefulSet offers stable network identities and persistent storage for the MongoDB pods. 509 certificates. For example, for a member of a replica set deployed on a Pod with the name rs-mongos-0-0, in the Kubernetes Operator service named mongo-0 that is created in the default mongodb namespace, the FQDN is:Wait for the MongoDB Replica Set to be fully deployed. It can be considered as a replacement of replication controller. The selector is used to identifying the Pods it can acquire. 1. in case have 10 nodes and I use the podAntiAffinity: with the topologyKey and one app with 5 replica, each instance of the 5 pods will be scheduled in different node as each node have diffrent kubernetes. These deployments are useful for working with a large amount of data and high loads. Sep 16, 2022 at 21:35. Pause the cluster on K8s. Ensure that you add s for each Kubernetes pod that hosts a member of your replica set to the certificate. Usually, you define a Deployment and let that Deployment manage ReplicaSets automatically. Replicaset doesnot update pods in when pod image is modified. your pod running, potentially on different nodes in the cluster, a couple of things suddenly become possible: Because there are a number of clones of your pod running, Kubernetes can distribute the load between them. It creates a replica of 4 busybox pods. This is what will be used to set up the replica set on runtime for each pod:1 Answer. 15 and later. Now, let’s write a deployment. Come build a rewarding, meaningful. So, this looks enough for a. As you can see, rather than listing the individual pods, Kubernetes shows us the Replica Set. ReplicaSets are a higher-level API that gives the ability to easily run multiple instances of a given pod. 6. To see the current status of the pods associated with the ReplicaSet, use. Create a folder called /kubernetes_experiments and in that folder run. Create a MongoDB replica set in Kubernetes. Deployments encapsulate replica sets and pods in the Kubernetes’ resource hierarchy and provide a declarative method of updating the state of both. Replication in MongoDB. name=nginx-deployment. 9, la version de l'API apps/v1 pour le type ReplicaSet est la version actuelle et activée par défaut. From my understanding this means that MongoDB cannot connect to the given member. Claire Lee. Writing a ReplicaSet manifest. A simple and short explanation to understand Replication Controller and Replica Set in Kubernetes Services. 5] Kubernetes PODs Concept Else go to → [EP. 1 Answer. This command initializes the replica set, and should only be run on the first replica set member. It acquires new Pods by matching its selector. Logging Stack on Kubernetes to learn how to set up a logging stack with Elasticsearch, Fluentd, and Kibana. the pod template specified inside the Deployment's yaml file, and the value of the replica field (which defines the size of the pod set). So, this looks enough for a replicaSet to check if enough pods are running. Dans Kubernetes 1. These can be. Deployment handles the ReplicaSet, it gets. Specify whether the replica set member votes in elections. yaml -n <namespace-name>. Kubernetes has a concept of "probes": readiness probe to make sure that the pod is up-and-running, liveness probe to make sure that the pod is still going well. Deployments can also specify configuration data, such as which network ports to open for containers . Before you begin StatefulSets are only available in Kubernetes version 1. Going to the Kubernetes Dashboard I can confirm that the deployment was correctly updated with the new metadata. Note that even if running the configuration shown in Figure 3 on a Kubernetes cluster of three or more nodes, Kubernetes may (and often. This limitation comes from MongoDB itself, for more information please check. This chart implements a dynamically scalable MongoDB replica set using Kubernetes StatefulSets and Init Containers. Set the hostnames and ports in spec. 31 (a downgrade but still an update from K8s point of view), the ReplicaSet is not completely replaced. The controllers mentioned in this article, ReplicaSets, Deployments, StatefulSets and. Finally, 3. Example-1: Create replica set using match labels. Replica Set. – Sahadat Hossain. Create the docker image as you did for the MySqlApi project. But when I edit this deployment using the command kubectl edit deployment my-dep2, only changing the version of busybox image to 1. metadata. Wenn Sie eine spezifische, beantwortbare Frage zur Verwendung von Kubernetes haben, stellen Sie diese unter Stack Overflow. metadata. - Created mongo instance in 3 pods. 2. connectivity. Careers. The specification of a replica set looks very much like the specification of a pod, except that it carries a number, indicating how many replicas — i. This application is a replicated MySQL database. To deploy MongoDB as a Replica Set with multiple pods, a Kubernetes StatefulSet deployment will be required. kubectl delete $ (kubectl get all | grep replicaset. By default, the HPA checks the Metrics API every 15 seconds for any required changes in replica count, and the Metrics API retrieves data from the Kubelet every 60 seconds. This approach ensures that all instances of our application use the latest image. Thus, you have one SQL Server instance deployed per pod in the Kubernetes cluster. These correspond to the three nodes in your MongoDB replica set. The functionality of both Replica Controller and Replica Set are quite the same - they are responsible to make sure that X number of pods with label that is equal to there label selector will be scheduled to different nodes on the cluster. 27. Connect to mongodb replicaset in kubernetes with external access enabled. Before you begin You need to have a Kubernetes. Like a Deployment, a StatefulSet manages Pods that are based on an identical container spec. Replication controller is kinda imperative, but replica sets try to be as declarative as possible. In Kubernetes, a HorizontalPodAutoscaler automatically updates a workload resource (such as a Deployment or StatefulSet), with the aim of automatically scaling the workload to match demand. I am looking for help with connecting to a mongo db replica-set , on K8s. The primary is the only member in the replica set that receives write operations. Here we go. 2. svc. g. I have written a bash script to get all deployments on a kubernetes cluster. As such, it is often used to guarantee the availability of a specified number of identical Pods. Writing a ReplicaSet manifest. It consists of a container that has access to an AWS EFS resource. The configuration of the third replica set member follows the same pattern and the following figure shows the complete replica set: **Figure 3:** Full Replica Set member configured as a Kubernetes Service. Replication Controller . It can be on-prem or some virtual machine. Mongodb 6 How To Deploy A Mongodb Replicaset Youtube The process of configuring a mongodb replica set on gke using kubernetes is a simple and uncomplicated one, comprising a handful of steps. This is achieved by creating or removing pod replicas as necessary. For this reason, replica sets are preferred over a. It creates a replica of 4 busybox pods. O verview. default. Modified 8 months ago. local) as the default hostname. A Deployment is a Kubernetes object that manages a set of identical pods, ensuring that a specified number of replicas of the pod are running at any given time. A big advantage of Kubernetes and StatefulSets is that you can scale the number of MongoDB Replicas up and down with a single command! To scale up the number of replica set members from 3 to 5, run this command: kubectl scale --replicas=5 statefulset mongo In a few minutes, there will be 5. In the YAML file, we’ve set the value of spec. vim my-replica-set. 1. 10 <none> 53/UDP,53/TCP 8m. So, let’s edit the nginx. 4, Minikube v0. Kubernetes (K8s) is an open-source system for automating deployment, scaling, and management of containerized applications. By default, each replica set member uses the Kubernetes Pod’s FQDN (*. Kubernetes ReplicaSet is a resource that is used to manage the desired state of a group of replicas (pods). A MongoDB replica set made up of the Pods in the StatefulSet. But I can only rephrase what I wrote in my previous post. It. Scaling Your Application: An application can either be scaled up or down depending on the situation in two ways. All fine till here. Pour ReplicaSets, l'attribut kind est toujours ReplicaSet. ช่วงนี้หลายๆ คนอาจจะได้ยินชื่อ Kubernetes บ่อยๆ ว่าเป็น tools ที่. A Node. 2. initially, you must deploy a kubernetes cluster on gke, which can be. extensions/frontend scaled master $ kubectl get pods NAME READY STATUS RESTARTS AGE frontend-4jb2x 1/1 Terminating 0 38s frontend. Let’s summarize. If we execute the commands: kubectl get sts mongodb and kubectl get pods -l app=mongodb , we see the cluster deployed. The most common use cases for running databases in Kubernetes are: Create a private Database as a Service (DBaaS). First your manifests will be applied then HPA will be respected. To set them on the command line, prepend the option name with “values. It provides features such as rolling updates, rollbacks, and scaling of the number of. How do you set-up Mongo replica set on Kubernetes? 2 Unable to create Mongo Replication Set in Kubernetes. After you have copied the data files from the "seed" source, start the mongod instance with a new members [n]. Configure Certificate Rotation for the Kubelet; Manage TLS. kubectl describe replicaset replicaset-name. Replica Set use Set-Based selectors while replication controllers use Equity. 0. Each pod in a StatefulSet backed by a Headless Service will have a stable DNS name. Viewed 1k times. 5 or later. ReplicaSet then fulfills its purpose by creating and deleting Pods as needed to reach the desired number. Now , you will need to either delete the replica sets or delete the existing pods: kubectl delete rs new-replica-set kubectl delete pod pod_1 pod_2 pod_2 pod_4. kubectl config set-credentials − Sets a user entry in kubeconfig. In managed clusters you don't always have read access to the kube-system scheduler logs . It is not terminating the two older pods: kubectl get pods NAME READY STATUS RESTARTS AGE nfs-server-r6g6w 1/1 Running 0 2h redis-679c597dd-67rgw 1/1 Running 0 2h wordpress-64c944d9bd-dvnwh 4/4 Running 3 3h wordpress-64c944d9bd-vmrdd 4/4 Running 3 3h wordpress-f59c459fd-qkfrt 0/4. 今回はいよいよReplicaSetとDeploymentについて。 ReplicaSetについて. Kubernetes synergizes with MongoDB to create highly scalable and portable database deployments. Also Read: A Complete Guide to Kubernetes Secrets. Alternatively, you can also specify the replica set name and the ip addresses in a configuration file: replication: replSetName: "rs0". Once it is submitted, the Kubernetes cluster will create the pods and ReplicaSet. Learn more about Kubernetes. status (). apps | grep "0 0 0" | cut -d' ' -f 1) This only works because of the way kubectl get all displays resources. A ReplicaSet ensures that a specified number of pod replicas are running at any given time. Longhorn implements distributed block storage using containers and microservices. If the certificate authority is not present on your workstation, you can. It will wait for the MongoDB Replica Set member to fully boot up and create the. The rollout restart command is used to restart a deployment or a replica set in Kubernetes. I've tried. In order to get this to work, you will need to have the mongod nodes isMaster command return a different set of hostnames depending on where the client request is coming from. If you want this to work properly on GKE just change the storage class portion. When you deploy multiple replica sets using this method, you must make sure they each have a unique value for scramCredentialsSecretName. For backwards compatibility, the previous Helm installation options, with the exception of Kubernetes resource settings, are also fully supported. Pods in Kubernetes are not fault tolerant by default. kubectl delete -f . When the control plane creates new Pods for a ReplicaSet, the . 与所有其他 Kubernetes API 对象一样,ReplicaSet 也需要 apiVersion 、 kind 、和 metadata 字段。. Unlike a Deployment, a StatefulSet. Replica Set is the next generation of Replication Controller. For any queries, feel free to contact me at yatharth. We need k8s to automatically start a pod if the pod prematurely dies or when a node failure happens. Running Mongodb As A Microservice With Docker And Kubernetes Andrew Instructions the steps to create a docker cluster are as follows. Step2: Check the Context is set to your newly created cluster. . MySQL settings remain on insecure defaults to. We can set revisionHistoryLimit to specify how many old replicaSet s we want to retain:. OwnerReferences[0]. The replicaset with revision N-1 will be the "old" one. The kube-controller-manager is responsible for running the Deployment Controller, which connects to the api-server, consumes Deployments and manages ReplicaSets. For many applications with usage that varies over time, you may want to add or remove pod replicas in response to. Assuming deployment, replicaSet and pod are all 1:1:1 mapping. I would say that you have issue with DNS configuration (No host described in new configuration 1 for replica set rs0 maps to this node). Follow. Configure Certificate Rotation for the Kubelet; Manage TLS. Also check out An Introduction to Service Meshes for information about how service meshes like Istio. Creating and Setup Kubernetes Replica Set. So, Imagine that a microservice has two replicas and it is running on a namespaces with two. ; You can use the operator field to specify a. When Pods are being deleted, they are terminated in reverse order, from {N-1. Try kind: Deployment. g. Here is a summary of the process: You, as cluster administrator, create a PersistentVolume backed by physical storage. It should reflect the desired replica count you scaled to. Kubernetes is a scalable container orchestrator that helps you build fault-tolerant, cloud native applications. Last modified August 24, 2023 at 6:38 PM PST: Use code_sample shortcode instead of code shortcode (e8b136c3b3) Use kubectl patch to update Kubernetes API objects in place. 2 # Number of replica sets to create security: authentication: modes: - SCRAM statefulSet: Replace <your-password. Kubernetes offers a DNS cluster addon Service that automatically assigns dns names to other Services. _id and allow it to apply all operations from the oplog until it reflects the current state of the replica set. It manages the lifecycle of pods and provides a way to scale and maintain the desired state of the application. ReplicaSets work to maintain the desired state of a set of identical pods, ensuring that if the actual state deviates from the desired state (due to failures or scaling needs), the ReplicaSet takes appropriate actions to bring the system back to the desired state. The service name in the stateful set matches the name of the headless serice, the statefulset itself works as expected and nslookup as well as kubectl describe svc/mongodb-headless -n mongo produce correct hostname to IP address mapping. The Operator automates configuration of Source and Replica Percona XtraDB Clusters,. desired: Number of desired pods: gauge: kubernetes. Install suggested plugins - to install the recommended set. Only the following resource creation is possible using kubectl create:. ReplicaSets Controller uses set-based selectors to manage the pods. updateSecrets. So we tell Kubernetes, “I would like a replica set named web, which should have 3 pods, all matching the following specification. I am developing an application for dealing with kubernetes runtime microservices. Kind you can write code to find the Pod manager/controller depending on the type (ReplicaSet, DaemonSet, etc). Administrar la federación de clústeres; Networking. Selectors use labels to filter/select objects . A replica set is a group of MongoDB deployments that maintain the same data set. If any Pod dies, then the controller will re-create a new one by watching the Pod status. ymlAlternatively, you can also specify the replica set name and the ip addresses in a configuration file: replication: replSetName: "rs0". The difference between a replica set and a replication controller is that a replica set supports set-based selector requirements whereas a replication controller only supports equality-based selector requirements. with the -A option it gives you all your hpa from all namespaces if you want to specify a namespace, you can use -n option. NET Core APIs from Angular. To check your version of Kubernetes, run kubectl version. Kubernetes nodes use internal. 2. available: Total number of available pods (ready for at least minReadySeconds) targeted by this replica set. Kubernetes — Replica Sets Replica Set ensures how many replicas of the pod should be running. Install multi-cloud container storage solution like Portworx. svc. In this tutorial, I will be using v0. As with all other Kubernetes API objects, a ReplicaSet needs the apiVersion, kind, and metadata fields. In practice, all of these solutions can feet my needs, but I don't know if there are best practices for this case. Establishes TLS -encrypted connections between client applications and MongoDB. This tutorial will teach you how to deploy MongoDB on Kubernetes. Sure there is. The amount of seconds Kubernetes will wait for a clean replica set Pods termination: Key: replsets. We will use the MongoDB Community Kubernetes Operator . But only one replicaSet (the latest one) should be showing the number of pods; all other older sets should be showing 0. A ReplicaSet is one of the Kubernetes controllers that makes sure we have a specified number of pod replicas running. Kubectl Scale use cases. Update your replica set resource YAML file. Teams. Rolling updates allow Deployments' update to take place with zero downtime by incrementally updating Pods instances with new ones. then apply it to the cluster with: kubectl apply -f k8-deployment. Sorted by: 4. 152. labelSelector. As such, it is often used to guarantee the availability of a specified number of identical Pods. Step1: Creating a GKE Cluster with 3 nodes. Call the ASP. 0. The API version apps/v1beta2 is. 1 Answer. What is Kubernetes ReplicaSet? A ReplicaSet (RS) is a Kubernetes object that ensures there is always a stable set of running pods for a specific workload. template for a Replica Set. The key difference between the replica set and the replication controller is, the replication controller only supports equality-based selector whereas the replica set supports set-based selector. In Kubernetes, a ReplicaSet is responsible for maintaining the desired number of replicas of a pod to ensure high availability and load balancing in handling traffic. replicas of the Deployment and / or StatefulSet be removed from their manifest (s). kubectl scale --replicas=10 -f rs-creation. We would like to show you a description here but the site won’t allow us. You can see them with this command: kubectl get pods NAME READY STATUS RESTARTS AGE mongo-0 2/2 Running 0 3m mongo-1 2/2 Running 0 3m mongo-2 2/2 Running 0 3m. Step3: list the nodes of the cluster. $ kubectl exec -it mongod-0 -c mongod-container-app bash. Therefore, unless the pod was not created using a controller, Kubernetes will not be able to recover it if a pod crashes inside your Node. status() instruction. You can check if it's running on your cluster: kubectl get services kube-dns --namespace=kube-system. ReplicationController will maintain the pod lifecycle by making sure that the desired is matching with no. Let’s explore both the procedure step by step. You should now have a running replica set. More precisely, a Deployment creates a ReplicaSet which then creates a set of identical, steteless, pods, w. What is Replica Set ? A ReplicaSet (RS) is an object in kubernetes that ensures there is always a desired number of pods running. 1. g environment = production or tier != frontend) which is what you use with replication controller. ReplicaSet is a Kubernetes object that maintains the stability of Pods, it guarantees the availability of Pods depending on the replica number provided by a config file. 今回はworkloadsリソースの一つreplicasetについてWorkloadsリソースクラスタ上にコンテナを起動させるためのリソース。. NAME READY STATUS RESTARTS AGE guestbook-redis-replica-2q2yf 1/1 Running 0 3m guestbook-redis-replica-qgazl 1/1 Running 0 3m Updating labels. "someMongoUser" - name: MONGO_INITDB_ROOT_PASSWORD value: "somePassword" - name: MONGO_REPLICA_SET value: "myReplicaSet" - name: MONGO_PORT value:. I highly recommend reading it all. By evaluating pod. save the file. Using Community Kubernetes Operator. Running Mongodb As A Microservice With Docker And Kubernetes Andrew. EDIT: Actually, this didn't fix the entire problem. name of the ReplicaSet is part of the basis for naming those Pods. Pods (and, by extension, containers) are, nevertheless, short-lived entities. I even connect it to my mongo-express client. My ports in compose look like: ports extract docker-compose. It creates 3 Pods (one for each Set) with a volume to keep the data statefully. If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data. 1:27017:27017. connectivity. You cannot create replicaset using the command line. For example, if a web application requires at least. kubectl get nodes -o wide MongoDB® nodes port: You will have a different node port for each MongoDB® node. <externalDomain>The replica set controller detected that and created a new Pod to match the replicas' desired number (5). We recommend deploying one SQL Server container (instance) per pod in Kubernetes. The easiest way to scale an existing ReplicaSets on a Kubernetes cluster is to use the Kubectl command-line and quickly scale up or down the number of pods. In a nutshell, you run a sidecar app to configure the replica set for you, and either use a service per instance or ping the K8s API for the pod IP addresses. But an RS ( ReplicaSet) set-based label selector like “in, notin, exist”. gz StatefulSets. A ReplicaSet's purpose is to maintain a stable set of replica Pods running at any given time. yaml’, and we will be. Even though the new replica set is created. From the mongo shell, run the full rs. Behavior. kubectl get pods NAME READY STATUS RESTARTS AGE my-app-replica-set-5c6b9bf7d8-6q8f2. Kubernetes deployments manage stateless services running on your cluster (as opposed to for example StatefulSets which manage stateful services). Port forward to access mongo on local: 3 Answers. Figure 1: Three-node MongoDB replica set Important : The documentation states the following. replicas to 2. Defaults to 1. Create a Replicaset; Create a Replicaset. Copy. Since kubernetes 1. Example-2: Create replica set using match expressions. yaml replicaset. A value of 1 indicates the member votes, while a value of 0 indicates that the member does not vote. Statefulsets is used for Stateful applications, each replica of. using replica set you can easily run multiple pods of given instances. local. g Hadoop cluster, MySQL cluster, where each node has its own storage. The challenge I am having is that, I want to be able to loop through all the deployments and save their name and number of replicas so I scale them back to the original after scaling down. 10. To see the current status of the replica set, use rs. 9 the API version apps/v1 on the ReplicaSet kind is the current version and is enabled by default. Deployment 特性. This enables the Kubernetes Operator to react to changes that you make to the ConfigMap or the secret. A ReplicaSet (RS) is a Kubernetes object used to maintain a stable set of replicated pods running within a cluster at any given time. A ReplicaSet is defined with fields, including a selector that specifies how to identify Pods it can acquire, a numberof replicas indicating how many Pods it should be maintaining, and a pod template specifying the data of. extensions/frontend scaled master $ kubectl get pods NAME READY STATUS RESTARTS AGE frontend-4jb2x 1/1 Terminating 0 38s frontend-98xkj 0/1. Once the commands run, Kubernetes will action the. For example, the following command overrides the pilot. Usually, you define a Deployment and let that Deployment manage ReplicaSets automatically. Seperti objek API Kubernetes lainnya, sebuah ReplicaSet membutuhkan field apiVersion, kind, dan metadata. A replica set is a lower-level abstraction that provides basic scaling mechanisms for pods. TLS certificate; TLS key; CA key; TLS Certificate must contain DNS names of all your replica sets in Subject Alternative Name (SAN) sectionI assume that you want the default 'rolling upgrade' behavior of Deployments: they create a new replica set and start it before the old one is drained (rolling upgrade). e. The following kubectl command sets the spec with progressDeadlineSeconds to make the controller report lack of progress of a rollout for a Deployment after 10 minutes: kubectl patch deployment/nginx-deployment -p ' {"spec": {"progressDeadlineSeconds":600}}'. Let's try something different now. Each of these sets is what’s called a Kubernetes object. There are several strategies when it comes to deploying apps into production. The guide includes steps to run a standalone MongoDB instance and a replica set. En la versión 1. io/revision: "4" This will exist on both the deployment and the replicaset. A Replica set is used to ensure that a specific set of Pods is running at all times. TL;DR: Kubernetes has a built-in rollback mechanism. master $ kubectl scale rs frontend --replicas 2 replicaset. Taken from Kubernetes website: "A ReplicaSet's purpose is to maintain a stable set of replica Pods running at any given time. A deployment is an object in Kubernetes that lets you manage a set of identical pods. CONFIG_SVR: NO: false: Configures the configsvr variable when initializing the replicaset. The Replication Controller is the original form of replication in Kubernetes. mongodb-service.