Free and Premium SAP C_KYMD_01 Dumps Questions Answers

Kubernetes pods are the smallest deployable units of computing that you can create and manage in Kubernetes. A pod is a group of one or more containers, with shared storage and network resources, and a specification for how to run the containers. Pods are the atomic unit on the Kubernetes platform. Pods are not permanent units in Kubernetes. They can be terminated and replaced anytime, either by the user or by the system. Pods are ephemeral and disposable entities that are created and destroyed dynamically. Pods can be scaled up or down, migrated across nodes, or rescheduled due to failures or maintenance. Pods cannot contain deployments. Deployments are higher-level resources that manage pods and provide declarative updates to them. A deployment can create multiple pods from the same template and ensure that the desired number of pods are always available. A pod can only contain containers and volumes, not other Kubernetes resources. References: Pods | Kubernetes, Viewing Pods and Nodes | Kubernetes, What is a Kubernetes pod? - Red Hat, What are Pods in Kubernetes? - Medium, Network overview | Google Kubernetes Engine (GKE) | Google Cloud.

When you create an API Rule for a service, the API Gateway Controller creates an Istio Virtual Service for you behind the kyma-gateway. The Istio Virtual Service defines the rules that control how requests for a service are routed within an Istio service mesh. By creating an API Rule, you have a higher-level abstraction of Istio VirtualServices and Oathkeeper Access Rules that allows you to provision services quickly and securely. References: Using the API Gateway to Expose Services, Exposing a Service in Kyma with API Rules

• The API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane. The main implementation of a Kubernetes API server is kube-apiserver . kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. You can run several instances of kube-apiserver and balance traffic between those instances. etcd Consistent and highly-available key value store used as Kubernetes’ backing store for all clusterdata. If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data2.
• You use etcd in Kubernetes as a backend for service delivery. It is one of the master components used for cluster management. You can run etcd in an external cluster or as a pod on your Kubernetes master. If you run it as an external cluster you can benefit from an extra layer of security and resiliency due to its isolation from the master3.

References:

• Operating etcd clusters for Kubernetes
• Kubernetes Components
• What Is etcd and How Is it Used in Kubernetes?

Pods are created in a sequential order when a StatefulSet is set up. This means that for a StatefulSet with N replicas, the Pods are deployed one by one, starting from the Pod with the index 0 and ending with the Pod with the index N-1. Each Pod has to be in the Running and Ready state before the next Pod is created. This ensures that the Pods have a predictable and unique identity and can be connected to their corresponding persistent volumes. References: 

The command kubectl get services lists all the services in the current namespace1. The get command is used to display one or more resources in Kubernetes2. The services argument specifies the type of resource to list. To list services in a differentnamespace, you can use the --namespace or -n flag3. References: Kubectl commands to list services, deployments and pods from namespace …, kubectl Cheat Sheet | Kubernetes, How to get the current namespace of current context using kubectl - Stack Overflow

 A one off/non parallel job is a workload type that runs a single task to completion and then terminates. This is suitable for running a database migration on SAP BTP, Kyma runtime, as it does not require scaling, persistence, or parallelism. A parallel job, on the other hand, is a workload type that runs multiple tasks in parallel and then terminates. This is useful for batch processing or data analysis, but not for database migration. A StatefulSet is a workload type that runs one or more pods that maintain a stable identity and persistent storage. This is useful for stateful applications such as databases or message brokers, but not for database migration. A DaemonSet is a workload type that runs one pod on each node in the cluster. This is useful for providing node-level services such as logging or monitoring, but not for database migration. References: Workload Concepts, Kubernetes Workloads

 You can check which SAP BTP services are available to create in your subaccount by visiting the SAP BTP Service Marketplace. The Service Marketplace is a page in the SAP BTP cockpit that lists all the services and applications that you can use in your subaccount. You can browse, search, filter, and sort the services and applications by categories, such as databases, analytics, integration, or security. You can also see the details, documentation, and pricing of each service and application, and create instances or subscriptions from the Service Marketplace. The Service Marketplace shows only the services and applications that you have entitlements for in your subaccount. You can manage your entitlements from the Entitlements page in the SAP BTP cockpit. References: SAP BTP Service Marketplace, Create a Service Instance in SAP BTP, Add a New Entitlement to Your Subaccount

• A headless service is defined by setting the clusterIP field to None in the service spec. This tells Kubernetes not to allocate a cluster IP for the service, and to create DNS records only.
• For StatefulSets, you can use a headless service to control the domain of the pods. The pods that belong to a StatefulSet have a unique identity that is comprised of an ordinal, a stable network identity, and stable storage. The identity sticks to the pod, regardless of which node it’s (re)scheduled on.
• Each pod in a StatefulSet derives its hostname from the name of the StatefulSet and the ordinal of the pod. The pattern for the constructed hostname is (statefulsetname)−(ordinal). The example above will create three pods named web-0,web-1,web-2.
• A StatefulSet can use a headless service to provide network identity for its pods. The service is responsible for creating a DNS record for each pod in the form (podname).(governing service domain). For the previous example, the headless service named nginx will create DNS records for web-0.nginx, web-1.nginx, and web-2.nginx.

References:

• Headless Services
• StatefulSets
• Is it required to use a headless service for statefulsets?

 A Persistent Volume Claim (PVC) is a request for storage by a user. It is similar to a Pod, which is a request for compute resources by a user. A PVC enables a Pod to consume a slice of the available storage in the cluster without knowing the details of the underlying storage infrastructure. A PVC is associated with a StorageClass, which defines the type and characteristics of the storage. A PVC is also bound to a Persistent Volume (PV), which is an abstraction of the physical or cloud-based storage resource. A PV is created by the cluster administrator and has a lifecycle independent of any Pod. A PVC can specify the size, access mode, and storage class of the PV it requires. Before deploying an application that needs persistent state, a user must create a PVC for the Pod that will run the application. The PVC will then be automatically bound to a suitable PV by the cluster, or dynamically provisioned if the storage class supports it. The Pod can then mount the PVC as a volumeand access the persistent storage12345. References: Persistent Volumes | Kubernetes, How Kubernetes Persistent Volume Claims Work - CBT Nuggets, Exploring Kubernetes Storage: Persistent Volumes and Persistent Volume Claims - Atatus, Configure a Pod to Use a PersistentVolume for Storage | Kubernetes, kubernetes - How to mount a persistent volume on a Deployment/Pod using PersistentVolumeClaim? - Stack Overflow.

 Some of the features of Kubernetes are:

• Immutability and self-healing: Kubernetes treats pods as immutable, meaning that they are not modified after they are created. Instead, pods are replaced with new ones when they need to be updated or repaired. This ensures that the pods are always in a consistent and predictable state. Kubernetes also monitors the health and availability of the pods and automatically restarts, reschedules, or replicates them if they fail or become unresponsive1.
• Extensibility and ecosystem: Kubernetes is designed to be extensible and modular, allowing users to customize and extend its functionality according to their needs. Kubernetes supports various extensions, such as custom resources, operators, admission controllers, schedulers, network plugins, storage plugins, and more. Kubernetes also has a large and vibrant ecosystem of tools, services, and applications that are built on top of or integrate with it2.
• Automated rollouts and rollbacks: Kubernetes enables users to deploy and update their applications with zero downtime, using declarative configuration and rolling updates. Kubernetes ensures that only a certain number of pods are changed at a time, and that the new pods are ready before terminating the old ones. Kubernetes also tracks the history of each update and allows users to roll back to a previous version if something goes wrong3.

References:

• 1: Pods | Kubernetes
• 2: Extending Kubernetes | Kubernetes
• 3: Deployments | Kubernetes

 The kubectl command to list pods with the exact label “env-dev” is kubectl get pods -l env=dev. The -l or --selector flag allows you to filter pods by label selectors, which are key-value pairs that are attached to pods. The = operator matches pods that have the exact label value specified. The -L or --label-columns flag adds a column with the value of the specified label(s) to the output, but does not filter the pods. The -I or --ignore-not-found flag returns an exit code of 0 when no resources are found, but does not affect the output. The -l env-dev flag is invalid, as it does not specify a label value. References: 6, 7, 9

 The API Gateway in Kyma is a custom-configured Istio Ingress Gateway that is installed in the kyma-system namespace called kyma-gateway. Istio is an open-source project that provides a service mesh for microservices. It enables traffic management, security, observability, and policy enforcement for the services in the cluster. The API Gateway uses Istio resources to expose and secure APIs for the workloads in Kyma. References: Using the API Gateway to Expose Services, SAP BTP, Kyma Runtime API Gateway future architecture based on Istio, GitHub - kyma-project/api-gateway.

Observability tools are used to monitor system behaviour and performance, as well as to troubleshoot issues and identify root causes. Observability tools in SAP BTP, Kyma runtime include Grafana, Prometheus, Loki, and Jaeger, which provide dashboards, metrics, logs, and traces for the workloads running in the cluster1. Distributed tracing is a technique to track the flow of requests across microservices and visualize the latency, errors, and dependencies of each service2. Observability tools help developers and operators to ensure the reliability, availability, and security of their applications and services. 

Kyma Eventing simplifies the process of publishing and subscribing to events in the cluster. Publishing events means sending information about a change in the state of the application or the system to the Eventing backend. Subscribing to events means registering interest for a specific event type from a specific source. Kyma Eventing allows users to publish events by sending HTTP requests to the Event Publisher Proxy component, which validates and forwards the events to the NATS backend. Kyma Eventing also allows users to subscribe to events by creating Subscription custom resources that specify the event source, type, and the HTTP endpoint of the service that will receive the events. Kyma Eventing handles the delivery of the events from the NATS backend to the subscribers with the help of the Eventing Controller and the Eventing Dispatcher components. References: 

 A service mesh in Kyma typically consists of two components: the data plane and the control plane12. The data plane is responsible for handling the communication between the microservices in the cluster. It consists of a set of sidecar proxies (Envoy) that are injected into each pod and intercept the traffic. The control plane is responsible for managing the configuration and policies of the data plane. It consists of a set of components (Istio) that provide features like service discovery, security, traffic management, observability, and more12. References: Discovering the Service Mesh, SAP BTP – KYMA – SERVICE MESH | SAP Blogs

 The service mesh solution in SAP BTP, Kyma runtime is based on Istio, which is one of the most popular service mesh solutions. Istio uses the Sidecar proxy pattern, which means that a proxy is deployed as a sidecar container next to each service. This way, the proxy can intercept and manage the traffic between the services, without requiring any changes in the application code. The proxy also communicates with the Istio control plane, whichprovides configuration and policies for the service mesh. The other options are not valid proxy patterns for the service mesh solution in SAP BTP, Kyma runtime. References: Discovering the Service Mesh - SAP Learning, Istio Documentation - What is Istio?

kubectl is a command-line tool that allows you to run commands against Kubernetes clusters1. You can use kubectl in SAP BTP, Kyma runtime for the following purposes:

• To run interactive commands. kubectl supports various commands that let you interact with your cluster resources, such as creating, updating, deleting, describing, or executing them. For example, you can use kubectl create to create a resource from a file or kubectl exec to run a command in a container2.
• To view pod logs. kubectl allows you to view the logs of a pod or a container in a pod using the kubectl logs command. This can help you troubleshoot issues or monitor the pod activity3.
• To forward ports from remote machines to pods. kubectl enables you to forward one or more local ports to a pod using the kubectl port-forward command. This can allow you to access a pod from your local machine for debugging or testing purposes4.

References:

• 1: Kubernetes / Overview of kubectl
• 2: Kubernetes / kubectl Cheat Sheet
• 3: Kubernetes / Viewing logs
• 4: Kubernetes / Use Port Forwarding to Access Applications in a Cluster

When you delete a pod managed by a Replica Set, the Replica Set will schedule a new pod to replace the deleted one. This is because the Replica Set’s purpose is to maintain a stable set of replica pods running at any given time. As such, it is often used to guarantee the availability of a specified number of identical pods1. The Replica Set controller monitors the number of pods it owns and creates or deletes pods as needed to reach the desired number. The Replica Set identifies its pods by using a selector that matches the pods’ labels2. Therefore, deleting a pod will reduce the number of pods that match the selector, and trigger the Replica Set to create a new pod with the same pod template3.

References:

• 1: ReplicaSet | Kubernetes
• 2: Labels and Selectors | Kubernetes
• 3: Pods, Deployments and Replica Sets: Kubernetes Resources Explained