willems
/
Summaries
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
Summaries/Overig/kubernetes/Intro Basis Components of K...

2.5 KiB
Raw Blame History

title updated created latitude longitude altitude
Intro Basis Components of K8s 2022-02-05 15:10:02Z 2022-01-29 15:33:56Z 52.38660000 5.27820000 0.0000

What is Kubernetes (K8s)

  • container orchestration tool
  • manages containers (not only Docker)
  • different environments
    • physical
    • virtual
    • cloud

What problems solves Kubernetes:

  • manages many containers with independent services, like micro services

Kubernetes features

  • High Availability (no downtime)
  • Scalability (high performance)
  • Disaster recovery (backup and restore)

Kubernetes components (but many more)

  • Node (physical or virtual)
    • node contains pods and per pod usually 1 application
    • pod is smallest unit of K8s
    • pod is abstraction over container
    • each pod gets its own ip-address
    • new ip-address on re-creation
    • aca7155a4c7e4f2b982378cbb2d37400.png
  • Services
    • permanent ip-address
    • lifecycle of Pod and Service are not connected
    • ad9e649d35df7e77ce73056bbaf2cbb9.png
  • External Service
    • opens the communication for external sources
    • internal service for eq database. Not accessible from outside
    • External request go first to Ingress (to route traffic)
    • 25f981495ea54faccfe5ea58cd1f8b75.png
  • ConfigMap & Secret
    • external configuration of application (eq URL of a database DB_URL = mongo-db-service)
    • secret credentials in Secret (like configMap but base64 encoded)
    • Application can read from ConfigMap and Secret
  • Volumes
    • for persistent data
    • attach physical storage to a pod
    • local machine or remote storage (eq cloud and outside k8s cluster)
    • k8s does not manage data persistence
  • Deployment and Stateful Set
    • Every Pod is replicated as specified in BluePrint
    • Service has 2 functionalities:
      • Permanent IP (so an other pod can connect of the pod dies)
      • load balancer
      • the pod is not created, but for every pod is specified (Blueprint) how many replicas are required
        • Blueprint is abstraction of Pods. Pods are an abstraction of Containers
        • In practice just working with Deployments
      • Stateful Set
        • Databases have state and can not be replicated
        • For stateful applications like databases
        • no database inconsistency can occur.
        • is not easy therefor advice to host databases outside K8s cluster