Spread the loveAs we already know, what is a container and why we need it, in my previous post ,
As we already know, what is a container and why we need it, in my previous post , lets talk about the next step into containerization journey.
The first question comes in everybody’s mind is “why we need Container Management tool ” separately when we are already using docker. So think about the situation where you are managing 10 – 40 or even 100 containers for your deployments, you still may be able to manage them by your own (manually or individually).
But what about the situation when an organization has 2000 or 20000 plus containers, manually management of those tools will be impossible or difficult. There we have container management tools available to rescue us and mange our containers, for example : if a container die due to whatsoever reason, it’s the responsibility of management layer to bring it back or spin a new one on it’s behalf.
In openshift we have few primary terms,
- Container – A docker container, which host actual logic.
- Kubernetes – Container management tool and heart of openshift.
- POD – Collection of one or more containers, and a wrapper around it.
- ETCD – Key value data store, to retain openshift cluster status.
- Router – Instance of HA Proxy, wrapped by openshift and renamed as router.
- Registry – Place / Tool used to store docker images locally.
- Project – Isolated space, where we can build and deploy inter-related application component and services.
So, in simple words, openshift using kubernetes as it’s container management, Kubernetes has one and more pod to host the applications, and a single pod may have more than one action running containers.
In openshift cluster, generally we have three type of nodes (VM), Master Nodes, Infra-nodes & worker / application nodes.
Master nodes are provides administrative functionality and should be in odd numbers to maintain the etcd key store quorum, Infra-nodes hosts router and registry pods and worker nodes are dedicated for customer applications.
Openshift is not limited to only running and managing the running containers, it’s much more than that. it will be configured with back-end storage and provides persistent volumes (PV) to containers, we may enforce resource management using “Limit and Quotas” . self-healing of containers are the characteristics of Kubernetes.
Whenever business demands, we can add/scale additional nodes to the existing openshift cluster without any downtime.