Kubernetes

Kubernetes Work Units

Pods Services Replication Controllers Labels

Kubelet

Responsible for relaying information to and from the master server, as well as interacting with the etcd store to read configuration details or write new values.Work is received in the form of a "manifest" which defines the workload and the operating parameters. The kubelet process then assumes responsibility for maintaining the state of the work on the minion server.

Etcd

store configuration data and service discovery

Master server components

Etcd API server Controller Manager Server Scheduler Server

Proxy Service

This process forwards requests to the correct containers, can do primitive load balancing, and is generally responsible for making sure the networking environment is predictable and accessible, but isolated.

Replication Controllers

a framework for defining pods that are meant to be horizontally scaled.

cluster

a group of servers and other resources that act like a single system

horizontally scaled pods

a pod that's gonna grow across nodes

Kubernetes

a system built by google manage containerized apps in a clustered environment related, distributed components across varied infrastructure

Services

a unit that acts as a basic load balancer and ambassador for other containers. it is an interface to a group of containers so that consumers do not have to worry about anything beyond a single access location

API server

allows a user to configure K8s workloads, ensures etcd store and the service details of deployed containers are in agreement

Labels

arbitrary tag that can be placed on the above work units to mark them as a part of a group. given as key-value pairs

Scheduler Server

assigns workloads to specific nodes in the cluster. reads in a service's operating requirements, analyze the current infrastructure environment, and place the work on an acceptable node or nodes. tracking resource utilization on each host to make sure that workloads are not scheduled in excess of the available resources.

Pod

closely related containers that should be controlled as a single "application". managed as a unit and they share an environment and are scheduled on the same host.

Minion Server Components

container runtime Kubelet Proxy Service

Service discovery

determines the IP and port for a service that exist on multiple hosts

Controller Manager Server

handles the replication processes, details of the operations are written to etcd, where the controller manager watches for changes. When a change is seen, the controller manager reads the new information and implements the replication procedure that fulfills the desired state.