DevOps/Kubernetes
[Kubernetes][CKA] ETCD
박한결
2023. 12. 13. 00:16
Overview of ETCD
- Definition: ETCD is a distributed, reliable key-value store that is simple, secure, and fast. It is primarily used in clustered environments for configuration and state management.
- Key-Value Store Explained: Unlike traditional databases that use tables, ETCD stores data in a key-value format. Each key-value pair (or 'document') can have a different structure, and changes to one document do not affect others.
Installation of ETCD
- Process:
- Download ETCD binaries.
- Extract the binaries.
- Run the ETCD service.
- Default Control: ETCD controller client is typically the default interface for interacting with ETCD.
ETCD Versions
- Version 2: Widely used, with a stable API.
- Version 3: Introduced significant changes, including modifications to the API.
- etcdctl: This is a command-line tool designed to work irrespective of the ETCD API version. Key versions to check are the etcdctl version and the API version.
- Version Switching: The ETCDCTL_API environment variable allows switching between different API versions.
ETCD's Role in Kubernetes
- Function: Stores information about the Kubernetes cluster, including nodes, pods, configs, secrets, accounts, roles, bindings, and other data. ( 쿠버네티스 클러스터에 대한 정보 -nodes, pods, configs, secrets, accounts, roles, bindings 등-를 저장 )
- Operation: Every operation in the cluster updates the ETCD server, and an operation is considered complete only after this update. ( 클러스터 내의 모든 작업은 ETCD 서버를 업데이트하며, 이 업데이트가 완료되면 작업이 완료된 것으로 간주 )
Kubeadm
- Definition: Kubeadm is a tool for quickly installing and setting up a basic Kubernetes cluster. ( Kubeadm은 기본 쿠버네티스 클러스터를 빠르게 설치하고 설정하는 도구 )
- ETCD Integration: Kubeadm can be used to set up ETCD as part of the Kubernetes cluster initialization process.
High Availability (HA) with ETCD
- Multiple Master Nodes: In an HA setup, multiple master nodes are used to ensure cluster availability and resilience. ( HA 설정에서는 클러스터 가용성과 탄력성을 보장하기 위해 여러 마스터 노드가 사용됨 )
- ETCD Configuration for HA:
- Cluster Configuration: ETCD clusters need to be configured to work in sync across multiple master nodes.
- advertise-client-urls: This parameter in ETCD configuration plays a critical role in defining how ETCD communicates with the Kubernetes cluster.
- ETCD Cluster Health: Regular checks and maintenance of the ETCD cluster are vital for HA environments.
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ETCD ?
distributed reliable key-value store that is simple, secure and fast
Key-Value Store ?
traditional database : table format
key-value : document
each file has different structure
one file does not effect to other file
install ETCD
order : download binaries - extract - run ETCD service
default controller : ETCD controller client
ETCD versions
version2 - 많이 사용함
version3 - 변화가 많았음 ( api version 이 바뀜 => etcdctl 명령어도 바뀜 )
etcdctl 은 api 버전에 관계 없이 동작하도록 설계 되어있음
확인해야 하는 버전은 etcdctl version, api version 두 개가 있음
ETCDCTL_API 환경변수를 사용하면 버전을 바꿀 수 있음
ETCD roles in Kubernetes
쿠버네티스 클러스터에 대한 정보를 저장
(Nodes, PODs, Configs, Secrets, Accounts, Roles, Bindings, Others )
클러스터에서 작업을 할 때 마다 ETCD 서버에 업데이트가 되고, 업데이트가 완료되야 작업이 완료된 것으로 간주됨
* advertise-client-urls
Kubeadm
HA
multiple master nodes
etcd configuration
실습