295 lines
8.8 KiB
Markdown
295 lines
8.8 KiB
Markdown
## OpenShift
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### OpenShift Exercises
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|Name|Topic|Objective & Instructions|Solution|Comments|
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|--------|--------|------|----|----|
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| Projects 101 | Projects | [Exercise](projects_101.md) | [Solution](solutions/projects_101.md)
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| My First Application | Applications | [Exercise](my_first_app.md) | [Solution](solutions/my_first_app.md)
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### OpenShift Self Assessment
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<details>
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<summary>What is OpenShift?</summary><br><b>
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OpenShift is a container orchestration platform based on Kubernetes.<br>
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It can be used for deploying applications while having minimal management overhead.
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</b></details>
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<details>
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<summary>How OpenShift is related to Kubernetes?</summary><br><b>
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OpenShift is build on top of Kubernetes while defining its own custom resources in addition to the built-in resources.
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</b></details>
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<details>
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<summary>True or False? OpenShift is a IaaS (infrastructure as a service) solution</summary><br><b>
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False. OpenShift is a PaaS (platform as a service) solution.
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</b></details>
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<details>
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<summary>True or False? OpenShift CLI supports everything kubectl supports, along with additional functionality</summary><br><b>
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True
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</b></details>
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<details>
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<summary>OpenShift supports many resources. How to get a list of all these resources?</summary><br><b>
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`oc api-resources`
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</b></details>
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<details>
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<summary>Explain OpenShift CLIs like <code>oc</code> and <code>odo</code></summary><br><b>
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oc is used for creating applications, but also for administrating OpenShift cluster<br>
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odo is used solely for managing applications on OpenShift (mainly from developers' perspective) and has nothing to do with administrating the cluster
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</b></details>
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## OpenShift - Architecture
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<details>
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<summary>What types of nodes OpenShift has?</summary><br><b>
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- Workers: Where the end-user applications are running
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- Masters: Responsible for managing the cluster
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</b></details>
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<details>
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<summary>Which component responsible for determining pod placement?</summary><br><b>
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The Scheduler.
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</b></details>
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<details>
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<summary>What else the scheduler responsible for except pod placement?</summary><br><b>
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Application high availability by spreading pod replicas between worker nodes
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</b></details>
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## OpenShift - Projects
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<details>
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<summary>What is a project in OpenShift?</summary><br><b>
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A project in OpenShift is a Kubernetes namespace with annotations.<br>
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In simpler words, think about it as an isolated environment for users to manage and organize their resources (like Pods, Deployments, Service, etc.).
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</b></details>
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<details>
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<summary>How to list all projects? What the "STATUS" column means in projects list output?</summary><br><b>
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`oc get projects` will list all projects. The "STATUS" column can be used to see which projects are currently active.
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</b></details>
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<details>
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<summary>You have a new team member and you would like to assign to him the "admin" role on your project in OpenShift. How to achieve that?</summary><br><b>
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`oc adm policy add-role-to-user <role> <user> -n <project>`
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</b></details>
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#### OpenShift - Applications
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<details>
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<summary>How to create a MySQL application using an image from Docker Hub?</summary><br><b>
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`oc new-app mysql`
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</b></details>
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#### OpenShift - Images
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<details>
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<summary>What is an image stream?</summary><br><b>
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</b></details>
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<details>
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<summary>What would be the best way to run and manage multiple OpenShift environments?</summary><br><b>
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Federation
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</b></details>
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#### OpenShift - Federation
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<details>
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<summary>What is OpenShift Federation?</summary><br><b>
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Management and deployment of services and workloads accross multiple independent clusters from a single API
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</b></details>
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<details>
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<summary>Explain the following in regards to Federation:
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* Multi Cluster
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* Federated Cluster
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* Host Cluster
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* Member Cluster
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</summary><br><b>
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* Multi Cluster - Multiple clusters deployed independently, not being aware of each other
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* Federated Cluster - Multiple clusters managed by the OpenShift Federation Control Plane
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* Host Cluster - The cluster that runs the Federation Control Plane
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* Member Cluster - Cluster that is part of the Federated Cluster and connected to Federation Control Plane
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</b></details>
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## OpenShift - Storage
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<details>
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<summary>What is a storage device? What storage devices are there?</summary><br><b>
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* Hard Disks
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* SSD
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* USB
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* Magnetic Tape
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</b></details>
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<details>
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<summary>What is Random Seek Time?</summary><br><b>
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The time it takes for a disk to reach the place where the data is located and read a single block/sector.
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Bones question: What is the random seek time in SSD and Magnetic Disk?
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Answer: Magnetic is about 10ms and SSD is somewhere between 0.08 and 0.16ms
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</b></details>
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#### OpenShift - Pods
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<details>
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<summary>What happens when a pod fails or exit due to container crash</summary><br><b>
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Master node automatically restarts the pod unless it fails too often.
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</b></details>
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<details>
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<summary>What happens when a pod fails too often?</summary><br><b>
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It's marked as bad by the master node and temporarly not restarted anymore.
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</b></details>
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<details>
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<summary>How to find out on which node a certain pod is running?</summary><br><b>
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`oc get po -o wide`
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</b></details>
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#### OpenShift - Services
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<details>
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<summary>Explain Services and their benefits</summary><br><b>
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- Services in OpenShift define access policy to one or more set of pods.<br>
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- They are connecting applications together by enabling communication between them
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- They provide permanent internal IP addresses and hostnames for applications
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- They are able to provide basic internal load balancing
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</b></details>
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#### OpenShift - Labels
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<details>
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<summary>Explain labels. What are they? When do you use them?</summary><br><b>
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- Labels are used to group or select API objects
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- They are simple key-value pairs and can be included in metadata of some objects
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- A common use case: group pods, services, deployments, ... all related to a certain application
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</b></details>
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#### OpenShift - Service Accounts
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<details>
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<summary>How to list Service Accounts?</summary><br><b>
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`oc get serviceaccounts`
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</b></details>
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#### OpenShift - Networking
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<details>
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<summary>What is a Route?</summary><br><b>
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A route is exposing a service by giving it hostname which is externally reachable
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</b></details>
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<details>
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<summary>What Route is consists of?</summary><br><b>
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- name
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- service selector
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- (optional) security configuration
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</b></details>
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<details>
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<summary>True or False? Router container can run only on the Master node</summary><br><b>
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False. It can run on any node.
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</b></details>
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<details>
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<summary>Given an example of how a router is used</summary><br><b>
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1. Client is using an address of application running on OpenShift
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2. DNS resolves to host running the router
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3. Router checks whether route exists
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4. Router proxies the request to the internal pod
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</b></details>
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#### OpenShift - Security
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<details>
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<summary>What are "Security Context Constraints"?</summary><br><b>
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From [OpenShift Docs](https://docs.openshift.com/container-platform/4.7/authentication/managing-security-context-constraints.html): "Similar to the way that RBAC resources control user access, administrators can use security context constraints (SCCs) to control permissions for pods".
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</b></details>
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<details>
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<summary>How to add the ability for the user `user1` to view the project `wonderland` assuming you are authorized to do so</summary><br><b>
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oc adm policy add-role-to-user view user1 -n wonderland
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</b></details>
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<details>
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<summary>How to check what is the current context?</summary><br><b>
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`oc whoami --show-context`
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</b></details>
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#### OpenShift - Serverless
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<details>
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<summary>What is OpenShift Serverless?</summary><br><b>
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- In general 'serverless' is a cloud computing model where scaling and provisioning is taken care for application developers, so they can focus on the development aspect rather infrastructure related tasks
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- OpenShift Serverless allows you to dynamically scale your applications and provides the ability to build event-driven applications, whether the sources are on Kubernetes, the cloud or on-premise solutions
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- OpenShift Serverless is based on the Knative project.
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</b></details>
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<details>
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<summary>What are some of the event sources you can use with OpenShift Serverless?</summary><br><b>
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* Kafka
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* Kubernetes APIs
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* AWS Kinesis
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* AWS SQS
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* JIRA
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* Slack
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More are supported and provided with OpenShift.
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</b></details>
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<details>
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<summary>Explain serverless functions</summary><br><b>
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</b></details>
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<details>
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<summary>What is the difference between Serverless Containers and Serverless functions?</summary><br><b>
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</b></details>
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#### OpenShift - Misc
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<details>
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<summary>What is Replication Controller?</summary><br><b>
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Replication Controller responsible for ensuring the specified number of pods is running at all times.<br>
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If more pods are running than needed -> it deletes some of them<br>
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If not enough pods are running -> it creates more
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</b></details>
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